Add the new low-level renderer, shared between the imm and scene graph renderer. LLR integration with the scene graph renderer not yet done.

26 files changed, 539 insertions, 536 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4b1ba6a..c480daf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -49,13 +49,14 @@ add_library(gfx SHARED
   src/core/shader_program.c
   src/core/shader.c
   src/core/texture.c
+  src/llr/llr.c
+  src/llr/light.c
+  src/llr/material.c
+  src/llr/mesh.c
   src/renderer/imm_renderer.c
   src/renderer/renderer.c
   src/scene/animation.c
   src/scene/camera.c
-  src/scene/light.c
-  src/scene/material.c
-  src/scene/mesh.c
   src/scene/model.c
   src/scene/node.c
   src/scene/object.c
diff --git a/README.md b/README.md
index f0b103d..491761d 100644
--- a/README.md
+++ b/README.md
@@ -20,32 +20,35 @@ educational purposes.
 ### Gfx
 
 The `Gfx` object represents the graphics subsystem and is at the center of the
-library's high-level API. The `Gfx` object exposes a `Render` backend and a
-`Renderer` and allows the caller to create `Scene`s.
+library's high-level API. The `Gfx` object exposes a render backend (`GfxCore`)
+and a `Renderer`, and allows the caller to create `Scene`s.
 
 ### Render Backend
 
-The `Render` backend is a thin abstraction layer over low-level graphics APIs
-like OpenGL or Vulkan. It holds GPU resources such as geometry, textures,
-shaders, etc, and exposes functions to manipulate them.
+The render backend (`GfxCore`) is a thin abstraction layer over low-level
+graphics APIs like OpenGL or Vulkan. It holds GPU resources such as geometry,
+textures, shaders, etc, and exposes functions to manipulate them.
 
-Currently there is only one implementation of the `Render` backend based on
+Currently, there is only one implementation of the render backend based on
 OpenGL.
 
 #### Ownership
 
-The `Render` backend owns all rendering resources: buffers, geometries,
-textures, shaders, etc. Even resources that point to other resources do not own
-those other resources (geometries pointing to buffers).
+The render backend owns all rendering resources: buffers, geometries, textures,
+shaders, etc. Even resources that point to other resources do not own those
+other resources (geometries pointing to buffers).
 
-There is no ownership tracking in the render backend. It is up to the client to
+There is no lifetime tracking in the render backend. It is up to the client to
 manage resource lifetime.
 
+### Low-level Renderer
+
+`ImmRenderer` is a low-level, immediate mode renderer.
+
 ### Scene
 
-A `Scene` encapsulates a scene graph. A scene graph contains the elements that
-make up a scene: nodes, cameras, lights, objects, etc. The current scene graph
-implementation includes:
+A `Scene` graph contains the elements that make up a scene. The current scene
+graph implementation includes:
 
 - Camera
 - Light
@@ -64,7 +67,8 @@ functions to set the parent node of an object/camera/light. If we exposed the
 former, the API could create the illusion that the hierarchy can be a DAG.
 
 The strict tree hierarchy should not be that restrictive in practice. Even the
-glTF 2.0 spec [enforces this](https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#nodes-and-hierarchy):
+glTF 2.0
+spec [enforces this](https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#nodes-and-hierarchy):
 
 > *For Version 2.0 conformance, the glTF node hierarchy is not a directed
 > acyclic graph (DAG) or scene graph, but a disjoint union of strict trees. That
@@ -76,9 +80,9 @@ glTF 2.0 spec [enforces this](https://github.com/KhronosGroup/glTF/blob/master/s
 Two use cases for instancing seem to be:
 
 1. Creating N identical clones, but each with a unique transform. (Ex: N
-animated characters animated in unison but located in different locations.)
+   animated characters animated in unison but located in different locations.)
 2. Creating N copies of a sub-tree, each now being their own unique tree. (Ex:
-The same N animated characters, but each of them now being animated separately.)
+   The same N animated characters, but each of them now being animated separately.)
 
 Some scene graphs
 ([Panda3D](https://docs.panda3d.org/1.10/python/programming/scene-graph/instancing))
@@ -87,10 +91,10 @@ to have multiple parents. This turns the scene graph into a DAG and adds a
 number of complications for us:
 
 1. Shared ownership of children. We would now need some sort of ref counting or
-deferred GC to delete nodes and their subtrees.
+   deferred GC to delete nodes and their subtrees.
 2. Nodes no longer have a unique parent.
 3. Given a node, we can no longer determine its location (which parent link do
-you follow?), or any attribute that is derived from its parent(s).
+   you follow?), or any attribute that is derived from its parent(s).
 
 In our case, we stick to strict tree hierarchies.
 
@@ -131,6 +135,10 @@ Code under `util/` provides functionality that need not be in the core part
 of the library (Gfx, render backend, scene or renderer). This includes functions
 to compute irradiance maps, create procedural geometry, etc.
 
+### Memory management
+
+TODO
+
 ## Ideas for Future Work
 
 - Render graphs to allow for custom multi-pass rendering algorithms.
diff --git a/include/gfx/gfx.h b/include/gfx/gfx.h
index 7c670a5..d5c25b6 100644
--- a/include/gfx/gfx.h
+++ b/include/gfx/gfx.h
@@ -3,6 +3,7 @@
 typedef struct AssetCache  AssetCache;
 typedef struct GfxCore     GfxCore;
 typedef struct ImmRenderer ImmRenderer;
+typedef struct LLR         LLR;
 typedef struct Renderer    Renderer;
 
 typedef struct Gfx Gfx;
@@ -16,12 +17,15 @@ void gfx_destroy(Gfx**);
 /// Get the render backend.
 GfxCore* gfx_get_core(Gfx*);
 
-/// Get the renderer.
+/// Get the scene renderer.
 Renderer* gfx_get_renderer(Gfx*);
 
 /// Get the immediate mode renderer.
 ImmRenderer* gfx_get_imm_renderer(Gfx*);
 
+/// Get the low-level renderer.
+LLR* gfx_get_llr(Gfx*);
+
 /// Get the asset cache.
 AssetCache* gfx_get_asset_cache(Gfx*);
 
diff --git a/include/gfx/llr/llr.h b/include/gfx/llr/llr.h
index 49b7706..57abffc 100644
--- a/include/gfx/llr/llr.h
+++ b/include/gfx/llr/llr.h
@@ -1,117 +1,64 @@
 #pragma once
 
-#include <math/aabb2.h>
-#include <math/aabb3.h>
 #include <math/camera.h>
 #include <math/mat4.h>
 #include <math/vec3.h>
-#include <math/vec4.h>
 
-typedef struct Anima    Anima;
-typedef struct Light    Light;
-typedef struct Mesh     Mesh;
-typedef struct Skeleton Skeleton;
+typedef struct Anima         Anima;
+typedef struct Geometry      Geometry;
+typedef struct Light         Light;
+typedef struct Mesh          Mesh;
+typedef struct ShaderProgram ShaderProgram;
+typedef struct Skeleton      Skeleton;
 
-typedef struct ImmRenderer ImmRenderer;
+typedef struct LLR LLR;
 
-/// Prepare the graphics systems for immediate-mode rendering.
-///
-/// Call this before issuing any immediate-mode rendering draws.
-void gfx_imm_start(ImmRenderer*);
-
-/// End immediate mode rendering.
-///
-/// Call this after issuing immediate-mode rendering draws and before swapping
-/// buffers.
-void gfx_imm_end(ImmRenderer*);
-
-// -----------------------------------------------------------------------------
-// Immediate-mode rendering of scene elements.
-//
-// This renders models and meshes under lighting. It is up to the client to
-// determine visibility, sort the calls optimally, etc.
+/// Set the shader to be used for subsequent draw calls.
+/// The shader is not yet activated at this point.
+void gfx_llr_set_shader(LLR*, ShaderProgram*);
 
 /// Push a light into the lights stack.
-void gfx_imm_push_light(ImmRenderer*, Light*);
+void gfx_llr_push_light(LLR*, Light*);
 
 /// Pop the last light from the lights stack.
-void gfx_imm_pop_light(ImmRenderer*);
+void gfx_llr_pop_light(LLR*);
 
 /// Load a skeleton.
 ///
 /// If a skeleton is loaded, subsequent meshes are rendered with joint data
 /// passed to the shader. This has a cost, so if subsequent meshes are not
 /// animated, unload the skeleton prior to rendering them.
-void gfx_imm_set_skeleton(ImmRenderer*, const Anima*, const Skeleton*);
+void gfx_llr_set_skeleton(LLR*, const Anima*, const Skeleton*);
 
 /// Unload the loaded skeleton.
-void gfx_imm_unset_skeleton(ImmRenderer*);
+void gfx_llr_unset_skeleton(LLR*);
 
-/// Render the mesh.
-void gfx_imm_render_mesh(ImmRenderer*, const Mesh*);
-
-// -----------------------------------------------------------------------------
-// Immediate-mode rendering of primitives.
-//
-// This is rather inefficient and should be reserved for debug rendering. It
-// also does not support lighting; the primitives are rendered with a constant
-// colour.
-
-/// Draw a set of triangles.
-void gfx_imm_draw_triangles(ImmRenderer*, const vec3[], size_t num_triangles);
-
-/// Draw a triangle.
-void gfx_imm_draw_triangle(ImmRenderer*, const vec3[3]);
+/// Set the camera.
+void gfx_llr_set_camera(LLR*, const Camera*);
 
-/// Draw a bounding box.
-void gfx_imm_draw_aabb2(ImmRenderer*, aabb2);
+/// Set the view-projection matrix.
+// void gfx_llr_set_view_projection_matrix(LLR*, const mat4*);
 
-/// Draw a bounding box.
-void gfx_imm_draw_aabb3(ImmRenderer*, aabb3);
+/// Render the geometry.
+void gfx_llr_render_geometry(LLR*, const Geometry*);
 
-/// Draw a box.
-///
-/// The vertices must be given in the following order:
-///
-///     7 ----- 6
-///    /       /|
-///   3 ----- 2 |
-///   |       | |
-///   | 4 ----- 5
-///   |/      |/
-///   0 ----- 1
-void gfx_imm_draw_box3(ImmRenderer* renderer, const vec3 vertices[8]);
-
-/// Set the render colour.
-void gfx_imm_set_colour(ImmRenderer*, vec4 colour);
+/// Render the mesh.
+void gfx_llr_render_mesh(LLR*, const Mesh*);
 
 // -----------------------------------------------------------------------------
 // Matrix stack manipulation.
-//
-// Common to both scene and and primitive rendering.
 
 /// Load an identity model matrix. Clears the matrix stack.
-void gfx_imm_load_identity(ImmRenderer* renderer);
+void gfx_llr_load_identity(LLR* renderer);
 
 /// Push the given matrix to the matrix stack.
-void gfx_imm_push_matrix(ImmRenderer* renderer, const mat4* matrix);
+void gfx_llr_push_matrix(LLR* renderer, const mat4* matrix);
 
 /// Pop the top of the matrix stack.
-void gfx_imm_pop_matrix(ImmRenderer* renderer);
+void gfx_llr_pop_matrix(LLR* renderer);
 
 /// Push a translation matrix to the matrix stack.
-void gfx_imm_translate(ImmRenderer* renderer, vec3 offset);
+void gfx_llr_translate(LLR* renderer, vec3 offset);
 
 /// Set the model matrix. Clears the matrix stack.
-void gfx_imm_set_model_matrix(ImmRenderer*, const mat4*);
-
-// -----------------------------------------------------------------------------
-// Camera
-//
-// Common to both scene and and primitive rendering.
-
-/// Set the camera.
-void gfx_imm_set_camera(ImmRenderer*, const Camera*);
-
-/// Set the view-projection matrix.
-// void gfx_imm_set_view_projection_matrix(ImmRenderer*, const mat4*);
+void gfx_llr_set_model_matrix(LLR*, const mat4*);
diff --git a/include/gfx/renderer.h b/include/gfx/renderer.h
index 2a4ada1..1da74eb 100644
--- a/include/gfx/renderer.h
+++ b/include/gfx/renderer.h
@@ -1,23 +1,12 @@
 #pragma once
 
-#include <math/aabb2.h>
-#include <math/aabb3.h>
-#include <math/camera.h>
 #include <math/defs.h>
-#include <math/mat4.h>
-#include <math/vec3.h>
-#include <math/vec4.h>
 
 typedef struct GfxCore     GfxCore;
 typedef struct Scene       Scene;
 typedef struct SceneCamera SceneCamera;
 
-typedef struct ImmRenderer ImmRenderer;
-typedef struct Renderer    Renderer;
-
-// -----------------------------------------------------------------------------
-// Main Renderer.
-// -----------------------------------------------------------------------------
+typedef struct Renderer Renderer;
 
 typedef enum RenderSceneMode {
   RenderDefault,
@@ -38,67 +27,3 @@ void gfx_render_scene(Renderer*, const RenderSceneParams*);
 
 /// Update the scene.
 void gfx_update(Scene*, const SceneCamera*, R t);
-
-// -----------------------------------------------------------------------------
-// Immediate Mode Renderer.
-// -----------------------------------------------------------------------------
-
-/// Prepare the graphics systems for immediate-mode rendering.
-///
-/// Call this before issuing any immediate-mode rendering draws.
-void gfx_imm_start(ImmRenderer*);
-
-/// End immediate mode rendering.
-///
-/// Call this after issuing immediate-mode rendering draws and before swapping
-/// buffers.
-void gfx_imm_end(ImmRenderer*);
-
-/// Draw a set of triangles.
-void gfx_imm_draw_triangles(ImmRenderer*, const vec3[], size_t num_triangles);
-
-/// Draw a triangle.
-void gfx_imm_draw_triangle(ImmRenderer*, const vec3[3]);
-
-/// Draw a bounding box.
-void gfx_imm_draw_aabb2(ImmRenderer*, aabb2);
-
-/// Draw a bounding box.
-void gfx_imm_draw_aabb3(ImmRenderer*, aabb3);
-
-/// Draw a box.
-///
-/// The vertices must be given in the following order:
-///
-///     7 ----- 6
-///    /       /|
-///   3 ----- 2 |
-///   |       | |
-///   | 4 ----- 5
-///   |/      |/
-///   0 ----- 1
-void gfx_imm_draw_box3(ImmRenderer* renderer, const vec3 vertices[8]);
-
-/// Set the camera.
-void gfx_imm_set_camera(ImmRenderer*, const Camera*);
-
-/// Load an identity model matrix. Clears the matrix stack.
-void gfx_imm_load_identity(ImmRenderer* renderer);
-
-/// Push the given matrix to the matrix stack.
-void gfx_imm_push_matrix(ImmRenderer* renderer, const mat4* matrix);
-
-/// Pop the top of the matrix stack.
-void gfx_imm_pop_matrix(ImmRenderer* renderer);
-
-/// Push a translation matrix to the matrix stack.
-void gfx_imm_translate(ImmRenderer* renderer, vec3 offset);
-
-/// Set the model matrix. Clears the matrix stack.
-void gfx_imm_set_model_matrix(ImmRenderer*, const mat4*);
-
-/// Set the view-projection matrix.
-void gfx_imm_set_view_projection_matrix(ImmRenderer*, const mat4*);
-
-/// Set the render colour.
-void gfx_imm_set_colour(ImmRenderer*, vec4 colour);
diff --git a/include/gfx/renderer/imm_renderer.h b/include/gfx/renderer/imm_renderer.h
new file mode 100644
index 0000000..db4d290
--- /dev/null
+++ b/include/gfx/renderer/imm_renderer.h
@@ -0,0 +1,55 @@
+#pragma once
+
+#include <math/aabb2.h>
+#include <math/aabb3.h>
+#include <math/camera.h>
+#include <math/mat4.h>
+#include <math/vec3.h>
+#include <math/vec4.h>
+
+typedef struct ImmRenderer ImmRenderer;
+
+/// Prepare the graphics systems for immediate-mode rendering.
+///
+/// Call this before issuing any immediate-mode rendering draws.
+void gfx_imm_start(ImmRenderer*);
+
+/// End immediate mode rendering.
+///
+/// Call this after issuing immediate-mode rendering draws and before swapping
+/// buffers.
+void gfx_imm_end(ImmRenderer*);
+
+/// Flush draw commands.
+///
+/// This should be done when changing any state that may affect the rendering of
+/// primitives; for example, LLR matrix stack changes.
+void gfx_imm_flush(ImmRenderer*);
+
+/// Draw a set of triangles.
+void gfx_imm_draw_triangles(ImmRenderer*, const vec3[], size_t num_triangles);
+
+/// Draw a triangle.
+void gfx_imm_draw_triangle(ImmRenderer*, const vec3[3]);
+
+/// Draw a bounding box.
+void gfx_imm_draw_aabb2(ImmRenderer*, aabb2);
+
+/// Draw a bounding box.
+void gfx_imm_draw_aabb3(ImmRenderer*, aabb3);
+
+/// Draw a box.
+///
+/// The vertices must be given in the following order:
+///
+///     7 ----- 6
+///    /       /|
+///   3 ----- 2 |
+///   |       | |
+///   | 4 ----- 5
+///   |/      |/
+///   0 ----- 1
+void gfx_imm_draw_box3(ImmRenderer* renderer, const vec3 vertices[8]);
+
+/// Set the render colour.
+void gfx_imm_set_colour(ImmRenderer*, vec4 colour);
diff --git a/include/gfx/scene.h b/include/gfx/scene.h
index abcaa70..37a7e0b 100644
--- a/include/gfx/scene.h
+++ b/include/gfx/scene.h
@@ -1,10 +1,11 @@
 #pragma once
 
+// TODO: Remove references to gfx/llr once the transition is complete.
+#include <gfx/llr/light.h>
+#include <gfx/llr/material.h>
+#include <gfx/llr/mesh.h>
 #include <gfx/scene/animation.h>
 #include <gfx/scene/camera.h>
-#include <gfx/scene/light.h>
-#include <gfx/scene/material.h>
-#include <gfx/scene/mesh.h>
 #include <gfx/scene/model.h>
 #include <gfx/scene/node.h>
 #include <gfx/scene/object.h>
diff --git a/include/gfx/sizes.h b/include/gfx/sizes.h
index 14f72bc..3eb7481 100644
--- a/include/gfx/sizes.h
+++ b/include/gfx/sizes.h
@@ -77,14 +77,20 @@
 /// Maximum number of compiler defines in a Shader.
 #define GFX_MAX_SHADER_COMPILER_DEFINES 16
 
-// Renderer.
+// Low-level renderer.
+
+/// Maximum number of lights that the low-level renderer can enable per rendered
+/// mesh.
+#define GFX_LLR_MAX_NUM_LIGHTS 8
+
+/// Maximum number of matrices in the low-level renderer's matrix stack.
+#define GFX_LLR_MAX_NUM_MATRICES 32
+
+// Immediate-mode Renderer.
 
 /// Maximum number of triangles that the immediate-mode renderer can draw in a
 /// frame.
-#define IMM_MAX_NUM_TRIANGLES 1024
-
-/// Maximum number of matrices in the immediate-mode renderer's matrix stack.
-#define IMM_MAX_NUM_MATRICES 32
+#define GFX_IMM_MAX_NUM_TRIANGLES 1024
 
 // Asset Cache.
 
diff --git a/src/asset/model.c b/src/asset/model.c
index 402b2e1..0c57470 100644
--- a/src/asset/model.c
+++ b/src/asset/model.c
@@ -84,13 +84,12 @@
 #include "asset/texture.h"
 #include "gfx/core.h"
 #include "gfx/gfx.h"
+#include "gfx/llr/material.h"
+#include "gfx/llr/mesh.h"
 #include "gfx/scene/animation.h"
 #include "gfx/scene/camera.h"
-#include "gfx/scene/material.h"
-#include "gfx/scene/mesh.h"
 #include "gfx/scene/node.h"
 #include "gfx/scene/object.h"
-#include "gfx/scene/scene.h"
 #include "gfx/sizes.h"
 #include "gfx/util/shader.h"
 
diff --git a/src/core/core.c b/src/core/core.c
index 90038c6..e1671ea 100644
--- a/src/core/core.c
+++ b/src/core/core.c
@@ -420,6 +420,10 @@ void gfx_destroy_shader_program(GfxCore* gfxcore, ShaderProgram** prog) {
     // Remove the shader program from the cache.
     ProgramCache*            cache = &gfxcore->program_cache;
     ShaderProgramCacheEntry* entry = find_program_cache_entry(cache, *prog);
+    // TODO: The following assertion is too restrictive. Clients can end up
+    //  re-using the same shader by virtue of the cache. The assertion assumes
+    //  that no two "different" clients use the same set of shaders. This can
+    //  be relaxed by reference-counting the shaders in the cache.
     assert(entry); // Must be there, shaders can't go untracked.
     mempool_free(cache, &entry);
 
diff --git a/src/gfx.c b/src/gfx.c
index cd2ac90..4291ae7 100644
--- a/src/gfx.c
+++ b/src/gfx.c
@@ -2,20 +2,20 @@
 
 #include "asset/asset_cache.h"
 #include "core/core_impl.h"
+#include "llr/llr_impl.h"
 #include "renderer/imm_renderer_impl.h"
 #include "renderer/renderer_impl.h"
 #include "scene/scene_memory.h"
 
-#include <log/log.h>
-
 #include <assert.h>
 #include <stdlib.h>
 
 typedef struct Gfx {
   AssetCache  asset_cache;
   GfxCore     gfxcore;
-  Renderer    renderer;
+  LLR         llr;
   ImmRenderer imm_renderer;
+  Renderer    renderer;
 } Gfx;
 
 Gfx* gfx_init(void) {
@@ -24,16 +24,20 @@ Gfx* gfx_init(void) {
     return 0;
   }
   gfx_init_gfxcore(&gfx->gfxcore);
-  if (!renderer_make(&gfx->renderer, &gfx->gfxcore)) {
+  if (!gfx_llr_make(&gfx->llr, &gfx->gfxcore)) {
     gfx_destroy(&gfx);
     return 0;
   }
-  if (!imm_renderer_make(&gfx->imm_renderer, &gfx->gfxcore)) {
+  if (!gfx_imm_make(&gfx->imm_renderer, &gfx->gfxcore, &gfx->llr)) {
     // TODO: Add error logs to the initialization failure cases here and inside
     // the renderers.
     gfx_destroy(&gfx);
     return 0;
   }
+  if (!gfx_renderer_make(&gfx->renderer, &gfx->llr, &gfx->gfxcore)) {
+    gfx_destroy(&gfx);
+    return 0;
+  }
   gfx_init_asset_cache(&gfx->asset_cache);
   scene_mem_init();
   return gfx;
@@ -45,8 +49,9 @@ void gfx_destroy(Gfx** gfx) {
   }
   scene_mem_destroy();
   gfx_destroy_asset_cache(&(*gfx)->asset_cache);
-  renderer_destroy(&(*gfx)->renderer);
-  imm_renderer_destroy(&(*gfx)->imm_renderer);
+  gfx_renderer_destroy(&(*gfx)->renderer);
+  gfx_imm_destroy(&(*gfx)->imm_renderer);
+  gfx_llr_destroy(&(*gfx)->llr);
   gfx_del_gfxcore(&(*gfx)->gfxcore);
   free(*gfx);
   *gfx = 0;
@@ -67,6 +72,11 @@ ImmRenderer* gfx_get_imm_renderer(Gfx* gfx) {
   return &gfx->imm_renderer;
 }
 
+LLR* gfx_get_llr(Gfx* gfx) {
+  assert(gfx);
+  return &gfx->llr;
+}
+
 AssetCache* gfx_get_asset_cache(Gfx* gfx) {
   assert(gfx);
   return &gfx->asset_cache;
diff --git a/src/llr/light.c b/src/llr/light.c
index 168f16a..1d1c40d 100644
--- a/src/llr/light.c
+++ b/src/llr/light.c
@@ -1,4 +1,4 @@
-#include "../scene/light_impl.h"
+#include "light_impl.h"
 
 #include "../scene/node_impl.h"
 #include "../scene/scene_memory.h"
diff --git a/src/llr/llr.c b/src/llr/llr.c
index 62a7c30..746f4b3 100644
--- a/src/llr/llr.c
+++ b/src/llr/llr.c
@@ -1,17 +1,14 @@
-#include "imm_renderer_impl.h"
 #include "light_impl.h"
+#include "llr_impl.h"
 #include "mesh_impl.h"
 
+#include "llr/material_impl.h"
 #include "scene/animation_impl.h"
 
 #include <gfx/core.h>
 #include <gfx/util/ibl.h>
-#include <gfx/util/shader.h>
-
-#include <math/aabb3.h>
 
 #include <cassert.h>
-#include <string.h> // memcpy
 
 static const int IRRADIANCE_MAP_WIDTH               = 1024;
 static const int IRRADIANCE_MAP_HEIGHT              = 1024;
@@ -21,7 +18,7 @@ static const int BRDF_INTEGRATION_MAP_WIDTH         = 512;
 static const int BRDF_INTEGRATION_MAP_HEIGHT        = 512;
 
 /// Initialize renderer state for IBL.
-static bool init_ibl(ImmRenderer* renderer) {
+static bool init_ibl(LLR* renderer) {
   assert(renderer);
   assert(!renderer->ibl);
   assert(!renderer->brdf_integration_map);
@@ -44,8 +41,7 @@ static bool init_ibl(ImmRenderer* renderer) {
 //
 /// Compute irradiance and prefiltered environment maps for the light if they
 /// have not been already computed.
-static bool set_up_environment_light(
-    ImmRenderer* renderer, EnvironmentLight* light) {
+static bool set_up_environment_light(LLR* renderer, EnvironmentLight* light) {
   assert(renderer);
   assert(light);
   assert(renderer->ibl);
@@ -92,7 +88,7 @@ cleanup:
   return false;
 }
 
-static void configure_light(ImmRenderer* renderer, Light* light) {
+static void configure_light(LLR* renderer, Light* light) {
   assert(renderer);
   assert(light);
 
@@ -127,20 +123,35 @@ static void configure_light(ImmRenderer* renderer, Light* light) {
   }
 }
 
-static void configure_state(ImmRenderer* renderer) {
+static void configure_state(LLR* renderer) {
   assert(renderer);
 
   // Check if anything changed first so that we don't call gfx_apply_uniforms()
   // unnecessarily.
-  const bool anything_changed =
-      renderer->camera_changed || renderer->lights_changed ||
-      renderer->skeleton_changed || renderer->shader_changed;
-  if (!anything_changed) {
+  const bool nothing_changed = (renderer->changed_flags == 0);
+  if (nothing_changed) {
+    return;
+  }
+  // Setting a null shader is also allowed, in which case there is nothing to
+  // configure.
+  if (renderer->shader == 0) {
+    renderer->shader_changed = false;
     return;
   }
 
   // For convenience.
   ShaderProgram* const shader = renderer->shader;
+  const mat4* const    model = &renderer->matrix_stack[renderer->stack_pointer];
+
+  // TODO: Check to see which ones the shader actually uses and avoid
+  //  computing the unnecessary matrices.
+
+  if (renderer->matrix_changed || renderer->shader_changed) {
+    renderer->matrix_changed = false;
+
+    gfx_set_mat4_uniform(shader, "Model", model);
+    gfx_set_mat4_uniform(shader, "ModelMatrix", model);
+  }
 
   // TODO: camera_changed is not set anywhere. Need to think how imm primitive
   //  rendering and imm mesh rendering work together. We could treat imm
@@ -150,14 +161,10 @@ static void configure_state(ImmRenderer* renderer) {
 
     // Set all supported camera-related uniforms. Shaders can choose which ones
     // to use.
-    // TODO: Check to see which ones the shader actually uses and avoid
-    //  computing the unnecessary matrices.
-    const mat4* const model = &renderer->matrix_stack[renderer->stack_pointer];
-    const mat4        modelview = mat4_mul(renderer->view, *model);
+    const mat4 modelview = mat4_mul(renderer->view, *model);
     const mat4 view_proj = mat4_mul(renderer->projection, renderer->view);
     const mat4 mvp       = mat4_mul(renderer->projection, modelview);
 
-    gfx_set_mat4_uniform(shader, "ModelMatrix", model);
     gfx_set_mat4_uniform(shader, "Modelview", &modelview);
     gfx_set_mat4_uniform(shader, "View", &renderer->view);
     gfx_set_mat4_uniform(shader, "Projection", &renderer->projection);
@@ -195,58 +202,26 @@ static void configure_state(ImmRenderer* renderer) {
   gfx_apply_uniforms(renderer->shader);
 }
 
-bool gfx_imm_make(ImmRenderer* renderer, GfxCore* gfxcore) {
+bool gfx_llr_make(LLR* renderer, GfxCore* gfxcore) {
   assert(renderer);
   assert(gfxcore);
 
-  const size_t num_triangle_verts = IMM_MAX_NUM_TRIANGLES * 3;
-
   renderer->gfxcore = gfxcore;
-
-  renderer->triangles = gfx_make_geometry(
-      gfxcore,
-      &(GeometryDesc){.type         = Triangles,
-                      .buffer_usage = BufferDynamic,
-                      .num_verts    = num_triangle_verts,
-                      .positions3d  = (BufferView3d){
-                           .size_bytes = num_triangle_verts * sizeof(vec3)}});
-  if (!renderer->triangles) {
-    goto cleanup;
-  }
-
-  renderer->imm_shader = gfx_make_immediate_mode_shader(gfxcore);
-  if (!renderer->imm_shader) {
-    goto cleanup;
-  }
-  renderer->shader = renderer->imm_shader;
-
   if (!init_ibl(renderer)) {
     goto cleanup;
   }
-
-  gfx_imm_load_identity(renderer);
-  gfx_imm_set_colour(renderer, vec4_make(0.0f, 0.0f, 0.0f, 1.0f));
-
+  gfx_llr_load_identity(renderer);
   return true;
 
 cleanup:
-  gfx_imm_destroy(renderer);
+  gfx_llr_destroy(renderer);
   return false;
 }
 
-void gfx_imm_destroy(ImmRenderer* renderer) {
+void gfx_llr_destroy(LLR* renderer) {
   assert(renderer);
   assert(renderer->gfxcore);
 
-  if (renderer->triangles) {
-    gfx_destroy_geometry(renderer->gfxcore, &renderer->triangles);
-    // TODO: Could also destroy the geometry's buffers here.
-  }
-
-  if (renderer->imm_shader) {
-    gfx_destroy_shader_program(renderer->gfxcore, &renderer->imm_shader);
-  }
-
   if (renderer->brdf_integration_map) {
     gfx_destroy_texture(renderer->gfxcore, &renderer->brdf_integration_map);
   }
@@ -257,43 +232,9 @@ void gfx_imm_destroy(ImmRenderer* renderer) {
   }
 }
 
-void gfx_imm_flush(ImmRenderer* renderer) {
-  assert(renderer);
-
-  if (renderer->num_triangle_verts > 0) {
-    configure_state(renderer);
-
-    gfx_update_geometry(
-        renderer->triangles,
-        &(GeometryDesc){
-            .num_verts   = renderer->num_triangle_verts,
-            .positions3d = (BufferView3d){
-                                          .data       = renderer->triangle_verts,
-                                          .size_bytes = renderer->num_triangle_verts * sizeof(vec3)}
-    });
-
-    gfx_apply_uniforms(renderer->shader);
-    gfx_render_geometry(renderer->triangles);
-
-    renderer->num_triangle_verts = 0;
-  }
-}
-
-void gfx_imm_set_shader(ImmRenderer* renderer, ShaderProgram* shader) {
+void gfx_llr_set_shader(LLR* renderer, ShaderProgram* shader) {
   assert(renderer);
-  assert(shader);
-
-  // TODO: It would probably be best to make the imm renderer work in terms of a
-  //  new LLR renderer. Otherwise we need to constantly flush stuff everywhere
-  //  "just in case". This would still allow the imm to render meshes with
-  //  lighting etc. We just need to create an actual Mesh out of the 'triangles'
-  //  Geometry that imm currently has. The change would greatly simplify the
-  //  implementation of this otherwise coupled LLR-IMM renderer.
-  //  Need to decide where to put the matrix stack manipulation. Might be good
-  //  to move to the LLR. (Currently, manipulating the stack causes an imm
-  //  flush, but that's because we have coupled imm with stack manipulation,
-  //  which the new design seems like would address.)
-  gfx_imm_flush(renderer);
+  // null shader is allowed, so do not assert it.
 
   // It's important to not set shader_changed unnecessarily, since that would
   // re-trigger the setting of uniforms.
@@ -303,36 +244,17 @@ void gfx_imm_set_shader(ImmRenderer* renderer, ShaderProgram* shader) {
   }
 }
 
-void gfx_imm_start(ImmRenderer* renderer) {
-  assert(renderer);
-
-  // Shader uniforms are applied lazily.
-  // TODO: In the event that gfx_activate_shader_program() activates uniforms
-  //  automatically for convenience, call an overload here that doesn't do so.
-  gfx_activate_shader_program(renderer->shader);
-}
-
-void gfx_imm_end(ImmRenderer* renderer) {
-  assert(renderer);
-
-  gfx_imm_flush(renderer);
-  gfx_deactivate_shader_program(renderer->shader);
-
-  // TODO: Should we clear all of the render state here as well? At least set
-  //  the 'changed' variables to false, for example.
-}
-
-void gfx_imm_push_light(ImmRenderer* renderer, Light* light) {
+void gfx_llr_push_light(LLR* renderer, Light* light) {
   assert(renderer);
   assert(light);
   assert(renderer->num_lights >= 0);
-  ASSERT(renderer->num_lights < IMM_MAX_NUM_LIGHTS);
+  ASSERT(renderer->num_lights < GFX_LLR_MAX_NUM_LIGHTS);
 
   renderer->lights[renderer->num_lights++] = light;
   renderer->lights_changed                 = true;
 }
 
-void gfx_imm_pop_light(ImmRenderer* renderer) {
+void gfx_llr_pop_light(LLR* renderer) {
   assert(renderer);
   ASSERT(renderer->num_lights > 0);
 
@@ -340,8 +262,8 @@ void gfx_imm_pop_light(ImmRenderer* renderer) {
   renderer->lights_changed                 = true;
 }
 
-void gfx_imm_set_skeleton(
-    ImmRenderer* renderer, const Anima* anima, const Skeleton* skeleton) {
+void gfx_llr_set_skeleton(
+    LLR* renderer, const Anima* anima, const Skeleton* skeleton) {
   assert(renderer);
   assert(anima);
   assert(skeleton);
@@ -356,150 +278,73 @@ void gfx_imm_set_skeleton(
   renderer->skeleton_changed = true;
 }
 
-void gfx_imm_unset_skeleton(ImmRenderer* renderer) {
+void gfx_llr_unset_skeleton(LLR* renderer) {
   assert(renderer);
 
   renderer->num_joints       = 0;
   renderer->skeleton_changed = true;
 }
 
-void gfx_imm_render_mesh(ImmRenderer* renderer, const Mesh* mesh) {
-  assert(renderer);
-  assert(mesh);
-  assert(mesh->geometry);
-  assert(mesh->material);
-
-  configure_state(renderer);
-  gfx_render_geometry(mesh->geometry);
-}
-
-void gfx_imm_draw_triangles(
-    ImmRenderer* renderer, const vec3 verts[], size_t num_triangles) {
+void gfx_llr_set_camera(LLR* renderer, const Camera* camera) {
   assert(renderer);
-  assert(verts);
-  const size_t new_verts = num_triangles * 3;
-  assert(
-      renderer->num_triangle_verts + new_verts < (IMM_MAX_NUM_TRIANGLES * 3));
-
-  memcpy(
-      renderer->triangle_verts + renderer->num_triangle_verts, verts,
-      new_verts * sizeof(vec3));
 
-  renderer->num_triangle_verts += new_verts;
-}
-
-void gfx_imm_draw_triangle(ImmRenderer* renderer, const vec3 verts[3]) {
-  gfx_imm_draw_triangles(renderer, verts, 1);
+  const mat4 view = spatial3_inverse_transform(&camera->spatial);
+  // const mat4 view_proj = mat4_mul(camera->projection, view);
+  // gfx_llr_set_view_projection_matrix(renderer, &view_proj);
+  renderer->view           = view;
+  renderer->projection     = camera->projection;
+  renderer->camera_changed = true;
 }
 
-void gfx_imm_draw_aabb2(ImmRenderer* renderer, aabb2 box) {
-  assert(renderer);
-
-  // clang-format off
-  const vec3 verts[4] = {
-      vec3_make(box.min.x, box.min.y, 0),    // 3 ---- 2
-      vec3_make(box.max.x, box.min.y, 0),    // |      |
-      vec3_make(box.max.x, box.max.y, 0),    // |      |
-      vec3_make(box.min.x, box.max.y, 0)};   // 0 ---- 1
-  // clang-format on
-
-#define tri(i0, i1, i2) verts[i0], verts[i1], verts[i2]
-  const vec3 tris[6] = {tri(0, 1, 2), tri(0, 2, 3)};
-#undef tri
-
-  gfx_imm_draw_triangles(renderer, tris, 2);
-}
+// void gfx_llr_set_view_projection_matrix(
+//     LLR* renderer, const mat4* view_proj) {
+//   assert(renderer);
+//   assert(renderer->shader);
+//
+//   gfx_llr_flush(renderer);
+//   gfx_set_mat4_uniform(renderer->shader, "ViewProjection", view_proj);
+// }
 
-void gfx_imm_draw_aabb3(ImmRenderer* renderer, aabb3 box) {
+void gfx_llr_render_geometry(LLR* renderer, const Geometry* geometry) {
   assert(renderer);
+  assert(geometry);
 
-  // clang-format off
-  const vec3 vertices[8] = {
-      vec3_make(box.min.x, box.min.y, box.max.z), //     7 ----- 6
-      vec3_make(box.max.x, box.min.y, box.max.z), //    /       /|
-      vec3_make(box.max.x, box.max.y, box.max.z), //   3 ----- 2 |
-      vec3_make(box.min.x, box.max.y, box.max.z), //   |       | |
-      vec3_make(box.min.x, box.min.y, box.min.z), //   | 4 ----- 5
-      vec3_make(box.max.x, box.min.y, box.min.z), //   |/      |/
-      vec3_make(box.max.x, box.max.y, box.min.z), //   0 ----- 1
-      vec3_make(box.min.x, box.max.y, box.min.z)};
-  // clang-format on
-
-  gfx_imm_draw_box3(renderer, vertices);
-}
-
-void gfx_imm_draw_box3(ImmRenderer* renderer, const vec3 vertices[8]) {
-  assert(renderer);
-  assert(vertices);
-
-  //     7 ----- 6
-  //    /       /|
-  //   3 ----- 2 |
-  //   |       | |
-  //   | 4 ----- 5
-  //   |/      |/
-  //   0 ----- 1
-
-#define tri(i0, i1, i2) vertices[i0], vertices[i1], vertices[i2]
-  const vec3 tris[36] = {
-      // Front.
-      tri(0, 1, 2), tri(0, 2, 3),
-      // Right.
-      tri(1, 5, 6), tri(1, 6, 2),
-      // Back.
-      tri(5, 4, 7), tri(5, 7, 6),
-      // Left.
-      tri(4, 0, 03), tri(4, 3, 7),
-      // Top.
-      tri(3, 2, 6), tri(3, 6, 7),
-      // Bottom.
-      tri(0, 4, 5), tri(0, 5, 1)};
-
-  gfx_imm_draw_triangles(renderer, tris, 12);
+  configure_state(renderer);
+  gfx_render_geometry(geometry);
 }
 
-void gfx_imm_set_colour(ImmRenderer* renderer, vec4 colour) {
+void gfx_llr_render_mesh(LLR* renderer, const Mesh* mesh) {
   assert(renderer);
   assert(renderer->shader);
+  assert(mesh);
+  assert(mesh->geometry);
+  assert(mesh->material);
 
-  gfx_imm_flush(renderer);
-
-  gfx_set_vec4_uniform(renderer->shader, "Colour", colour);
-}
-
-// Load the top of the matrix stack into the shader.
-static void update_shader_model_matrix(ImmRenderer* renderer) {
-  assert(renderer);
-
-  gfx_imm_flush(renderer);
-
-  gfx_set_mat4_uniform(
-      renderer->shader, "Model",
-      &renderer->matrix_stack[renderer->stack_pointer]);
+  gfx_material_activate(renderer->shader, mesh->material);
+  gfx_llr_render_geometry(renderer, mesh->geometry);
 }
 
-void gfx_imm_load_identity(ImmRenderer* renderer) {
+void gfx_llr_load_identity(LLR* renderer) {
   assert(renderer);
 
   renderer->matrix_stack[0] = mat4_id();
   renderer->stack_pointer   = 0;
-  update_shader_model_matrix(renderer);
+  renderer->matrix_changed  = true;
 }
 
-void gfx_imm_push_matrix(ImmRenderer* renderer, const mat4* matrix) {
+void gfx_llr_push_matrix(LLR* renderer, const mat4* matrix) {
   assert(renderer);
   assert(matrix);
   assert(renderer->stack_pointer >= 0);
-  ASSERT(renderer->stack_pointer < IMM_MAX_NUM_MATRICES);
+  ASSERT(renderer->stack_pointer < GFX_LLR_MAX_NUM_MATRICES);
 
   renderer->stack_pointer += 1;
   renderer->matrix_stack[renderer->stack_pointer] =
       mat4_mul(*matrix, renderer->matrix_stack[renderer->stack_pointer - 1]);
-
-  update_shader_model_matrix(renderer);
+  renderer->matrix_changed = true;
 }
 
-void gfx_imm_pop_matrix(ImmRenderer* renderer) {
+void gfx_llr_pop_matrix(LLR* renderer) {
   assert(renderer);
   ASSERT(renderer->stack_pointer > 0);
 
@@ -508,47 +353,21 @@ void gfx_imm_pop_matrix(ImmRenderer* renderer) {
       &renderer->matrix_stack[renderer->stack_pointer], 0,
       sizeof(renderer->matrix_stack[0]));
   renderer->stack_pointer -= 1;
-
-  update_shader_model_matrix(renderer);
+  renderer->matrix_changed = true;
 }
 
-void gfx_imm_translate(ImmRenderer* renderer, vec3 offset) {
+void gfx_llr_translate(LLR* renderer, vec3 offset) {
   assert(renderer);
 
   const mat4 mat = mat4_translate(offset);
-  gfx_imm_push_matrix(renderer, &mat);
+  gfx_llr_push_matrix(renderer, &mat);
 }
 
-void gfx_imm_set_model_matrix(ImmRenderer* renderer, const mat4* model) {
+void gfx_llr_set_model_matrix(LLR* renderer, const mat4* model) {
   assert(renderer);
   assert(model);
 
-  gfx_imm_flush(renderer);
-
   renderer->matrix_stack[0] = *model;
   renderer->stack_pointer   = 0;
-  update_shader_model_matrix(renderer);
+  renderer->matrix_changed  = true;
 }
-
-void gfx_imm_set_camera(ImmRenderer* renderer, const Camera* camera) {
-  assert(renderer);
-  assert(renderer->shader);
-
-  gfx_imm_flush(renderer);
-
-  const mat4 view = spatial3_inverse_transform(&camera->spatial);
-  // const mat4 view_proj = mat4_mul(camera->projection, view);
-  // gfx_imm_set_view_projection_matrix(renderer, &view_proj);
-  renderer->view           = view;
-  renderer->projection     = camera->projection;
-  renderer->camera_changed = true;
-}
-
-// void gfx_imm_set_view_projection_matrix(
-//     ImmRenderer* renderer, const mat4* view_proj) {
-//   assert(renderer);
-//   assert(renderer->shader);
-//
-//   gfx_imm_flush(renderer);
-//   gfx_set_mat4_uniform(renderer->shader, "ViewProjection", view_proj);
-// }
diff --git a/src/llr/llr_impl.h b/src/llr/llr_impl.h
index 5ccabd1..e9dc0ac 100644
--- a/src/llr/llr_impl.h
+++ b/src/llr/llr_impl.h
@@ -8,6 +8,7 @@
 
 #include <stdbool.h>
 #include <stddef.h>
+#include <stdint.h>
 
 typedef struct Geometry      Geometry;
 typedef struct GfxCore       GfxCore;
@@ -33,67 +34,47 @@ typedef struct Texture       Texture;
 /// Note that the shader program API has its own level of caching as well, so
 /// reconfiguration at the level of the renderer does not result in the
 /// worst-case set of graphics API calls.
-///
-/// Currently, the immediate mode renderer can only draw up to a maximum number
-/// of primitives per frame. It does not adjust this number dynamically. Keeps
-/// things simple while the extra complexity is not needed.
-/// TODO: Flush the buffer when it reaches its maximum size to remove this
-///  constraint.
-typedef struct ImmRenderer {
+typedef struct LLR {
   GfxCore* gfxcore;
 
-  vec3 camera_position;
-  mat4 view;           // Camera view matrix.
-  mat4 projection;     // Camera projection matrix.
-  bool camera_changed; // Whether the camera parameters have changed.
-
-  // -------------------------------------------
-  // Immediate-mode rendering of scene elements.
+  union {
+    struct {
+      bool shader_changed   : 1; // Whether the shader has changed.
+      bool camera_changed   : 1; // Whether the camera parameters have changed.
+      bool lights_changed   : 1; // Whether the lights have changed.
+      bool skeleton_changed : 1; // Whether the skeleton has changed.
+      bool matrix_changed   : 1; // Whether the matrix stack has changed.
+    };
+    uint8_t changed_flags;
+  };
 
   IBL*     ibl;
   Texture* brdf_integration_map;
 
-  ShaderProgram* shader;         // Active shader. Not owned.
-  bool           shader_changed; // Whether the shader has changed.
+  ShaderProgram* shader; // Active shader. Not owned.
+
+  vec3 camera_position;
+  mat4 view;       // Camera view matrix.
+  mat4 projection; // Camera projection matrix.
 
   // Lights are not const because environment lights store lazily-computed
   // irradiance maps.
-  Light* lights[IMM_MAX_NUM_LIGHTS]; // Lights stack.
-  int    num_lights;   // Number of lights enabled at a given point in time. It
-                       // points to one past the top of the stack.
-  bool lights_changed; // Whether the lights have changed.
+  Light* lights[GFX_LLR_MAX_NUM_LIGHTS]; // Lights stack.
+  int    num_lights; // Number of lights enabled at a given point in time. It
+                     // points to one past the top of the stack.
 
-  bool   skeleton_changed;
   size_t num_joints;
   mat4   joint_matrices[GFX_MAX_NUM_JOINTS];
 
-  // ---------------------------------------
-  // Immediate-mode rendering of primitives.
-
-  ShaderProgram* imm_shader; // Immediate-mode shader program for primitives.
-  Geometry*      triangles;
-  size_t         num_triangle_verts; // Number of triangle verts this frame.
-  // TODO: wireframe rendering.
-  struct {
-    bool wireframe : 1;
-  } flags;
-  vec3 triangle_verts[IMM_MAX_NUM_TRIANGLES * 3];
-
-  // -------------
-  // Matrix stack.
-
   // The matrix stack contains pre-multiplied matrices.
   // It is also never empty. The top of the stack is an identity matrix when the
   // stack is "empty" from the user's perspective.
-  mat4 matrix_stack[IMM_MAX_NUM_MATRICES];
+  mat4 matrix_stack[GFX_LLR_MAX_NUM_MATRICES];
   int  stack_pointer; // Points to the top of the stack.
-} ImmRenderer;
+} LLR;
 
 /// Create a new immediate mode renderer.
-bool gfx_imm_make(ImmRenderer*, GfxCore*);
+bool gfx_llr_make(LLR*, GfxCore*);
 
 /// Destroy the immediate mode renderer.
-void gfx_imm_destroy(ImmRenderer*);
-
-/// Flush draw commands.
-void gfx_imm_flush(ImmRenderer*);
+void gfx_llr_destroy(LLR*);
diff --git a/src/llr/material.c b/src/llr/material.c
index 47cb45f..4014482 100644
--- a/src/llr/material.c
+++ b/src/llr/material.c
@@ -48,7 +48,7 @@ static void set_uniform(ShaderProgram* prog, const ShaderUniform* uniform) {
   }
 }
 
-void material_activate(ShaderProgram* shader, const Material* material) {
+void gfx_material_activate(ShaderProgram* shader, const Material* material) {
   assert(material);
   for (int i = 0; i < material->num_uniforms; ++i) {
     const ShaderUniform* uniform = &material->uniforms[i];
diff --git a/src/llr/material_impl.h b/src/llr/material_impl.h
index f27bf4d..138497f 100644
--- a/src/llr/material_impl.h
+++ b/src/llr/material_impl.h
@@ -11,6 +11,5 @@ typedef struct Material {
 
 /// Activate the material.
 ///
-/// This activates the material's shader and configures the shader uniforms that
-/// are specific to the material.
-void material_activate(ShaderProgram* shader, const Material* material);
+/// This configures the shader uniforms that are specific to the material.
+void gfx_material_activate(ShaderProgram* shader, const Material* material);
diff --git a/src/llr/mesh.c b/src/llr/mesh.c
index ae75d8c..3aebb04 100644
--- a/src/llr/mesh.c
+++ b/src/llr/mesh.c
@@ -1,4 +1,4 @@
-#include "../scene/mesh_impl.h"
+#include "mesh_impl.h"
 
 #include "../scene/scene_memory.h"
 
diff --git a/src/renderer/imm_renderer.c b/src/renderer/imm_renderer.c
new file mode 100644
index 0000000..01cc5bb
--- /dev/null
+++ b/src/renderer/imm_renderer.c
@@ -0,0 +1,192 @@
+#include "imm_renderer_impl.h"
+
+#include <gfx/core.h>
+#include <gfx/llr/llr.h>
+#include <gfx/renderer/imm_renderer.h>
+#include <gfx/util/shader.h>
+
+#include <math/aabb3.h>
+
+#include <assert.h>
+#include <string.h> // memcpy
+
+bool gfx_imm_make(ImmRenderer* renderer, GfxCore* gfxcore, LLR* llr) {
+  assert(renderer);
+  assert(gfxcore);
+  assert(llr);
+
+  const size_t num_triangle_verts = GFX_IMM_MAX_NUM_TRIANGLES * 3;
+
+  renderer->gfxcore = gfxcore;
+  renderer->llr     = llr;
+
+  renderer->triangles = gfx_make_geometry(
+      gfxcore,
+      &(GeometryDesc){.type         = Triangles,
+                      .buffer_usage = BufferDynamic,
+                      .num_verts    = num_triangle_verts,
+                      .positions3d  = (BufferView3d){
+                           .size_bytes = num_triangle_verts * sizeof(vec3)}});
+  if (!renderer->triangles) {
+    goto cleanup;
+  }
+
+  renderer->shader = gfx_make_immediate_mode_shader(gfxcore);
+  if (!renderer->shader) {
+    goto cleanup;
+  }
+
+  gfx_imm_set_colour(renderer, vec4_make(0.0f, 0.0f, 0.0f, 1.0f));
+
+  return true;
+
+cleanup:
+  gfx_imm_destroy(renderer);
+  return false;
+}
+
+void gfx_imm_destroy(ImmRenderer* renderer) {
+  assert(renderer);
+  assert(renderer->gfxcore);
+
+  if (renderer->triangles) {
+    gfx_destroy_geometry(renderer->gfxcore, &renderer->triangles);
+    // TODO: Could also destroy the geometry's buffers here.
+  }
+
+  if (renderer->shader) {
+    gfx_destroy_shader_program(renderer->gfxcore, &renderer->shader);
+  }
+}
+
+void gfx_imm_flush(ImmRenderer* renderer) {
+  assert(renderer);
+
+  if (renderer->num_triangle_verts > 0) {
+    gfx_update_geometry(
+        renderer->triangles,
+        &(GeometryDesc){
+            .num_verts   = renderer->num_triangle_verts,
+            .positions3d = (BufferView3d){
+                                          .data       = renderer->triangle_verts,
+                                          .size_bytes = renderer->num_triangle_verts * sizeof(vec3)}
+    });
+
+    gfx_llr_render_geometry(renderer->llr, renderer->triangles);
+
+    renderer->num_triangle_verts = 0;
+  }
+}
+
+void gfx_imm_start(ImmRenderer* renderer) {
+  assert(renderer);
+
+  // Shader uniforms are applied lazily.
+  // TODO: In the event that gfx_activate_shader_program() activates uniforms
+  //  automatically for convenience, call an overload here that doesn't do so.
+  // gfx_activate_shader_program(renderer->shader);
+  gfx_llr_set_shader(renderer->llr, renderer->shader);
+}
+
+void gfx_imm_end(ImmRenderer* renderer) {
+  assert(renderer);
+
+  gfx_imm_flush(renderer);
+  // gfx_deactivate_shader_program(renderer->shader);
+  gfx_llr_set_shader(renderer->llr, 0);
+}
+
+void gfx_imm_draw_triangles(
+    ImmRenderer* renderer, const vec3 verts[], size_t num_triangles) {
+  assert(renderer);
+  assert(verts);
+  const size_t new_verts = num_triangles * 3;
+  assert(
+      renderer->num_triangle_verts + new_verts <
+      (GFX_IMM_MAX_NUM_TRIANGLES * 3));
+
+  memcpy(
+      renderer->triangle_verts + renderer->num_triangle_verts, verts,
+      new_verts * sizeof(vec3));
+
+  renderer->num_triangle_verts += new_verts;
+}
+
+void gfx_imm_draw_triangle(ImmRenderer* renderer, const vec3 verts[3]) {
+  gfx_imm_draw_triangles(renderer, verts, 1);
+}
+
+void gfx_imm_draw_aabb2(ImmRenderer* renderer, aabb2 box) {
+  assert(renderer);
+
+  // clang-format off
+  const vec3 verts[4] = {
+      vec3_make(box.min.x, box.min.y, 0),    // 3 ---- 2
+      vec3_make(box.max.x, box.min.y, 0),    // |      |
+      vec3_make(box.max.x, box.max.y, 0),    // |      |
+      vec3_make(box.min.x, box.max.y, 0)};   // 0 ---- 1
+  // clang-format on
+
+#define tri(i0, i1, i2) verts[i0], verts[i1], verts[i2]
+  const vec3 tris[6] = {tri(0, 1, 2), tri(0, 2, 3)};
+#undef tri
+
+  gfx_imm_draw_triangles(renderer, tris, 2);
+}
+
+void gfx_imm_draw_aabb3(ImmRenderer* renderer, aabb3 box) {
+  assert(renderer);
+
+  // clang-format off
+  const vec3 vertices[8] = {
+      vec3_make(box.min.x, box.min.y, box.max.z), //     7 ----- 6
+      vec3_make(box.max.x, box.min.y, box.max.z), //    /       /|
+      vec3_make(box.max.x, box.max.y, box.max.z), //   3 ----- 2 |
+      vec3_make(box.min.x, box.max.y, box.max.z), //   |       | |
+      vec3_make(box.min.x, box.min.y, box.min.z), //   | 4 ----- 5
+      vec3_make(box.max.x, box.min.y, box.min.z), //   |/      |/
+      vec3_make(box.max.x, box.max.y, box.min.z), //   0 ----- 1
+      vec3_make(box.min.x, box.max.y, box.min.z)};
+  // clang-format on
+
+  gfx_imm_draw_box3(renderer, vertices);
+}
+
+void gfx_imm_draw_box3(ImmRenderer* renderer, const vec3 vertices[8]) {
+  assert(renderer);
+  assert(vertices);
+
+  //     7 ----- 6
+  //    /       /|
+  //   3 ----- 2 |
+  //   |       | |
+  //   | 4 ----- 5
+  //   |/      |/
+  //   0 ----- 1
+
+#define tri(i0, i1, i2) vertices[i0], vertices[i1], vertices[i2]
+  const vec3 tris[36] = {
+      // Front.
+      tri(0, 1, 2), tri(0, 2, 3),
+      // Right.
+      tri(1, 5, 6), tri(1, 6, 2),
+      // Back.
+      tri(5, 4, 7), tri(5, 7, 6),
+      // Left.
+      tri(4, 0, 03), tri(4, 3, 7),
+      // Top.
+      tri(3, 2, 6), tri(3, 6, 7),
+      // Bottom.
+      tri(0, 4, 5), tri(0, 5, 1)};
+
+  gfx_imm_draw_triangles(renderer, tris, 12);
+}
+
+void gfx_imm_set_colour(ImmRenderer* renderer, vec4 colour) {
+  assert(renderer);
+  assert(renderer->shader);
+
+  gfx_imm_flush(renderer);
+
+  gfx_set_vec4_uniform(renderer->shader, "Colour", colour);
+}
diff --git a/src/renderer/imm_renderer_impl.h b/src/renderer/imm_renderer_impl.h
new file mode 100644
index 0000000..61b49a7
--- /dev/null
+++ b/src/renderer/imm_renderer_impl.h
@@ -0,0 +1,43 @@
+#pragma once
+
+#include <gfx/sizes.h>
+
+#include <math/vec3.h>
+
+#include <stdbool.h>
+#include <stddef.h>
+
+typedef struct Geometry      Geometry;
+typedef struct GfxCore       GfxCore;
+typedef struct IBL           IBL;
+typedef struct LLR           LLR;
+typedef struct Material      Material;
+typedef struct ShaderProgram ShaderProgram;
+typedef struct Texture       Texture;
+
+/// Immediate mode renderer.
+///
+/// Currently, the immediate mode renderer can only draw up to a maximum number
+/// of primitives per frame. It does not adjust this number dynamically. Keeps
+/// things simple while the extra complexity is not needed.
+/// TODO: Flush the buffer when it reaches its maximum size to remove this
+///  constraint.
+typedef struct ImmRenderer {
+  GfxCore* gfxcore;
+  LLR*     llr;
+
+  ShaderProgram* shader; // Immediate-mode shader program for primitives.
+  Geometry*      triangles;
+  size_t         num_triangle_verts; // Number of triangle verts this frame.
+  // TODO: wireframe rendering.
+  struct {
+    bool wireframe : 1;
+  } flags;
+  vec3 triangle_verts[GFX_IMM_MAX_NUM_TRIANGLES * 3];
+} ImmRenderer;
+
+/// Create a new immediate mode renderer.
+bool gfx_imm_make(ImmRenderer*, GfxCore*, LLR*);
+
+/// Destroy the immediate mode renderer.
+void gfx_imm_destroy(ImmRenderer*);
diff --git a/src/renderer/renderer.c b/src/renderer/renderer.c
index c2a7dda..0c1fe78 100644
--- a/src/renderer/renderer.c
+++ b/src/renderer/renderer.c
@@ -1,10 +1,10 @@
 #include "renderer_impl.h"
 
+#include "llr/light_impl.h"
+#include "llr/material_impl.h"
+#include "llr/mesh_impl.h"
 #include "scene/animation_impl.h"
 #include "scene/camera_impl.h"
-#include "scene/light_impl.h"
-#include "scene/material_impl.h"
-#include "scene/mesh_impl.h"
 #include "scene/model_impl.h"
 #include "scene/node_impl.h"
 #include "scene/object_impl.h"
@@ -12,16 +12,18 @@
 #include "scene/scene_memory.h"
 
 #include <gfx/core.h>
+#include <gfx/llr/llr.h>
 #include <gfx/util/ibl.h>
 #include <gfx/util/shader.h>
 
-#include <log/log.h>
+// #include <log/log.h>
+#include "gfx/gfx.h"
+
 #include <math/mat4.h>
 #include <math/spatial3.h>
 
 #include <assert.h>
 
-// TODO: Move to a header like "constants.h".
 static const int IRRADIANCE_MAP_WIDTH               = 1024;
 static const int IRRADIANCE_MAP_HEIGHT              = 1024;
 static const int PREFILTERED_ENVIRONMENT_MAP_WIDTH  = 128;
@@ -29,16 +31,18 @@ static const int PREFILTERED_ENVIRONMENT_MAP_HEIGHT = 128;
 static const int BRDF_INTEGRATION_MAP_WIDTH         = 512;
 static const int BRDF_INTEGRATION_MAP_HEIGHT        = 512;
 
-bool renderer_make(Renderer* renderer, GfxCore* gfxcore) {
+bool gfx_renderer_make(Renderer* renderer, LLR* llr, GfxCore* gfxcore) {
   assert(renderer);
+  assert(llr);
   assert(gfxcore);
 
   renderer->gfxcore = gfxcore;
+  renderer->llr     = llr;
 
   return true;
 }
 
-void renderer_destroy(Renderer* renderer) {
+void gfx_renderer_destroy(Renderer* renderer) {
   if (!renderer) {
     return;
   }
@@ -117,9 +121,9 @@ static ShaderProgram* load_shader(Renderer* renderer, RenderSceneMode mode) {
 //   }
 // }
 
-/// Computes irradiance and prefiltered environment maps for the light if they
+/// Compute irradiance and prefiltered environment maps for the light if they
 /// have not been already computed.
-static bool setup_environment_light(
+static bool set_up_environment_light(
     Renderer* renderer, GfxCore* gfxcore, EnvironmentLight* light) {
   assert(renderer);
   assert(light);
@@ -168,6 +172,7 @@ cleanup:
 
 typedef struct RenderState {
   GfxCore*       gfxcore;
+  LLR*           llr;
   Renderer*      renderer;
   ShaderProgram* shader; // Null to use scene shaders.
   const Scene*   scene;
@@ -209,6 +214,7 @@ static void draw_recursively(
 
   // Anima.
   if (node->type == AnimaNode) {
+    // Save the anima so that we can animate objects.
     state->anima = gfx_get_node_anima(node);
   }
   // Activate light.
@@ -217,7 +223,7 @@ static void draw_recursively(
     assert(light);
 
     if (light->type == EnvironmentLightType) {
-      bool result = setup_environment_light(
+      bool result = set_up_environment_light(
           state->renderer, state->gfxcore, &light->environment);
       // TODO: Handle the result in a better way.
       assert(result);
@@ -238,11 +244,13 @@ static void draw_recursively(
     // TODO: Here we would frustum-cull the object.
 
     // TODO: Avoid computing matrices like Modelview or MVP if the shader does
-    // not use them.
+    //  not use them.
     const mat4 model_matrix = node_transform;
     const mat4 modelview    = mat4_mul(*state->view_matrix, model_matrix);
     const mat4 mvp          = mat4_mul(*state->projection, modelview);
 
+    // A model/anima can have many skeletons. We need to animate the given
+    // object using its skeleton, not just any skeleton of the anima.
     if (object->skeleton.val) {
       load_skeleton(state, object->skeleton);
     }
@@ -260,9 +268,11 @@ static void draw_recursively(
       assert(mesh->material);
 
       // TODO: Here we would frustum-cull the mesh. The AABB would have to be
-      // transformed by the model matrix. Rotation would make the AABB
-      // relatively large, but still, the culling would be conservative.
+      //  transformed by the model matrix. Rotation would make the AABB
+      //  relatively large, but still, the culling would be conservative.
 
+      // TODO: Make sure we strictly set only the uniforms that are required by
+      //  mesh rendering. See the other item below.
       // Apply common shader uniforms not captured by materials.
       ShaderProgram* shader = state->shader ? state->shader : mesh->shader;
       gfx_set_mat4_uniform(shader, "ModelMatrix", &model_matrix);
@@ -270,7 +280,10 @@ static void draw_recursively(
       gfx_set_mat4_uniform(shader, "View", state->view_matrix);
       gfx_set_mat4_uniform(shader, "Projection", state->projection);
       gfx_set_mat4_uniform(shader, "MVP", &mvp);
+      // TODO: CameraRotation is only used by the skyquad and cubemap_filtering
+      //  shaders, not mesh rendering.
       gfx_set_mat4_uniform(shader, "CameraRotation", state->camera_rotation);
+      // TODO: Fovy and Aspect are only used by the skyquad, not necessary here.
       gfx_set_float_uniform(shader, "Fovy", state->fovy);
       gfx_set_float_uniform(shader, "Aspect", state->aspect);
       if (state->camera) {
@@ -297,9 +310,9 @@ static void draw_recursively(
             shader, "PrefilteredEnvironmentMap",
             light->prefiltered_environment_map);
         gfx_set_float_uniform(
-            shader, "MaxReflectionLOD", light->max_reflection_lod);
+            shader, "MaxReflectionLOD", (float)light->max_reflection_lod);
       }
-      material_activate(shader, mesh->material);
+      gfx_material_activate(shader, mesh->material);
       gfx_activate_shader_program(shader);
       gfx_apply_uniforms(shader);
       gfx_render_geometry(mesh->geometry);
@@ -327,7 +340,7 @@ void gfx_render_scene(Renderer* renderer, const RenderSceneParams* params) {
   const Scene*       scene  = params->scene;
   const SceneCamera* camera = params->camera;
 
-  GfxCore* gfxcore = renderer->gfxcore;
+  GfxCore* const gfxcore = renderer->gfxcore;
 
   mat4 projection, camera_rotation, view_matrix;
   if (camera) {
@@ -347,6 +360,7 @@ void gfx_render_scene(Renderer* renderer, const RenderSceneParams* params) {
 
   RenderState state = {
       .gfxcore           = gfxcore,
+      .llr               = renderer->llr,
       .renderer          = renderer,
       .shader            = shader,
       .scene             = scene,
diff --git a/src/renderer/renderer_impl.h b/src/renderer/renderer_impl.h
index fc14dcb..6fd0c15 100644
--- a/src/renderer/renderer_impl.h
+++ b/src/renderer/renderer_impl.h
@@ -5,11 +5,13 @@
 #include <stdbool.h>
 
 typedef struct IBL           IBL;
+typedef struct LLR           LLR;
 typedef struct ShaderProgram ShaderProgram;
 typedef struct Texture       Texture;
 
 typedef struct Renderer {
   GfxCore* gfxcore;
+  LLR*     llr;
   IBL*     ibl;
   Texture* brdf_integration_map;
   struct {
@@ -21,7 +23,7 @@ typedef struct Renderer {
 } Renderer;
 
 /// Create a new renderer.
-bool renderer_make(Renderer*, GfxCore*);
+bool gfx_renderer_make(Renderer*, LLR*, GfxCore*);
 
 /// Destroy the renderer.
-void renderer_destroy(Renderer*);
+void gfx_renderer_destroy(Renderer*);
diff --git a/src/scene/node.c b/src/scene/node.c
index 67ce93c..e359f73 100644
--- a/src/scene/node.c
+++ b/src/scene/node.c
@@ -2,7 +2,7 @@
 
 #include "animation_impl.h"
 #include "camera_impl.h"
-#include "light_impl.h"
+#include "llr/light_impl.h"
 #include "model_impl.h"
 #include "object_impl.h"
 #include "scene_graph.h"
diff --git a/src/scene/object.c b/src/scene/object.c
index e8e3ee6..27ff5db 100644
--- a/src/scene/object.c
+++ b/src/scene/object.c
@@ -2,7 +2,7 @@
 
 #include <gfx/core.h>
 
-#include "mesh_impl.h"
+#include "llr/mesh_impl.h"
 #include "node_impl.h"
 #include "scene_memory.h"
 
diff --git a/src/scene/object_impl.h b/src/scene/object_impl.h
index ead93f1..e864e53 100644
--- a/src/scene/object_impl.h
+++ b/src/scene/object_impl.h
@@ -4,8 +4,6 @@
 
 #include "types.h"
 
-#include <math/mat4.h>
-
 typedef struct MeshLink {
   mesh_idx      mesh;
   mesh_link_idx next; // Next MeshLink in the list.
diff --git a/src/scene/scene_memory.c b/src/scene/scene_memory.c
index 91880bb..3a01325 100644
--- a/src/scene/scene_memory.c
+++ b/src/scene/scene_memory.c
@@ -4,9 +4,9 @@
 
 #include "animation_impl.h"
 #include "camera_impl.h"
-#include "light_impl.h"
-#include "material_impl.h"
-#include "mesh_impl.h"
+#include "llr/light_impl.h"
+#include "llr/material_impl.h"
+#include "llr/mesh_impl.h"
 #include "model_impl.h"
 #include "node_impl.h"
 #include "object_impl.h"
diff --git a/src/util/skyquad.c b/src/util/skyquad.c
index 08fa044..094de67 100644
--- a/src/util/skyquad.c
+++ b/src/util/skyquad.c
@@ -1,18 +1,14 @@
 #include <gfx/util/skyquad.h>
 
 #include <gfx/core.h>
-#include <gfx/gfx.h>
-#include <gfx/scene/light.h>
-#include <gfx/scene/material.h>
-#include <gfx/scene/mesh.h>
+#include <gfx/llr/light.h>
+#include <gfx/llr/material.h>
+#include <gfx/llr/mesh.h>
 #include <gfx/scene/node.h>
 #include <gfx/scene/object.h>
-#include <gfx/scene/scene.h>
 #include <gfx/util/geometry.h>
 #include <gfx/util/shader.h>
 
-#include <math/vec4.h>
-
 #include <assert.h>
 
 SceneObject* gfx_make_skyquad(GfxCore* gfxcore, const Texture* texture) {
@@ -36,10 +32,9 @@ SceneObject* gfx_make_skyquad(GfxCore* gfxcore, const Texture* texture) {
   }
 
   MaterialDesc material_desc = (MaterialDesc){0};
-  material_desc.uniforms[0]  = (ShaderUniform){
-       .type          = UniformTexture,
-       .value.texture = texture,
-       .name          = sstring_make("Skyquad")};
+  material_desc.uniforms[0]  = (ShaderUniform){.type          = UniformTexture,
+                                               .value.texture = texture,
+                                               .name = sstring_make("Skyquad")};
   material_desc.num_uniforms = 1;
   material                   = gfx_make_material(&material_desc);
   if (!material) {