6 files changed, 1070 insertions, 0 deletions

diff --git a/src/render/imm.c b/src/render/imm.c
new file mode 100644
index 0000000..7ab8d62
--- /dev/null
+++ b/src/render/imm.c
@@ -0,0 +1,194 @@
+#include "imm_impl.h"
+
+#include <gfx/core.h>
+#include <gfx/render/imm.h>
+#include <gfx/render/llr.h>
+#include <gfx/util/shader.h>
+
+#include <math/aabb3.h>
+
+#include <assert.h>
+#include <string.h> // memcpy
+
+bool gfx_imm_make(Imm* 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),
+                                                  .count      = num_triangle_verts}
+  });
+  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(Imm* 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(Imm* 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(Imm* 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(Imm* 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(
+    Imm* 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(Imm* renderer, const vec3 verts[3]) {
+  gfx_imm_draw_triangles(renderer, verts, 1);
+}
+
+void gfx_imm_draw_aabb2(Imm* 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(Imm* 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(Imm* 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(Imm* renderer, vec4 colour) {
+  assert(renderer);
+  assert(renderer->shader);
+
+  gfx_imm_flush(renderer);
+
+  gfx_set_vec4_uniform(renderer->shader, "Colour", colour);
+}
diff --git a/src/render/imm_impl.h b/src/render/imm_impl.h
new file mode 100644
index 0000000..d87b910
--- /dev/null
+++ b/src/render/imm_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 Imm {
+  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];
+} Imm;
+
+/// Create a new immediate mode renderer.
+bool gfx_imm_make(Imm*, GfxCore*, LLR*);
+
+/// Destroy the immediate mode renderer.
+void gfx_imm_destroy(Imm*);
diff --git a/src/render/llr.c b/src/render/llr.c
new file mode 100644
index 0000000..752b65b
--- /dev/null
+++ b/src/render/llr.c
@@ -0,0 +1,441 @@
+#include "llr_impl.h"
+
+#include "animation_impl.h"
+#include "scene/light_impl.h"
+#include "scene/material_impl.h"
+#include "scene/mesh_impl.h"
+#include "scene/node_impl.h"
+
+#include <gfx/core.h>
+#include <gfx/util/ibl.h>
+
+#include <cassert.h>
+
+static const int IRRADIANCE_MAP_WIDTH               = 1024;
+static const int IRRADIANCE_MAP_HEIGHT              = 1024;
+static const int PREFILTERED_ENVIRONMENT_MAP_WIDTH  = 128;
+static const int PREFILTERED_ENVIRONMENT_MAP_HEIGHT = 128;
+static const int BRDF_INTEGRATION_MAP_WIDTH         = 512;
+static const int BRDF_INTEGRATION_MAP_HEIGHT        = 512;
+
+/// Activate the material.
+///
+/// This configures the shader uniforms that are specific to the material.
+static void material_activate(ShaderProgram* shader, const Material* material) {
+  assert(material);
+  for (int i = 0; i < material->num_uniforms; ++i) {
+    const ShaderUniform* uniform = &material->uniforms[i];
+    gfx_set_uniform(shader, uniform);
+  }
+  if (material->alpha_mode != Opaque) {
+    gfx_set_uniform(
+        shader, &(ShaderUniform){.name              = sstring_make("AlphaMode"),
+                                 .type              = UniformInt,
+                                 .value.uniform_int = material->alpha_mode});
+  }
+  if (material->alpha_mode == Mask) {
+    gfx_set_uniform(
+        shader,
+        &(ShaderUniform){.name                = sstring_make("AlphaCutoff"),
+                         .type                = UniformFloat,
+                         .value.uniform_float = material->alpha_cutoff});
+  }
+}
+
+/// Initialize renderer state for IBL.
+static bool init_ibl(LLR* renderer) {
+  assert(renderer);
+  assert(!renderer->ibl);
+  assert(!renderer->brdf_integration_map);
+
+  if (!((renderer->ibl = gfx_make_ibl(renderer->gfxcore)))) {
+    return false;
+  }
+
+  if (!((renderer->brdf_integration_map = gfx_make_brdf_integration_map(
+             renderer->ibl, renderer->gfxcore, BRDF_INTEGRATION_MAP_WIDTH,
+             BRDF_INTEGRATION_MAP_HEIGHT)))) {
+    return false;
+  }
+
+  return true;
+}
+
+/// Compute irradiance and prefiltered environment maps for the light if they
+/// have not been already computed.
+///
+/// This is done lazily here, and not when the light is created, because we
+/// need an IBL instance to do this and it is more convenient for the public
+/// API to create lights without worrying about those details. It also makes the
+/// public API cheaper, since the maps are only computed when they are actually
+/// needed.
+static bool set_up_environment_light(LLR* renderer, EnvironmentLight* light) {
+  assert(renderer);
+  assert(light);
+  assert(renderer->ibl);
+  assert(renderer->brdf_integration_map);
+
+  if (light->irradiance_map) {
+    assert(light->prefiltered_environment_map);
+    return true;
+  }
+
+  // For convenience.
+  GfxCore* gfxcore = renderer->gfxcore;
+
+  Texture* irradiance_map              = 0;
+  Texture* prefiltered_environment_map = 0;
+
+  if (!((irradiance_map = gfx_make_irradiance_map(
+             renderer->ibl, gfxcore, light->environment_map,
+             IRRADIANCE_MAP_WIDTH, IRRADIANCE_MAP_HEIGHT)))) {
+    goto cleanup;
+  }
+
+  int max_mip_level = 0;
+  if (!((prefiltered_environment_map = gfx_make_prefiltered_environment_map(
+             renderer->ibl, gfxcore, light->environment_map,
+             PREFILTERED_ENVIRONMENT_MAP_WIDTH,
+             PREFILTERED_ENVIRONMENT_MAP_HEIGHT, &max_mip_level)))) {
+    goto cleanup;
+  }
+
+  light->irradiance_map              = irradiance_map;
+  light->prefiltered_environment_map = prefiltered_environment_map;
+  light->max_reflection_lod          = max_mip_level;
+
+  return true;
+
+cleanup:
+  if (irradiance_map) {
+    gfx_destroy_texture(gfxcore, &irradiance_map);
+  }
+  if (prefiltered_environment_map) {
+    gfx_destroy_texture(gfxcore, &prefiltered_environment_map);
+  }
+  return false;
+}
+
+static void configure_light(LLR* renderer, Light* light) {
+  assert(renderer);
+  assert(light);
+
+  // For convenience.
+  ShaderProgram* const shader = renderer->shader;
+
+  switch (light->type) {
+  case EnvironmentLightType: {
+    EnvironmentLight* env = &light->environment;
+
+    const bool initialized = set_up_environment_light(renderer, env);
+    ASSERT(initialized);
+    assert(env->environment_map);
+    assert(env->irradiance_map);
+    assert(env->prefiltered_environment_map);
+    assert(renderer->brdf_integration_map);
+
+    gfx_set_texture_uniform(
+        shader, "BRDFIntegrationMap", renderer->brdf_integration_map);
+    gfx_set_texture_uniform(shader, "Sky", env->environment_map);
+    gfx_set_texture_uniform(shader, "IrradianceMap", env->irradiance_map);
+    gfx_set_texture_uniform(
+        shader, "PrefilteredEnvironmentMap", env->prefiltered_environment_map);
+    gfx_set_float_uniform(
+        shader, "MaxReflectionLOD", (float)env->max_reflection_lod);
+
+    break;
+  }
+  default:
+    assert(false); // TODO: Implement other light types.
+    break;
+  }
+}
+
+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 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
+  //  primitive calls like setting a new shader.
+  if (renderer->camera_changed || renderer->shader_changed) {
+    renderer->camera_changed = false;
+
+    // Set all supported camera-related uniforms. Shaders can choose which ones
+    // to use.
+    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, "Modelview", &modelview);
+    gfx_set_mat4_uniform(shader, "View", &renderer->view);
+    gfx_set_mat4_uniform(shader, "Projection", &renderer->projection);
+    gfx_set_mat4_uniform(shader, "ViewProjection", &view_proj);
+    gfx_set_mat4_uniform(shader, "MVP", &mvp);
+    gfx_set_vec3_uniform(shader, "CameraPosition", renderer->camera_position);
+    gfx_set_mat4_uniform(shader, "CameraRotation", &renderer->camera_rotation);
+    gfx_set_float_uniform(shader, "Fovy", renderer->fovy);
+    gfx_set_float_uniform(shader, "Aspect", renderer->aspect);
+  }
+
+  if (renderer->lights_changed || renderer->shader_changed) {
+    renderer->lights_changed = false;
+
+    // TODO: Could do better by only setting the lights that have actually
+    //  changed.
+    // TODO: Will also need to pass the number of lights to the shader once the
+    //  other light types are implemented.
+    for (int i = 0; i < renderer->num_lights; ++i) {
+      configure_light(renderer, renderer->lights[i]);
+    }
+  }
+
+  if (renderer->skeleton_changed || renderer->shader_changed) {
+    renderer->skeleton_changed = false;
+
+    if (renderer->num_joints > 0) {
+      gfx_set_mat4_array_uniform(
+          shader, "JointMatrices", renderer->joint_matrices,
+          renderer->num_joints);
+    }
+  }
+
+  if (renderer->material_changed || renderer->shader_changed) {
+    renderer->material_changed = false;
+
+    // Geometry may be rendered without a material.
+    if (renderer->material) {
+      material_activate(renderer->shader, renderer->material);
+    }
+  }
+
+  if (renderer->shader_changed) {
+    renderer->shader_changed = false;
+    gfx_activate_shader_program(renderer->shader);
+  }
+
+  // TODO: At present, this results in many redundant calls to
+  //  glGetUniformLocation() and glUniformXyz(). Look at the trace.
+  //
+  // TODO: Could add to qapitrace functionality to detect redundant calls and
+  //  other inefficiencies. Maybe ask in the Github first if there would be
+  //  interest in this.
+  //
+  // Must be called after activating the program.
+  gfx_apply_uniforms(renderer->shader);
+}
+
+bool gfx_llr_make(LLR* renderer, GfxCore* gfxcore) {
+  assert(renderer);
+  assert(gfxcore);
+
+  renderer->gfxcore = gfxcore;
+  if (!init_ibl(renderer)) {
+    goto cleanup;
+  }
+  gfx_llr_load_identity(renderer);
+  renderer->view            = mat4_id();
+  renderer->projection      = mat4_id();
+  renderer->camera_rotation = mat4_id();
+  return true;
+
+cleanup:
+  gfx_llr_destroy(renderer);
+  return false;
+}
+
+void gfx_llr_destroy(LLR* renderer) {
+  assert(renderer);
+  assert(renderer->gfxcore);
+
+  if (renderer->brdf_integration_map) {
+    gfx_destroy_texture(renderer->gfxcore, &renderer->brdf_integration_map);
+  }
+
+  // TODO: Do this once the IBL from the scene renderer is gone.
+  if (renderer->ibl) {
+    // gfx_destroy_ibl(renderer->gfxcore, &renderer->ibl);
+  }
+}
+
+void gfx_llr_set_shader(LLR* renderer, ShaderProgram* shader) {
+  assert(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.
+  if (renderer->shader != shader) {
+    renderer->shader         = shader;
+    renderer->shader_changed = true;
+  }
+}
+
+void gfx_llr_push_light(LLR* renderer, Light* light) {
+  assert(renderer);
+  assert(light);
+  assert(renderer->num_lights >= 0);
+  ASSERT(renderer->num_lights < GFX_LLR_MAX_NUM_LIGHTS);
+
+  renderer->lights[renderer->num_lights++] = light;
+  renderer->lights_changed                 = true;
+}
+
+void gfx_llr_pop_light(LLR* renderer) {
+  assert(renderer);
+  ASSERT(renderer->num_lights > 0);
+
+  renderer->lights[--renderer->num_lights] = 0;
+  renderer->lights_changed                 = true;
+}
+
+void gfx_llr_set_skeleton(
+    LLR* renderer, const Anima* anima, const Skeleton* skeleton) {
+  assert(renderer);
+  assert(anima);
+  assert(skeleton);
+  assert(skeleton->num_joints <= GFX_MAX_NUM_JOINTS);
+
+  for (size_t i = 0; i < skeleton->num_joints; ++i) {
+    const joint_idx joint_index = skeleton->joints[i];
+    const Joint*    joint       = &anima->joints[joint_index];
+    renderer->joint_matrices[i] = joint->joint_matrix;
+  }
+  renderer->num_joints       = skeleton->num_joints;
+  renderer->skeleton_changed = true;
+}
+
+void gfx_llr_clear_skeleton(LLR* renderer) {
+  assert(renderer);
+
+  renderer->num_joints       = 0;
+  renderer->skeleton_changed = true;
+}
+
+void gfx_llr_set_material(LLR* renderer, const Material* material) {
+  assert(renderer);
+  assert(material);
+
+  renderer->material         = material;
+  renderer->material_changed = true;
+}
+
+void gfx_llr_set_camera(LLR* renderer, const Camera* camera) {
+  assert(renderer);
+
+  renderer->camera_position = camera->spatial.p;
+  renderer->camera_rotation =
+      mat4_rotation(spatial3_transform(&camera->spatial));
+  renderer->view       = spatial3_inverse_transform(&camera->spatial);
+  renderer->projection = camera->projection;
+  // Assuming a perspective matrix.
+  renderer->fovy = (R)atan(1.0 / (mat4_at(camera->projection, 1, 1))) * 2;
+  renderer->camera_changed = true;
+}
+
+void gfx_llr_set_projection_matrix(LLR* renderer, const mat4* projection) {
+  assert(renderer);
+
+  renderer->projection     = *projection;
+  renderer->camera_changed = true;
+}
+
+void gfx_llr_set_aspect(LLR* renderer, float aspect) {
+  assert(renderer);
+
+  renderer->aspect         = aspect;
+  renderer->camera_changed = true;
+}
+
+void gfx_llr_render_geometry(LLR* renderer, const Geometry* geometry) {
+  assert(renderer);
+  assert(geometry);
+
+  configure_state(renderer);
+  gfx_render_geometry(geometry);
+}
+
+void gfx_llr_render_mesh(LLR* renderer, const Mesh* mesh) {
+  assert(renderer);
+  assert(mesh);
+  assert(mesh->geometry);
+  assert(mesh->material);
+  assert(mesh->shader);
+
+  gfx_llr_set_material(renderer, mesh->material);
+  gfx_llr_set_shader(renderer, mesh->shader);
+  gfx_llr_render_geometry(renderer, mesh->geometry);
+}
+
+void gfx_llr_load_identity(LLR* renderer) {
+  assert(renderer);
+
+  renderer->matrix_stack[0] = mat4_id();
+  renderer->stack_pointer   = 0;
+  renderer->matrix_changed  = true;
+}
+
+void gfx_llr_push_matrix(LLR* renderer, const mat4* matrix) {
+  assert(renderer);
+  assert(matrix);
+  assert(renderer->stack_pointer >= 0);
+  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]);
+  renderer->matrix_changed = true;
+}
+
+void gfx_llr_pop_matrix(LLR* renderer) {
+  assert(renderer);
+  ASSERT(renderer->stack_pointer > 0);
+
+  // For debugging, zero out the matrix stack as matrices are popped out.
+  memset(
+      &renderer->matrix_stack[renderer->stack_pointer], 0,
+      sizeof(renderer->matrix_stack[0]));
+  renderer->stack_pointer -= 1;
+  renderer->matrix_changed = true;
+}
+
+void gfx_llr_translate(LLR* renderer, vec3 offset) {
+  assert(renderer);
+
+  const mat4 mat = mat4_translate(offset);
+  gfx_llr_push_matrix(renderer, &mat);
+}
+
+void gfx_llr_set_model_matrix(LLR* renderer, const mat4* model) {
+  assert(renderer);
+  assert(model);
+
+  renderer->matrix_stack[0] = *model;
+  renderer->stack_pointer   = 0;
+  renderer->matrix_changed  = true;
+}
diff --git a/src/render/llr_impl.h b/src/render/llr_impl.h
new file mode 100644
index 0000000..9d70843
--- /dev/null
+++ b/src/render/llr_impl.h
@@ -0,0 +1,85 @@
+#pragma once
+
+#include <gfx/render/llr.h>
+#include <gfx/sizes.h>
+
+#include <math/mat4.h>
+#include <math/vec3.h>
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+typedef struct GfxCore       GfxCore;
+typedef struct IBL           IBL;
+typedef struct Material      Material;
+typedef struct ShaderProgram ShaderProgram;
+typedef struct Texture       Texture;
+
+/// Immediate mode renderer.
+///
+/// The renderer caches state changes in memory and only programs the underlying
+/// shader program when a draw call is issued and if anything has changed. This
+/// keeps the number of graphics API calls to a minimum, but requires tracking
+/// state changes. The 'changed' booleans below fulfill this purpose, and
+/// indicate whether a given state has changed since the last draw call.
+///
+/// The renderer must combine state changes accordingly. For example, if only
+/// the lights have changed, then it is sufficient to update light uniforms in
+/// the current shader program. On the other hand, if the shader program has
+/// changed, then the renderer must reconfigure it from scratch and set light
+/// uniforms, camera uniforms, etc.
+///
+/// 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.
+typedef struct LLR {
+  GfxCore* gfxcore;
+
+  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 material_changed : 1; // Whether the material 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.
+
+  const Material* material; // Active material. Not owned.
+
+  vec3 camera_position;
+  mat4 camera_rotation;
+  mat4 view;       // Camera view matrix.
+  mat4 projection; // Camera projection matrix.
+  R    fovy;       // Camera vertical field of view.
+  R    aspect;     // Aspect ratio.
+
+  // Lights are not const because environment lights store lazily-computed
+  // irradiance maps.
+  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.
+
+  size_t num_joints;
+  mat4   joint_matrices[GFX_MAX_NUM_JOINTS];
+
+  // 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[GFX_LLR_MAX_NUM_MATRICES];
+  int  stack_pointer; // Points to the top of the stack.
+} LLR;
+
+/// Create a new immediate mode renderer.
+bool gfx_llr_make(LLR*, GfxCore*);
+
+/// Destroy the immediate mode renderer.
+void gfx_llr_destroy(LLR*);
diff --git a/src/render/renderer.c b/src/render/renderer.c
new file mode 100644
index 0000000..a9d9bef
--- /dev/null
+++ b/src/render/renderer.c
@@ -0,0 +1,282 @@
+#include "renderer_impl.h"
+
+#include "animation_impl.h"
+#include "llr_impl.h"
+#include "memory.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"
+
+#include <gfx/core.h>
+#include <gfx/render/llr.h>
+#include <gfx/util/shader.h>
+
+#include <math/mat4.h>
+
+#include <assert.h>
+
+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 gfx_renderer_destroy(Renderer* renderer) {
+  if (!renderer) {
+    return;
+  }
+  assert(renderer->gfxcore);
+  GfxCore* gfxcore = renderer->gfxcore;
+  if (renderer->shaders.debug) {
+    gfx_destroy_shader_program(gfxcore, &renderer->shaders.debug);
+  }
+  if (renderer->shaders.normals) {
+    gfx_destroy_shader_program(gfxcore, &renderer->shaders.normals);
+  }
+  if (renderer->shaders.normal_mapped_normals) {
+    gfx_destroy_shader_program(
+        gfxcore, &renderer->shaders.normal_mapped_normals);
+  }
+  if (renderer->shaders.tangents) {
+    gfx_destroy_shader_program(gfxcore, &renderer->shaders.tangents);
+  }
+}
+
+static ShaderProgram* load_shader(Renderer* renderer, RenderSceneMode mode) {
+  assert(renderer);
+
+#define LOAD_AND_RETURN(pShader, constructor)   \
+  {                                             \
+    if (!pShader) {                             \
+      pShader = constructor(renderer->gfxcore); \
+    }                                           \
+    assert(pShader);                            \
+    return pShader;                             \
+  }
+
+  switch (mode) {
+  case RenderDefault:
+    return 0;
+  case RenderDebug:
+    LOAD_AND_RETURN(renderer->shaders.debug, gfx_make_debug3d_shader);
+  case RenderNormals:
+    LOAD_AND_RETURN(renderer->shaders.normals, gfx_make_view_normals_shader);
+  case RenderNormalMappedNormals:
+    LOAD_AND_RETURN(
+        renderer->shaders.normal_mapped_normals,
+        gfx_make_view_normal_mapped_normals_shader);
+  case RenderTangents:
+    LOAD_AND_RETURN(renderer->shaders.tangents, gfx_make_view_tangents_shader);
+  }
+  assert(false);
+  return 0;
+}
+
+// static void log_matrix(const mat4* m) {
+//   for (int row = 0; row < 4; ++row) {
+//     LOGI("[ %5.2f, %5.2f, %5.2f, %5.2f ]", m->val[0][row], m->val[1][row],
+//          m->val[2][row], m->val[3][row]);
+//   }
+// }
+
+typedef struct RenderState {
+  GfxCore*          gfxcore;
+  LLR*              llr;
+  Renderer*         renderer;
+  ShaderProgram*    shader; // Null to use scene shaders.
+  const Scene*      scene;
+  const Anima*      anima;
+  RenderSceneFilter filter;
+} RenderState;
+
+static void draw_children(
+    RenderState* state, const mat4* node_transform, const SceneNode* node);
+
+/// Draw the scene recursively.
+static void draw_recursively(
+    RenderState* state, mat4 parent_transform, const SceneNode* node) {
+  assert(state);
+  const mat4 node_transform = mat4_mul(parent_transform, node->transform);
+
+  // Anima.
+  if (node->type == AnimaNode) {
+    // Save the anima so that we can animate objects.
+    state->anima = gfx_get_node_anima(node);
+
+    draw_children(state, &node_transform, node);
+  }
+  // Activate light.
+  else if (node->type == LightNode) {
+    Light* light = mem_get_light(node->light);
+    assert(light);
+    gfx_llr_push_light(state->llr, light);
+    {
+      draw_children(state, &node_transform, node);
+    }
+    gfx_llr_pop_light(state->llr);
+  }
+  // Model.
+  else if (node->type == ModelNode) {
+    const Model*     model = gfx_get_node_model(node);
+    const SceneNode* root  = mem_get_node(model->root);
+    draw_recursively(state, parent_transform, root);
+    draw_children(state, &node_transform, node);
+  }
+  // Render object.
+  else if (node->type == ObjectNode) {
+    const SceneObject* object = mem_get_object(node->object);
+    assert(object);
+
+    // TODO: Here we would frustum-cull the object.
+
+    // 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) {
+      const Skeleton* skeleton = mem_get_skeleton(object->skeleton);
+      gfx_llr_set_skeleton(state->llr, state->anima, skeleton);
+    }
+
+    const mat4 model_matrix = node_transform;
+
+    for (mesh_link_idx mesh_link_index = object->mesh_link;
+         mesh_link_index.val;) {
+      const MeshLink* mesh_link = mem_get_mesh_link(mesh_link_index);
+      mesh_link_index           = mesh_link->next;
+
+      const Mesh* mesh = mem_get_mesh(mesh_link->mesh);
+      if (!mesh) {
+        continue;
+      }
+
+      // Filter out by material.
+      const Material* material = mesh->material;
+      if (material) {
+        const AlphaMode mode = material->alpha_mode;
+        switch (state->filter) {
+        case RenderOpaqueAndAlphaMasked:
+          if (mode == Blend) {
+            continue;
+          }
+          break;
+        case RenderTransparent:
+          if (mode != Blend) {
+            continue;
+          }
+          break;
+        }
+      }
+
+      // 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.
+
+      ShaderProgram* shader = state->shader ? state->shader : mesh->shader;
+      gfx_llr_set_shader(state->llr, shader);
+      gfx_llr_set_model_matrix(state->llr, &model_matrix);
+      gfx_llr_render_mesh(state->llr, mesh);
+    }
+
+    if (object->skeleton.val) {
+      gfx_llr_clear_skeleton(state->llr);
+    }
+
+    draw_children(state, &node_transform, node);
+  } else {
+    draw_children(state, &node_transform, node);
+  }
+}
+
+/// Draw the node's children.
+static void draw_children(
+    RenderState* state, const mat4* node_transform, const SceneNode* node) {
+  // Render children recursively.
+  for (node_idx child_index = node->child; child_index.val;) {
+    const SceneNode* child = mem_get_node(child_index);
+    draw_recursively(state, *node_transform, child);
+    child_index = child->next;
+  }
+}
+
+void gfx_render_scene(Renderer* renderer, const RenderSceneParams* params) {
+  assert(renderer);
+  assert(params);
+  assert(params->scene);
+
+  ShaderProgram* const shader = load_shader(renderer, params->mode);
+
+  const Scene*   scene   = params->scene;
+  const Camera*  camera  = params->camera;
+  GfxCore* const gfxcore = renderer->gfxcore;
+
+  int x, y, width, height;
+  gfx_get_viewport(gfxcore, &x, &y, &width, &height);
+  const R aspect = (R)width / (R)height;
+
+  RenderState state = {
+      .gfxcore  = gfxcore,
+      .llr      = renderer->llr,
+      .renderer = renderer,
+      .shader   = shader,
+      .scene    = scene};
+
+  gfx_llr_set_camera(renderer->llr, camera);
+  gfx_llr_set_aspect(renderer->llr, aspect);
+  // TODO: Render Opaque and Mask alpha-mode materials first, then Blend ones.
+  // TODO: I'm not sure if this belongs to the scene renderer per se, or if it
+  //  is something that should be driven from the outside. Specifically, the
+  //  caller could pass in a filter that determines what objects to render. The
+  //  filter could include alpha mode.
+  //  This caller would be some component that understands render passes and
+  //  potentially renders the scene multiple times as needed. For example, a
+  //  depth-prepass, followed by G-buffer, followed by some post-processing,
+  //  etc. Rename this renderer to scene_renderer?
+  // TODO: When rendering transparent geometry, we need to turn off depth
+  //  writes.
+  // Opaque.
+  state.filter = RenderOpaqueAndAlphaMasked;
+  draw_recursively(&state, mat4_id(), gfx_get_scene_root(scene));
+  // Transparent.
+  state.filter = RenderTransparent;
+  draw_recursively(&state, mat4_id(), gfx_get_scene_root(scene));
+}
+
+static void update_rec(SceneNode* node, const Camera* camera, R t) {
+  assert(node);
+  assert(camera);
+
+  const NodeType node_type = gfx_get_node_type(node);
+
+  // TODO: Models do not need to be animated if they are not visible to the
+  //  camera.
+  if (node_type == AnimaNode) {
+    Anima* anima = gfx_get_node_anima_mut(node);
+    gfx_update_animation(anima, (R)t);
+  } else if (node_type == ModelNode) {
+    Model*     model = gfx_get_node_model_mut(node);
+    SceneNode* root  = gfx_get_model_root_mut(model);
+    update_rec(root, camera, t);
+  }
+
+  // Children.
+  SceneNode* child = gfx_get_node_child_mut(node);
+  while (child) {
+    update_rec(child, camera, t);
+    child = gfx_get_node_sibling_mut(child);
+  }
+}
+
+// TODO: Move this outside the renderer.
+void gfx_update(Scene* scene, const Camera* camera, R t) {
+  assert(scene);
+  assert(camera);
+
+  SceneNode* node = gfx_get_scene_root_mut(scene);
+  update_rec(node, camera, t);
+}
diff --git a/src/render/renderer_impl.h b/src/render/renderer_impl.h
new file mode 100644
index 0000000..160ff52
--- /dev/null
+++ b/src/render/renderer_impl.h
@@ -0,0 +1,25 @@
+#pragma once
+
+#include <gfx/render/renderer.h>
+
+#include <stdbool.h>
+
+typedef struct LLR           LLR;
+typedef struct ShaderProgram ShaderProgram;
+
+typedef struct Renderer {
+  GfxCore* gfxcore;
+  LLR*     llr;
+  struct {
+    ShaderProgram* debug;
+    ShaderProgram* normals;
+    ShaderProgram* normal_mapped_normals;
+    ShaderProgram* tangents;
+  } shaders;
+} Renderer;
+
+/// Create a new renderer.
+bool gfx_renderer_make(Renderer*, LLR*, GfxCore*);
+
+/// Destroy the renderer.
+void gfx_renderer_destroy(Renderer*);