1 files changed, 328 insertions, 0 deletions

diff --git a/src/util/ibl.c b/src/util/ibl.c
new file mode 100644
index 0000000..5a79990
--- /dev/null
+++ b/src/util/ibl.c
@@ -0,0 +1,328 @@
+#include <gfx/util/ibl.h>
+
+#include <gfx/core.h>
+#include <gfx/util/geometry.h>
+#include <gfx/util/shader.h>
+#include <math/mat4.h>
+
+#include <assert.h>
+#include <stdlib.h>
+
+typedef struct IBL {
+  Geometry*      quad;
+  ShaderProgram* brdf_integration_map_shader;
+  ShaderProgram* irradiance_map_shader;
+  ShaderProgram* prefiltered_environment_map_shader;
+  Texture*       brdf_integration_map;
+  FrameBuffer*   framebuffer;
+  mat4           rotations[6];
+} IBL;
+
+static const CubemapFace faces[6] = {
+    CubemapFacePosX, // Right.
+    CubemapFaceNegX, // Left.
+    CubemapFacePosY, // Up.
+    CubemapFaceNegY, // Down.
+    CubemapFacePosZ, // Back.
+    CubemapFaceNegZ, // Front.
+};
+
+static const float flips[6] = {
+    -1.0f, // Right.
+    -1.0f, // Left.
+    +1.0f, // Up.
+    +1.0f, // Down.
+    -1.0f, // Back.
+    -1.0f, // Front.
+};
+
+IBL* gfx_make_ibl(GfxCore* gfxcore) {
+  assert(gfxcore);
+
+  IBL* ibl = calloc(1, sizeof(IBL));
+  if (!ibl) {
+    return 0;
+  }
+
+  if (!(ibl->quad = gfx_make_quad_11(gfxcore))) {
+    goto cleanup;
+  }
+
+  // We only need the BRDF integration once since we are caching the map, but
+  // compiling the shader up front may lead to fewer surprises. Not that the
+  // shader is fully compiled up front anyway, since the driver will typically
+  // defer full compilation to the first draw call.
+  if (!(ibl->brdf_integration_map_shader =
+            gfx_make_brdf_integration_map_shader(gfxcore))) {
+    goto cleanup;
+  }
+
+  if (!(ibl->irradiance_map_shader = gfx_make_irradiance_map_shader(gfxcore))) {
+    goto cleanup;
+  }
+
+  if (!(ibl->prefiltered_environment_map_shader =
+            gfx_make_prefiltered_environment_map_shader(gfxcore))) {
+    goto cleanup;
+  }
+
+  // Create an empty framebuffer for now. Will attach the colour buffer later
+  // as we render the faces of the cube.
+  if (!(ibl->framebuffer = gfx_make_framebuffer(
+            gfxcore,
+            &(FrameBufferDesc){
+                .colour =
+                    (FrameBufferAttachment){.type = FrameBufferNoAttachment},
+                .depth = (FrameBufferAttachment){
+                    .type = FrameBufferNoAttachment}}))) {
+    goto cleanup;
+  }
+
+  // TODO: Debug the camera rotations. Irradiance debug output should appear
+  // just like the input cubemap.
+
+  // Right.
+  ibl->rotations[0] = mat4_lookat(
+      /*position=*/vec3_make(0, 0, 0),
+      /*target=*/vec3_make(1, 0, 0),
+      /*up=*/vec3_make(0, 1, 0));
+  // Left.
+  ibl->rotations[1] = mat4_lookat(
+      /*position=*/vec3_make(0, 0, 0),
+      /*target=*/vec3_make(-1, 0, 0),
+      /*up=*/vec3_make(0, 1, 0));
+  // Up.
+  ibl->rotations[2] = mat4_lookat(
+      /*position=*/vec3_make(0, 0, 0),
+      /*target=*/vec3_make(0, 1, 0),
+      /*up=*/vec3_make(0, 0, 1));
+  // Down.
+  ibl->rotations[3] = mat4_lookat(
+      /*position=*/vec3_make(0, 0, 0),
+      /*target=*/vec3_make(0, -1, 0),
+      /*up=*/vec3_make(0, 0, -1));
+  // Back.
+  ibl->rotations[4] = mat4_lookat(
+      /*position=*/vec3_make(0, 0, 0),
+      /*target=*/vec3_make(0, 0, 1),
+      /*up=*/vec3_make(0, 1, 0));
+  // Front.
+  ibl->rotations[5] = mat4_lookat(
+      /*position=*/vec3_make(0, 0, 0),
+      /*target=*/vec3_make(0, 0, -1),
+      /*up=*/vec3_make(0, 1, 0));
+
+  return ibl;
+
+cleanup:
+  gfx_destroy_ibl(gfxcore, &ibl);
+  return 0;
+}
+
+void gfx_destroy_ibl(GfxCore* gfxcore, IBL** ibl) {
+  if (!ibl) {
+    return;
+  }
+  if ((*ibl)->quad) {
+    gfx_destroy_geometry(gfxcore, &(*ibl)->quad);
+  }
+  if ((*ibl)->brdf_integration_map_shader) {
+    gfx_destroy_shader_program(gfxcore, &(*ibl)->brdf_integration_map_shader);
+  }
+  if ((*ibl)->irradiance_map_shader) {
+    gfx_destroy_shader_program(gfxcore, &(*ibl)->irradiance_map_shader);
+  }
+  if ((*ibl)->prefiltered_environment_map_shader) {
+    gfx_destroy_shader_program(
+        gfxcore, &(*ibl)->prefiltered_environment_map_shader);
+  }
+  if ((*ibl)->brdf_integration_map) {
+    gfx_destroy_texture(gfxcore, &(*ibl)->brdf_integration_map);
+  }
+  if ((*ibl)->framebuffer) {
+    gfx_destroy_framebuffer(gfxcore, &(*ibl)->framebuffer);
+  }
+  free(*ibl);
+  *ibl = 0;
+}
+
+Texture* gfx_make_brdf_integration_map(
+    IBL* ibl, GfxCore* gfxcore, int width, int height) {
+  assert(ibl);
+  assert(gfxcore);
+
+  if (ibl->brdf_integration_map) {
+    return ibl->brdf_integration_map;
+  }
+
+  bool success = false;
+
+  if (!(ibl->brdf_integration_map = gfx_make_texture(
+            gfxcore, &(TextureDesc){
+                         .width     = width,
+                         .height    = height,
+                         .depth     = 1,
+                         .dimension = Texture2D,
+                         .format    = TextureRG16F,
+                         .filtering = LinearFiltering,
+                         .wrap      = ClampToEdge,
+                         .mipmaps   = false}))) {
+    goto cleanup;
+  }
+
+  gfx_activate_framebuffer(ibl->framebuffer);
+  gfx_framebuffer_set_viewport(ibl->framebuffer, 0, 0, width, height);
+  gfx_activate_shader_program(ibl->brdf_integration_map_shader);
+  if (!gfx_framebuffer_attach_colour(
+          ibl->framebuffer, &(FrameBufferAttachment){
+                                .type              = FrameBufferTexture,
+                                .texture.texture   = ibl->brdf_integration_map,
+                                .texture.mip_level = 0})) {
+    goto cleanup;
+  }
+  gfx_render_geometry(ibl->quad);
+
+  success = true;
+
+cleanup:
+  gfx_deactivate_shader_program(ibl->brdf_integration_map_shader);
+  gfx_deactivate_framebuffer(ibl->framebuffer);
+  if (!success && ibl->brdf_integration_map) {
+    gfx_destroy_texture(gfxcore, &ibl->brdf_integration_map);
+    return 0;
+  } else {
+    return ibl->brdf_integration_map;
+  }
+}
+
+Texture* gfx_make_irradiance_map(
+    IBL* ibl, GfxCore* gfxcore, const Texture* environment_map, int width,
+    int height) {
+  assert(ibl);
+  assert(gfxcore);
+  assert(environment_map);
+
+  bool success = false;
+
+  Texture* irradiance_map = 0;
+
+  // TODO: Could define colour-renderable texture formats separately to make
+  // framebuffer creation less error-prone. Or, at the very least, validate the
+  // choice at runtime.
+  //
+  // Make sure to use a float colour format to avoid [0,1] clamping when the
+  // irradiance values are computed!
+  if (!(irradiance_map = gfx_make_texture(
+            gfxcore, &(TextureDesc){
+                         .width     = width,
+                         .height    = height,
+                         .depth     = 1,
+                         .dimension = TextureCubeMap,
+                         .format    = TextureR11G11B10F,
+                         .filtering = LinearFiltering,
+                         .mipmaps   = false}))) {
+    goto cleanup;
+  }
+
+  gfx_activate_framebuffer(ibl->framebuffer);
+  gfx_framebuffer_set_viewport(ibl->framebuffer, 0, 0, width, height);
+  gfx_activate_shader_program(ibl->irradiance_map_shader);
+  gfx_set_texture_uniform(ibl->irradiance_map_shader, "Sky", environment_map);
+  for (int i = 0; i < 6; ++i) {
+    if (!gfx_framebuffer_attach_colour(
+            ibl->framebuffer, &(FrameBufferAttachment){
+                                  .type            = FrameBufferCubemapTexture,
+                                  .cubemap.face    = faces[i],
+                                  .cubemap.texture = irradiance_map})) {
+      goto cleanup;
+    }
+    gfx_set_float_uniform(ibl->irradiance_map_shader, "Flip", flips[i]);
+    gfx_set_mat4_uniform(
+        ibl->irradiance_map_shader, "CameraRotation", &ibl->rotations[i]);
+    gfx_apply_uniforms(ibl->irradiance_map_shader);
+    gfx_render_geometry(ibl->quad);
+  }
+
+  success = true;
+
+cleanup:
+  gfx_deactivate_shader_program(ibl->irradiance_map_shader);
+  gfx_deactivate_framebuffer(ibl->framebuffer);
+  if (!success && irradiance_map) {
+    gfx_destroy_texture(gfxcore, &irradiance_map);
+    return 0;
+  } else {
+    return irradiance_map;
+  }
+}
+
+Texture* gfx_make_prefiltered_environment_map(
+    IBL* ibl, GfxCore* gfxcore, const Texture* environment_map, int width,
+    int height, int* max_mip_level) {
+  assert(ibl);
+  assert(gfxcore);
+  assert(environment_map);
+  assert(max_mip_level);
+
+  bool success = false;
+
+  Texture* prefiltered_env_map = 0;
+
+  if (!(prefiltered_env_map = gfx_make_texture(
+            gfxcore, &(TextureDesc){
+                         .width     = width,
+                         .height    = height,
+                         .depth     = 1,
+                         .dimension = TextureCubeMap,
+                         .format    = TextureR11G11B10F,
+                         .filtering = LinearFiltering,
+                         .mipmaps   = true}))) {
+    goto cleanup;
+  }
+
+  gfx_activate_framebuffer(ibl->framebuffer);
+  gfx_activate_shader_program(ibl->prefiltered_environment_map_shader);
+  gfx_set_texture_uniform(
+      ibl->prefiltered_environment_map_shader, "Sky", environment_map);
+  const int max_mip = (int)(rlog2(min(width, height)));
+  for (int mip = 0; mip <= max_mip; ++mip) {
+    const int   mip_width  = width >> mip;
+    const int   mip_height = height >> mip;
+    const float roughness  = (float)mip / (float)(max_mip);
+    gfx_framebuffer_set_viewport(ibl->framebuffer, 0, 0, mip_width, mip_height);
+    gfx_set_float_uniform(
+        ibl->prefiltered_environment_map_shader, "Roughness", roughness);
+
+    for (int i = 0; i < 6; ++i) {
+      if (!gfx_framebuffer_attach_colour(
+              ibl->framebuffer, &(FrameBufferAttachment){
+                                    .type         = FrameBufferCubemapTexture,
+                                    .cubemap.face = faces[i],
+                                    .cubemap.mip_level = mip,
+                                    .cubemap.texture = prefiltered_env_map})) {
+        goto cleanup;
+      }
+      gfx_set_float_uniform(
+          ibl->prefiltered_environment_map_shader, "Flip", flips[i]);
+      gfx_set_mat4_uniform(
+          ibl->prefiltered_environment_map_shader, "CameraRotation",
+          &ibl->rotations[i]);
+      gfx_apply_uniforms(ibl->prefiltered_environment_map_shader);
+      gfx_render_geometry(ibl->quad);
+    }
+  }
+
+  *max_mip_level = max_mip;
+
+  success = true;
+
+cleanup:
+  gfx_deactivate_shader_program(ibl->prefiltered_environment_map_shader);
+  gfx_deactivate_framebuffer(ibl->framebuffer);
+  if (!success && prefiltered_env_map) {
+    gfx_destroy_texture(gfxcore, &prefiltered_env_map);
+    return 0;
+  } else {
+    return prefiltered_env_map;
+  }
+}