Eevee: Add support for Nishita sky texture

Sun Disc is currently not supported because it'll need special handling - on the one hand, I'm not sure if Eevee would handle a 1e6 coming out of a background shader without issues, and on the other hand it won't actually cast sharp shadows anyways.
I guess we'd want to internally add a sun to the lamps if Sun Disc is enabled, but getting that right is tricky since the user could e.g. swap RGB channels in the node tree and the lamp wouldn't match that.
Anyways, that can be handled later, the sky itself is already a start.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D13522

1 files changed, 61 insertions, 0 deletions

diff --git a/source/blender/gpu/intern/gpu_material.c b/source/blender/gpu/intern/gpu_material.c
index 75066b21e7b..96809db1587 100644
--- a/source/blender/gpu/intern/gpu_material.c
+++ b/source/blender/gpu/intern/gpu_material.c
@@ -41,12 +41,18 @@
 
 /* Structs */
 #define MAX_COLOR_BAND 128
+#define MAX_GPU_SKIES 8
 
 typedef struct GPUColorBandBuilder {
   float pixels[MAX_COLOR_BAND][CM_TABLE + 1][4];
   int current_layer;
 } GPUColorBandBuilder;
 
+typedef struct GPUSkyBuilder {
+  float pixels[MAX_GPU_SKIES][GPU_SKY_WIDTH * GPU_SKY_HEIGHT][4];
+  int current_layer;
+} GPUSkyBuilder;
+
 struct GPUMaterial {
   /* Contains GPUShader and source code for deferred compilation.
    * Can be shared between similar material (i.e: sharing same nodetree topology). */
@@ -73,6 +79,10 @@ struct GPUMaterial {
   GPUTexture *coba_tex;
   /** Builder for coba_tex. */
   GPUColorBandBuilder *coba_builder;
+  /** 2D Texture array containing all sky textures. */
+  GPUTexture *sky_tex;
+  /** Builder for sky_tex. */
+  GPUSkyBuilder *sky_builder;
   /* Low level node graph(s). Also contains resources needed by the material. */
   GPUNodeGraph graph;
 
@@ -98,6 +108,35 @@ struct GPUMaterial {
 
 /* Functions */
 
+GPUTexture **gpu_material_sky_texture_layer_set(
+    GPUMaterial *mat, int width, int height, const float *pixels, float *row)
+{
+  /* In order to put all sky textures into one 2D array texture,
+   * we need them to be the same size. */
+  BLI_assert(width == GPU_SKY_WIDTH);
+  BLI_assert(height == GPU_SKY_HEIGHT);
+  UNUSED_VARS_NDEBUG(width, height);
+
+  if (mat->sky_builder == NULL) {
+    mat->sky_builder = MEM_mallocN(sizeof(GPUSkyBuilder), "GPUSkyBuilder");
+    mat->sky_builder->current_layer = 0;
+  }
+
+  int layer = mat->sky_builder->current_layer;
+  *row = (float)layer;
+
+  if (*row == MAX_GPU_SKIES) {
+    printf("Too many sky textures in shader!\n");
+  }
+  else {
+    float *dst = (float *)mat->sky_builder->pixels[layer];
+    memcpy(dst, pixels, sizeof(float) * GPU_SKY_WIDTH * GPU_SKY_HEIGHT * 4);
+    mat->sky_builder->current_layer += 1;
+  }
+
+  return &mat->sky_tex;
+}
+
 GPUTexture **gpu_material_ramp_texture_row_set(GPUMaterial *mat,
                                                int size,
                                                float *pixels,
@@ -143,6 +182,24 @@ static void gpu_material_ramp_texture_build(GPUMaterial *mat)
   mat->coba_builder = NULL;
 }
 
+static void gpu_material_sky_texture_build(GPUMaterial *mat)
+{
+  if (mat->sky_builder == NULL) {
+    return;
+  }
+
+  mat->sky_tex = GPU_texture_create_2d_array("mat_sky",
+                                             GPU_SKY_WIDTH,
+                                             GPU_SKY_HEIGHT,
+                                             mat->sky_builder->current_layer,
+                                             1,
+                                             GPU_RGBA32F,
+                                             (float *)mat->sky_builder->pixels);
+
+  MEM_freeN(mat->sky_builder);
+  mat->sky_builder = NULL;
+}
+
 void GPU_material_free_single(GPUMaterial *material)
 {
   bool do_free = atomic_sub_and_fetch_uint32(&material->refcount, 1) == 0;
@@ -161,6 +218,9 @@ void GPU_material_free_single(GPUMaterial *material)
   if (material->coba_tex != NULL) {
     GPU_texture_free(material->coba_tex);
   }
+  if (material->sky_tex != NULL) {
+    GPU_texture_free(material->sky_tex);
+  }
   if (material->sss_profile != NULL) {
     GPU_uniformbuf_free(material->sss_profile);
   }
@@ -684,6 +744,7 @@ GPUMaterial *GPU_material_from_nodetree(Scene *scene,
   ntreeGPUMaterialNodes(localtree, mat);
 
   gpu_material_ramp_texture_build(mat);
+  gpu_material_sky_texture_build(mat);
 
   {
     /* Create source code and search pass cache for an already compiled version. */