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

2 files changed, 65 insertions, 3 deletions

diff --git a/source/blender/nodes/shader/CMakeLists.txt b/source/blender/nodes/shader/CMakeLists.txt
index 7885ad78225..e78bf55d840 100644
--- a/source/blender/nodes/shader/CMakeLists.txt
+++ b/source/blender/nodes/shader/CMakeLists.txt
@@ -150,6 +150,22 @@ if(WITH_FREESTYLE)
   add_definitions(-DWITH_FREESTYLE)
 endif()
 
+if(WITH_TBB)
+  add_definitions(-DWITH_TBB)
+  if(WIN32)
+    # TBB includes Windows.h which will define min/max macros
+    # that will collide with the stl versions.
+    add_definitions(-DNOMINMAX)
+  endif()
+  list(APPEND INC_SYS
+    ${TBB_INCLUDE_DIRS}
+  )
+
+  list(APPEND LIB
+    ${TBB_LIBRARIES}
+  )
+endif()
+
 blender_add_lib(bf_nodes_shader "${SRC}" "${INC}" "${INC_SYS}" "${LIB}")
 
 if(WITH_UNITY_BUILD)
diff --git a/source/blender/nodes/shader/nodes/node_shader_tex_sky.cc b/source/blender/nodes/shader/nodes/node_shader_tex_sky.cc
index f5a4d087dbd..97b7f2616ae 100644
--- a/source/blender/nodes/shader/nodes/node_shader_tex_sky.cc
+++ b/source/blender/nodes/shader/nodes/node_shader_tex_sky.cc
@@ -4,6 +4,8 @@
 #include "node_shader_util.hh"
 #include "sky_model.h"
 
+#include "BLI_task.hh"
+
 #include "BKE_context.h"
 #include "BKE_scene.h"
 
@@ -36,7 +38,7 @@ static void node_shader_buts_tex_sky(uiLayout *layout, bContext *C, PointerRNA *
   if (RNA_enum_get(ptr, "sky_type") == SHD_SKY_NISHITA) {
     Scene *scene = CTX_data_scene(C);
     if (BKE_scene_uses_blender_eevee(scene)) {
-      uiItemL(layout, TIP_("Nishita not available in Eevee"), ICON_ERROR);
+      uiItemL(layout, TIP_("Sun disc not available in Eevee"), ICON_ERROR);
     }
     uiItemR(layout, ptr, "sun_disc", UI_ITEM_R_SPLIT_EMPTY_NAME, nullptr, 0);
 
@@ -179,7 +181,7 @@ static int node_shader_gpu_tex_sky(GPUMaterial *mat,
                           GPU_uniform(xyz_to_rgb.g),
                           GPU_uniform(xyz_to_rgb.b));
   }
-  if (tex->sky_model == 1) {
+  else if (tex->sky_model == 1) {
     /* Hosek / Wilkie */
     sun_angles[0] = fmin(M_PI_2, sun_angles[0]); /* clamp to horizon */
     SKY_ArHosekSkyModelState *sky_state = SKY_arhosek_xyz_skymodelstate_alloc_init(
@@ -219,8 +221,52 @@ static int node_shader_gpu_tex_sky(GPUMaterial *mat,
                           GPU_uniform(xyz_to_rgb.g),
                           GPU_uniform(xyz_to_rgb.b));
   }
+  else {
+    /* Nishita */
+
+    Array<float> pixels(4 * GPU_SKY_WIDTH * GPU_SKY_HEIGHT);
+
+    threading::parallel_for(IndexRange(GPU_SKY_HEIGHT), 2, [&](IndexRange range) {
+      SKY_nishita_skymodel_precompute_texture(pixels.data(),
+                                              4,
+                                              range.first(),
+                                              range.one_after_last(),
+                                              GPU_SKY_WIDTH,
+                                              GPU_SKY_HEIGHT,
+                                              tex->sun_elevation,
+                                              tex->altitude,
+                                              tex->air_density,
+                                              tex->dust_density,
+                                              tex->ozone_density);
+    });
+
+    float sun_rotation = fmodf(tex->sun_rotation, 2.0f * M_PI);
+    if (sun_rotation < 0.0f) {
+      sun_rotation += 2.0f * M_PI;
+    }
+    sun_rotation = 2.0f * M_PI - sun_rotation;
+
+    XYZ_to_RGB xyz_to_rgb;
+    get_XYZ_to_RGB_for_gpu(&xyz_to_rgb);
 
-  return GPU_stack_link(mat, node, "node_tex_sky_nishita", in, out);
+    eGPUSamplerState sampler = GPU_SAMPLER_REPEAT | GPU_SAMPLER_FILTER;
+    /* To fix pole issue we clamp the v coordinate. */
+    sampler &= ~GPU_SAMPLER_REPEAT_T;
+    float layer;
+    GPUNodeLink *sky_texture = GPU_image_sky(
+        mat, GPU_SKY_WIDTH, GPU_SKY_HEIGHT, pixels.data(), &layer, sampler);
+    return GPU_stack_link(mat,
+                          node,
+                          "node_tex_sky_nishita",
+                          in,
+                          out,
+                          GPU_constant(&sun_rotation),
+                          GPU_uniform(xyz_to_rgb.r),
+                          GPU_uniform(xyz_to_rgb.g),
+                          GPU_uniform(xyz_to_rgb.b),
+                          sky_texture,
+                          GPU_constant(&layer));
+  }
 }
 
 static void node_shader_update_sky(bNodeTree *ntree, bNode *node)