1 files changed, 57 insertions, 0 deletions
diff --git a/source/blender/draw/engines/eevee_next/shaders/eevee_light_culling_sort_comp.glsl b/source/blender/draw/engines/eevee_next/shaders/eevee_light_culling_sort_comp.glsl
new file mode 100644
index 00000000000..e98b170cd4c
--- /dev/null
+++ b/source/blender/draw/engines/eevee_next/shaders/eevee_light_culling_sort_comp.glsl
@@ -0,0 +1,57 @@
+
+/**
+ * Sort the lights by their Z distance to the camera.
+ * Outputs ordered light buffer.
+ * One thread processes one Light entity.
+ */
+
+#pragma BLENDER_REQUIRE(common_math_lib.glsl)
+
+shared float zdists_cache[gl_WorkGroupSize.x];
+
+void main()
+{
+  uint src_index = gl_GlobalInvocationID.x;
+  bool valid_thread = true;
+
+  if (src_index >= light_cull_buf.visible_count) {
+    /* Do not return because we use barriers later on (which need uniform control flow).
+     * Just process the same last item but avoid insertion. */
+    src_index = light_cull_buf.visible_count - 1;
+    valid_thread = false;
+  }
+
+  float local_zdist = in_zdist_buf[src_index];
+
+  int prefix_sum = 0;
+  /* Iterate over the whole key buffer. */
+  uint iter = divide_ceil(light_cull_buf.visible_count, gl_WorkGroupSize.x);
+  for (uint i = 0u; i < iter; i++) {
+    uint index = gl_WorkGroupSize.x * i + gl_LocalInvocationID.x;
+    /* NOTE: This will load duplicated values, but they will be discarded. */
+    index = min(index, light_cull_buf.visible_count - 1);
+    zdists_cache[gl_LocalInvocationID.x] = in_zdist_buf[index];
+
+    barrier();
+
+    /* Iterate over the cache line. */
+    uint line_end = min(gl_WorkGroupSize.x, light_cull_buf.visible_count - gl_WorkGroupSize.x * i);
+    for (uint j = 0u; j < line_end; j++) {
+      if (zdists_cache[j] < local_zdist) {
+        prefix_sum++;
+      }
+      else if (zdists_cache[j] == local_zdist) {
+        /* Same depth, use index to order and avoid same prefix for 2 different lights. */
+        if ((gl_WorkGroupSize.x * i + j) < src_index) {
+          prefix_sum++;
+        }
+      }
+    }
+  }
+
+  if (valid_thread) {
+    /* Copy sorted light to render light buffer. */
+    uint input_index = in_key_buf[src_index];
+    out_light_buf[prefix_sum] = in_light_buf[input_index];
+  }
+}