EEVEE: ScreenSpaceReflections: Improve hit quality

This changes the hitBuffer to store `ReflectionDir * HitTime, invPdf`
just as the reference presentation.

This avoids issues when the hit refinement produce a coordinate that
does not land on the correct surface.

We now store the pdf in the same texture and store it inversed so we can
remove some ALU from the resolve shader.

This also rewrite the resolve shader to not be vectorized to improve
readability and scalability.

1 files changed, 2 insertions, 3 deletions

diff --git a/source/blender/draw/engines/eevee/eevee_private.h b/source/blender/draw/engines/eevee/eevee_private.h
index 45afee31591..eb1c51f49dd 100644
--- a/source/blender/draw/engines/eevee/eevee_private.h
+++ b/source/blender/draw/engines/eevee/eevee_private.h
@@ -737,7 +737,6 @@ typedef struct EEVEE_EffectsInfo {
   struct GPUTexture *ssr_normal_input; /* Textures from pool */
   struct GPUTexture *ssr_specrough_input;
   struct GPUTexture *ssr_hit_output;
-  struct GPUTexture *ssr_pdf_output;
   /* Temporal Anti Aliasing */
   int taa_reproject_sample;
   int taa_current_sample;
@@ -854,8 +853,8 @@ typedef struct EEVEE_EffectsInfo {
  * - Arrays of vec2/vec3 are padded as arrays of vec4.
  * - sizeof(bool) == sizeof(int) in GLSL so use int in C */
 typedef struct EEVEE_CommonUniformBuffer {
-  float prev_persmat[4][4]; /* mat4 */
-  float hiz_uv_scale[4];    /* vec4 */
+  float prev_persmat[4][4];               /* mat4 */
+  float hiz_uv_scale[2], ssr_uv_scale[2]; /* vec4 */
   /* Ambient Occlusion */
   /* -- 16 byte aligned -- */
   float ao_dist, pad1, ao_factor, pad2;                    /* vec4 */