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, 14 insertions, 15 deletions

diff --git a/source/blender/draw/engines/eevee/eevee_screen_raytrace.c b/source/blender/draw/engines/eevee/eevee_screen_raytrace.c
index 80a1c9fcbe5..00004b28ef3 100644
--- a/source/blender/draw/engines/eevee/eevee_screen_raytrace.c
+++ b/source/blender/draw/engines/eevee/eevee_screen_raytrace.c
@@ -77,6 +77,7 @@ int EEVEE_screen_raytrace_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
       common_data->ssr_firefly_fac = FLT_MAX;
     }
 
+    void *owner = (void *)EEVEE_screen_raytrace_init;
     const int divisor = (effects->reflection_trace_full) ? 1 : 2;
     int tracing_res[2] = {(int)viewport_size[0] / divisor, (int)viewport_size[1] / divisor};
     const int size_fs[2] = {(int)viewport_size[0], (int)viewport_size[1]};
@@ -86,22 +87,22 @@ int EEVEE_screen_raytrace_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
     tracing_res[0] = max_ii(1, tracing_res[0]);
     tracing_res[1] = max_ii(1, tracing_res[1]);
 
+    common_data->ssr_uv_scale[0] = size_fs[0] / ((float)tracing_res[0] * divisor);
+    common_data->ssr_uv_scale[1] = size_fs[1] / ((float)tracing_res[1] * divisor);
+
     /* MRT for the shading pass in order to output needed data for the SSR pass. */
-    effects->ssr_specrough_input = DRW_texture_pool_query_2d(
-        size_fs[0], size_fs[1], format, &draw_engine_eevee_type);
+    effects->ssr_specrough_input = DRW_texture_pool_query_2d(UNPACK2(size_fs), format, owner);
 
     GPU_framebuffer_texture_attach(fbl->main_fb, effects->ssr_specrough_input, 2, 0);
 
     /* Ray-tracing output. */
-    effects->ssr_hit_output = DRW_texture_pool_query_2d(
-        tracing_res[0], tracing_res[1], GPU_RG16I, &draw_engine_eevee_type);
-    effects->ssr_pdf_output = DRW_texture_pool_query_2d(
-        tracing_res[0], tracing_res[1], GPU_R16F, &draw_engine_eevee_type);
+    effects->ssr_hit_output = DRW_texture_pool_query_2d(UNPACK2(tracing_res), GPU_RGBA16F, owner);
 
     GPU_framebuffer_ensure_config(&fbl->screen_tracing_fb,
-                                  {GPU_ATTACHMENT_NONE,
-                                   GPU_ATTACHMENT_TEXTURE(effects->ssr_hit_output),
-                                   GPU_ATTACHMENT_TEXTURE(effects->ssr_pdf_output)});
+                                  {
+                                      GPU_ATTACHMENT_NONE,
+                                      GPU_ATTACHMENT_TEXTURE(effects->ssr_hit_output),
+                                  });
 
     return EFFECT_SSR | EFFECT_NORMAL_BUFFER | EFFECT_RADIANCE_BUFFER | EFFECT_DOUBLE_BUFFER |
            ((use_refraction) ? EFFECT_REFRACT : 0);
@@ -111,7 +112,6 @@ int EEVEE_screen_raytrace_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
   GPU_FRAMEBUFFER_FREE_SAFE(fbl->screen_tracing_fb);
   effects->ssr_specrough_input = NULL;
   effects->ssr_hit_output = NULL;
-  effects->ssr_pdf_output = NULL;
 
   return 0;
 }
@@ -148,7 +148,6 @@ void EEVEE_screen_raytrace_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *v
      */
     DRW_PASS_CREATE(psl->ssr_raytrace, DRW_STATE_WRITE_COLOR);
     DRWShadingGroup *grp = DRW_shgroup_create(trace_shader, psl->ssr_raytrace);
-    DRW_shgroup_uniform_texture_ref(grp, "depthBuffer", &e_data.depth_src);
     DRW_shgroup_uniform_texture_ref(grp, "normalBuffer", &effects->ssr_normal_input);
     DRW_shgroup_uniform_texture_ref(grp, "specroughBuffer", &effects->ssr_specrough_input);
     DRW_shgroup_uniform_texture_ref(grp, "maxzBuffer", &txl->maxzbuffer);
@@ -164,17 +163,17 @@ void EEVEE_screen_raytrace_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *v
     }
     DRW_shgroup_call(grp, quad, NULL);
 
+    eGPUSamplerState no_filter = GPU_SAMPLER_DEFAULT;
+
     DRW_PASS_CREATE(psl->ssr_resolve, DRW_STATE_WRITE_COLOR | DRW_STATE_BLEND_ADD);
     grp = DRW_shgroup_create(resolve_shader, psl->ssr_resolve);
-    DRW_shgroup_uniform_texture_ref(grp, "depthBuffer", &e_data.depth_src);
     DRW_shgroup_uniform_texture_ref(grp, "normalBuffer", &effects->ssr_normal_input);
     DRW_shgroup_uniform_texture_ref(grp, "specroughBuffer", &effects->ssr_specrough_input);
     DRW_shgroup_uniform_texture_ref(grp, "probeCubes", &lcache->cube_tx.tex);
     DRW_shgroup_uniform_texture_ref(grp, "probePlanars", &vedata->txl->planar_pool);
     DRW_shgroup_uniform_texture_ref(grp, "planarDepth", &vedata->txl->planar_depth);
-    DRW_shgroup_uniform_texture_ref(grp, "hitBuffer", &effects->ssr_hit_output);
-    DRW_shgroup_uniform_texture_ref(grp, "pdfBuffer", &effects->ssr_pdf_output);
-    DRW_shgroup_uniform_texture_ref(grp, "prevColorBuffer", &txl->filtered_radiance);
+    DRW_shgroup_uniform_texture_ref_ex(grp, "hitBuffer", &effects->ssr_hit_output, no_filter);
+    DRW_shgroup_uniform_texture_ref(grp, "colorBuffer", &txl->filtered_radiance);
     DRW_shgroup_uniform_texture_ref(grp, "maxzBuffer", &txl->maxzbuffer);
     DRW_shgroup_uniform_texture_ref(grp, "shadowCubeTexture", &sldata->shadow_cube_pool);
     DRW_shgroup_uniform_texture_ref(grp, "shadowCascadeTexture", &sldata->shadow_cascade_pool);