EEVEE: Renderlayer artifacts

When rendering the Subsurface scattering lighting render layer with high
sample count render artifacts can appear. This patch will remove these
render artifacts by using a more precise texture format when samples
will be larger than 128. As with the new eevee-shadows it is more common
to use higher number of samples.

The reason why it was visible in the subsurface scattering is that every
sample could change the color. Adding different values will reduce
precision over the number of samples.

The subsurface color render layer also has this issue, but it is not noticeable as
the colors tend to be close to each other so the colors would
most of the time just shift the precision and hold up better.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D6245

4 files changed, 27 insertions, 17 deletions

diff --git a/source/blender/draw/engines/eevee/eevee_occlusion.c b/source/blender/draw/engines/eevee/eevee_occlusion.c
index 48e9b5bcc13..0a7d1db1061 100644
--- a/source/blender/draw/engines/eevee/eevee_occlusion.c
+++ b/source/blender/draw/engines/eevee/eevee_occlusion.c
@@ -131,7 +131,7 @@ int EEVEE_occlusion_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
   return 0;
 }
 
-void EEVEE_occlusion_output_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
+void EEVEE_occlusion_output_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata, uint tot_samples)
 {
   EEVEE_FramebufferList *fbl = vedata->fbl;
   EEVEE_TextureList *txl = vedata->txl;
@@ -143,11 +143,13 @@ void EEVEE_occlusion_output_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata
   const Scene *scene_eval = DEG_get_evaluated_scene(draw_ctx->depsgraph);
 
   if (scene_eval->eevee.flag & SCE_EEVEE_GTAO_ENABLED) {
+    const eGPUTextureFormat texture_format = (tot_samples > 128) ? GPU_R32F : GPU_R16F;
+
     DefaultTextureList *dtxl = DRW_viewport_texture_list_get();
     float clear[4] = {0.0f, 0.0f, 0.0f, 0.0f};
 
     /* Should be enough precision for many samples. */
-    DRW_texture_ensure_fullscreen_2d(&txl->ao_accum, GPU_R32F, 0);
+    DRW_texture_ensure_fullscreen_2d(&txl->ao_accum, texture_format, 0);
 
     GPU_framebuffer_ensure_config(&fbl->ao_accum_fb,
                                   {GPU_ATTACHMENT_NONE, GPU_ATTACHMENT_TEXTURE(txl->ao_accum)});
diff --git a/source/blender/draw/engines/eevee/eevee_private.h b/source/blender/draw/engines/eevee/eevee_private.h
index 7d02aacfac7..41e38fd8437 100644
--- a/source/blender/draw/engines/eevee/eevee_private.h
+++ b/source/blender/draw/engines/eevee/eevee_private.h
@@ -988,7 +988,9 @@ void EEVEE_bloom_free(void);
 
 /* eevee_occlusion.c */
 int EEVEE_occlusion_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata);
-void EEVEE_occlusion_output_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata);
+void EEVEE_occlusion_output_init(EEVEE_ViewLayerData *sldata,
+                                 EEVEE_Data *vedata,
+                                 uint tot_samples);
 void EEVEE_occlusion_output_accumulate(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata);
 void EEVEE_occlusion_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata);
 void EEVEE_occlusion_compute(EEVEE_ViewLayerData *sldata,
@@ -1009,7 +1011,9 @@ void EEVEE_screen_raytrace_free(void);
 void EEVEE_subsurface_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata);
 void EEVEE_subsurface_draw_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata);
 void EEVEE_subsurface_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata);
-void EEVEE_subsurface_output_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata);
+void EEVEE_subsurface_output_init(EEVEE_ViewLayerData *sldata,
+                                  EEVEE_Data *vedata,
+                                  uint tot_samples);
 void EEVEE_subsurface_add_pass(EEVEE_ViewLayerData *sldata,
                                EEVEE_Data *vedata,
                                uint sss_id,
diff --git a/source/blender/draw/engines/eevee/eevee_render.c b/source/blender/draw/engines/eevee/eevee_render.c
index 75e837f140b..ee1dc8a0208 100644
--- a/source/blender/draw/engines/eevee/eevee_render.c
+++ b/source/blender/draw/engines/eevee/eevee_render.c
@@ -517,9 +517,17 @@ void EEVEE_render_draw(EEVEE_Data *vedata, RenderEngine *engine, RenderLayer *rl
   GPU_framebuffer_bind(fbl->main_fb);
   DRW_hair_update();
 
+  uint tot_sample = scene_eval->eevee.taa_render_samples;
+  uint render_samples = 0;
+
+  /* SSR needs one iteration to start properly. */
+  if (stl->effects->enabled_effects & EFFECT_SSR) {
+    tot_sample += 1;
+  }
+
   if ((view_layer->passflag & (SCE_PASS_SUBSURFACE_COLOR | SCE_PASS_SUBSURFACE_DIRECT |
                                SCE_PASS_SUBSURFACE_INDIRECT)) != 0) {
-    EEVEE_subsurface_output_init(sldata, vedata);
+    EEVEE_subsurface_output_init(sldata, vedata, tot_sample);
   }
 
   if ((view_layer->passflag & SCE_PASS_MIST) != 0) {
@@ -527,21 +535,13 @@ void EEVEE_render_draw(EEVEE_Data *vedata, RenderEngine *engine, RenderLayer *rl
   }
 
   if ((view_layer->passflag & SCE_PASS_AO) != 0) {
-    EEVEE_occlusion_output_init(sldata, vedata);
+    EEVEE_occlusion_output_init(sldata, vedata, tot_sample);
   }
 
-  uint tot_sample = scene_eval->eevee.taa_render_samples;
-  uint render_samples = 0;
-
   if (RE_engine_test_break(engine)) {
     return;
   }
 
-  /* SSR needs one iteration to start properly. */
-  if (stl->effects->enabled_effects & EFFECT_SSR) {
-    tot_sample += 1;
-  }
-
   while (render_samples < tot_sample && !RE_engine_test_break(engine)) {
     float clear_col[4] = {0.0f, 0.0f, 0.0f, 0.0f};
     float clear_depth = 1.0f;
diff --git a/source/blender/draw/engines/eevee/eevee_subsurface.c b/source/blender/draw/engines/eevee/eevee_subsurface.c
index 8376b8c67b8..a7c28347c15 100644
--- a/source/blender/draw/engines/eevee/eevee_subsurface.c
+++ b/source/blender/draw/engines/eevee/eevee_subsurface.c
@@ -156,7 +156,9 @@ static void set_shgrp_stencil(void *UNUSED(userData), DRWShadingGroup *shgrp)
   DRW_shgroup_stencil_mask(shgrp, 255);
 }
 
-void EEVEE_subsurface_output_init(EEVEE_ViewLayerData *UNUSED(sldata), EEVEE_Data *vedata)
+void EEVEE_subsurface_output_init(EEVEE_ViewLayerData *UNUSED(sldata),
+                                  EEVEE_Data *vedata,
+                                  uint tot_samples)
 {
   EEVEE_FramebufferList *fbl = vedata->fbl;
   EEVEE_TextureList *txl = vedata->txl;
@@ -164,8 +166,10 @@ void EEVEE_subsurface_output_init(EEVEE_ViewLayerData *UNUSED(sldata), EEVEE_Dat
   EEVEE_EffectsInfo *effects = stl->effects;
 
   if (effects->enabled_effects & EFFECT_SSS) {
-    DRW_texture_ensure_fullscreen_2d(&txl->sss_dir_accum, GPU_RGBA16F, 0);
-    DRW_texture_ensure_fullscreen_2d(&txl->sss_col_accum, GPU_RGBA16F, 0);
+    const eGPUTextureFormat texture_format_light = (tot_samples > 128) ? GPU_RGBA32F : GPU_RGBA16F;
+    const eGPUTextureFormat texture_format_color = (tot_samples > 512) ? GPU_RGBA32F : GPU_RGBA16F;
+    DRW_texture_ensure_fullscreen_2d(&txl->sss_dir_accum, texture_format_light, 0);
+    DRW_texture_ensure_fullscreen_2d(&txl->sss_col_accum, texture_format_color, 0);
 
     GPUTexture *stencil_tex = effects->sss_stencil;