EEVEE: Render Passes

This patch adds new render passes to EEVEE. These passes include:

* Emission
* Diffuse Light
* Diffuse Color
* Glossy Light
* Glossy Color
* Environment
* Volume Scattering
* Volume Transmission
* Bloom
* Shadow

With these passes it will be possible to use EEVEE effectively for
compositing. During development we kept a close eye on how to get similar
results compared to cycles render passes there are some differences that
are related to how EEVEE works. For EEVEE we combined the passes to
`Diffuse` and `Specular`. There are no transmittance or sss passes anymore.
Cycles will be changed accordingly.

Cycles volume transmittance is added to multiple surface col passes. For
EEVEE we left the volume transmittance as a separate pass.

Known Limitations

* All materials that use alpha blending will not be rendered in the render
  passes. Other transparency modes are supported.
* More GPU memory is required to store the render passes. When rendering
  a HD image with all render passes enabled at max extra 570MB GPU memory is
  required.

Implementation Details

An overview of render passes have been described in
https://wiki.blender.org/wiki/Source/Render/EEVEE/RenderPasses

Future Developments

* In this implementation the materials are re-rendered for Diffuse/Glossy
  and Emission passes. We could use multi target rendering to improve the
  render speed.
* Other passes can be added later
* Don't render material based passes when only requesting AO or Shadow.
* Add more passes to the system. These could include Cryptomatte, AOV's, Vector,
  ObjectID, MaterialID, UV.

Reviewed By: Clément Foucault

Differential Revision: https://developer.blender.org/D6331

1 files changed, 89 insertions, 0 deletions

diff --git a/source/blender/draw/engines/eevee/eevee_volumes.c b/source/blender/draw/engines/eevee/eevee_volumes.c
index 7026894076a..456673c92fa 100644
--- a/source/blender/draw/engines/eevee/eevee_volumes.c
+++ b/source/blender/draw/engines/eevee/eevee_volumes.c
@@ -54,6 +54,7 @@ static struct {
   struct GPUShader *scatter_with_lights_sh;
   struct GPUShader *volumetric_integration_sh;
   struct GPUShader *volumetric_resolve_sh;
+  struct GPUShader *volumetric_accum_sh;
 
   GPUTexture *depth_src;
 
@@ -73,6 +74,7 @@ extern char datatoc_common_view_lib_glsl[];
 extern char datatoc_octahedron_lib_glsl[];
 extern char datatoc_irradiance_lib_glsl[];
 extern char datatoc_lights_lib_glsl[];
+extern char datatoc_volumetric_accum_frag_glsl[];
 extern char datatoc_volumetric_frag_glsl[];
 extern char datatoc_volumetric_geom_glsl[];
 extern char datatoc_volumetric_vert_glsl[];
@@ -136,6 +138,8 @@ static void eevee_create_shader_volumes(void)
                                                             datatoc_volumetric_resolve_frag_glsl,
                                                             e_data.volumetric_common_lib,
                                                             NULL);
+  e_data.volumetric_accum_sh = DRW_shader_create_fullscreen(datatoc_volumetric_accum_frag_glsl,
+                                                            NULL);
 
   float color[4] = {1.0f, 1.0f, 1.0f, 1.0f};
   e_data.dummy_density = DRW_texture_create_3d(1, 1, 1, GPU_RGBA8, DRW_TEX_WRAP, color);
@@ -359,6 +363,8 @@ void EEVEE_volumes_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
       DRW_shgroup_uniform_block(grp, "planar_block", sldata->planar_ubo);
       DRW_shgroup_uniform_block(grp, "light_block", sldata->light_ubo);
       DRW_shgroup_uniform_block(grp, "shadow_block", sldata->shadow_ubo);
+      DRW_shgroup_uniform_block(
+          grp, "renderpass_block", EEVEE_material_default_render_pass_ubo_get(sldata));
 
       /* Fix principle volumetric not working with world materials. */
       DRW_shgroup_uniform_texture(grp, "sampdensity", e_data.dummy_density);
@@ -375,6 +381,8 @@ void EEVEE_volumes_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
     /* If no world or volume material is present just clear the buffer with this drawcall */
     grp = DRW_shgroup_create(e_data.volumetric_clear_sh, psl->volumetric_world_ps);
     DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
+    DRW_shgroup_uniform_block(
+        grp, "renderpass_block", EEVEE_material_default_render_pass_ubo_get(sldata));
 
     DRW_shgroup_call_procedural_triangles(grp, NULL, common_data->vol_tex_size[2]);
   }
@@ -430,8 +438,12 @@ void EEVEE_volumes_cache_object_add(EEVEE_ViewLayerData *sldata,
   DRW_shgroup_uniform_block(grp, "shadow_block", sldata->shadow_ubo);
   DRW_shgroup_uniform_block(grp, "light_block", sldata->light_ubo);
   DRW_shgroup_uniform_block(grp, "grid_block", sldata->grid_ubo);
+  DRW_shgroup_uniform_block(
+      grp, "renderpass_block", EEVEE_material_default_render_pass_ubo_get(sldata));
 
   DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
+  DRW_shgroup_uniform_block(
+      grp, "renderpass_block", EEVEE_material_default_render_pass_ubo_get(sldata));
   DRW_shgroup_uniform_vec3(grp, "volumeOrcoLoc", texcoloc, 1);
   DRW_shgroup_uniform_vec3(grp, "volumeOrcoSize", texcosize, 1);
 
@@ -522,6 +534,8 @@ void EEVEE_volumes_cache_finish(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
     DRW_shgroup_uniform_block(grp, "light_block", sldata->light_ubo);
     DRW_shgroup_uniform_block(grp, "shadow_block", sldata->shadow_ubo);
     DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
+    DRW_shgroup_uniform_block(
+        grp, "renderpass_block", EEVEE_material_default_render_pass_ubo_get(sldata));
 
     DRW_shgroup_call_procedural_triangles(grp, NULL, common_data->vol_tex_size[2]);
 
@@ -530,6 +544,8 @@ void EEVEE_volumes_cache_finish(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
     DRW_shgroup_uniform_texture_ref(grp, "volumeScattering", &txl->volume_scatter);
     DRW_shgroup_uniform_texture_ref(grp, "volumeExtinction", &txl->volume_transmit);
     DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
+    DRW_shgroup_uniform_block(
+        grp, "renderpass_block", EEVEE_material_default_render_pass_ubo_get(sldata));
 
     DRW_shgroup_call_procedural_triangles(
         grp, NULL, USE_VOLUME_OPTI ? 1 : common_data->vol_tex_size[2]);
@@ -540,6 +556,8 @@ void EEVEE_volumes_cache_finish(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
     DRW_shgroup_uniform_texture_ref(grp, "inTransmittance", &txl->volume_transmit);
     DRW_shgroup_uniform_texture_ref(grp, "inSceneDepth", &e_data.depth_src);
     DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
+    DRW_shgroup_uniform_block(
+        grp, "renderpass_block", EEVEE_material_default_render_pass_ubo_get(sldata));
 
     DRW_shgroup_call_procedural_triangles(grp, NULL, 1);
   }
@@ -729,4 +747,75 @@ void EEVEE_volumes_free(void)
   DRW_SHADER_FREE_SAFE(e_data.scatter_with_lights_sh);
   DRW_SHADER_FREE_SAFE(e_data.volumetric_integration_sh);
   DRW_SHADER_FREE_SAFE(e_data.volumetric_resolve_sh);
+  DRW_SHADER_FREE_SAFE(e_data.volumetric_accum_sh);
+}
+
+/* -------------------------------------------------------------------- */
+
+/** \name Render Passes
+ * \{ */
+
+void EEVEE_volumes_output_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata, uint tot_samples)
+{
+  EEVEE_FramebufferList *fbl = vedata->fbl;
+  EEVEE_TextureList *txl = vedata->txl;
+  EEVEE_StorageList *stl = vedata->stl;
+  EEVEE_PassList *psl = vedata->psl;
+  EEVEE_EffectsInfo *effects = stl->effects;
+
+  float clear[4] = {0.0f, 0.0f, 0.0f, 0.0f};
+
+  /* Create FrameBuffer. */
+
+  /* Should be enough precision for many samples. */
+  const eGPUTextureFormat texture_format_accum = (tot_samples > 128) ? GPU_RGBA32F : GPU_RGBA16F;
+  DRW_texture_ensure_fullscreen_2d(&txl->volume_scatter_accum, texture_format_accum, 0);
+  DRW_texture_ensure_fullscreen_2d(&txl->volume_transmittance_accum, texture_format_accum, 0);
+
+  GPU_framebuffer_ensure_config(&fbl->volumetric_accum_fb,
+                                {GPU_ATTACHMENT_NONE,
+                                 GPU_ATTACHMENT_TEXTURE(txl->volume_scatter_accum),
+                                 GPU_ATTACHMENT_TEXTURE(txl->volume_transmittance_accum)});
+
+  /* Clear texture. */
+  if (DRW_state_is_image_render() || effects->taa_current_sample == 1) {
+    GPU_framebuffer_bind(fbl->volumetric_accum_fb);
+    GPU_framebuffer_clear_color(fbl->volumetric_accum_fb, clear);
+  }
+
+  /* Create Pass and shgroup. */
+  DRW_PASS_CREATE(psl->volumetric_accum_ps, DRW_STATE_WRITE_COLOR | DRW_STATE_BLEND_ADD_FULL);
+  DRWShadingGroup *grp = NULL;
+  if ((effects->enabled_effects & EFFECT_VOLUMETRIC) != 0) {
+    grp = DRW_shgroup_create(e_data.volumetric_resolve_sh, psl->volumetric_accum_ps);
+    DRW_shgroup_uniform_texture_ref(grp, "inScattering", &txl->volume_scatter);
+    DRW_shgroup_uniform_texture_ref(grp, "inTransmittance", &txl->volume_transmit);
+    DRW_shgroup_uniform_texture_ref(grp, "inSceneDepth", &e_data.depth_src);
+    DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
+    DRW_shgroup_uniform_block(
+        grp, "renderpass_block", EEVEE_material_default_render_pass_ubo_get(sldata));
+  }
+  else {
+    /* There is no volumetrics in the scene. Use a shader to fill the accum textures with a default
+     * value. */
+    grp = DRW_shgroup_create(e_data.volumetric_accum_sh, psl->volumetric_accum_ps);
+  }
+  DRW_shgroup_call(grp, DRW_cache_fullscreen_quad_get(), NULL);
 }
+
+void EEVEE_volumes_output_accumulate(EEVEE_ViewLayerData *UNUSED(sldata), EEVEE_Data *vedata)
+{
+  EEVEE_FramebufferList *fbl = vedata->fbl;
+  EEVEE_PassList *psl = vedata->psl;
+
+  if (fbl->volumetric_accum_fb != NULL) {
+    /* Accum pass */
+    GPU_framebuffer_bind(fbl->volumetric_accum_fb);
+    DRW_draw_pass(psl->volumetric_accum_ps);
+
+    /* Restore */
+    GPU_framebuffer_bind(fbl->main_fb);
+  }
+}
+
+/* \} */