EEVEE: Arbitrary Output Variables

This patch adds support for AOVs in EEVEE. AOV Outputs can be defined in the
render pass tab and used in shader materials. Both Object and World based
shaders are supported. The AOV can be previewed in the viewport using the
renderpass selector in the shading popover.

AOV names that conflict with other AOVs are automatically corrected. AOV
conflicts with render passes get a warning icon. The reason behind this is that
changing render engines/passes can change the conflict, but you might not notice
it. Changing this automatically would also make the materials incorrect, so best
to leave this to the user.

**Implementation**

The patch adds a copies the AOV structures of Cycles into Blender. The goal is
that the Cycles will use Blenders AOV defintions. In the Blender kernel
(`layer.c`) the logic of these structures are implemented.

The GLSL shader of any GPUMaterial can hold multiple outputs (the main output
and the AOV outputs) based on the renderPassUBO the right output is selected.
This selection uses an hash that encodes the AOV structure. The full AOV needed
to be encoded when actually drawing the material pass as the AOV type changes
the behavior of the AOV. This isn't known yet when the GLSL is compiled.

**Future Developments**

* The AOV definitions in the render layer panel isn't shared with Cycles.
  Cycles should be migrated to use the same viewlayer aovs. During a previous
  attempt this failed as the AOV validation in cycles and in Blender have
  implementation differences what made it crash when an aov name was invalid.
  This could be fixed by extending the external render engine API.
* Add support to Cycles to render AOVs in the 3d viewport.
* Use a drop down list for selecting AOVs in the AOV Output node.
* Give user feedback when multiple AOV output nodes with the same AOV name
  exists in the same shader.
* Fix viewing single channel images in the image editor [T83314]
* Reduce viewport render time by only render needed draw passes. [T83316]

Reviewed By: Brecht van Lommel, Clément Foucault

Differential Revision: https://developer.blender.org/D7010

1 files changed, 15 insertions, 4 deletions

diff --git a/source/blender/draw/engines/eevee/eevee_private.h b/source/blender/draw/engines/eevee/eevee_private.h
index f5cef8f3c25..1385721a569 100644
--- a/source/blender/draw/engines/eevee/eevee_private.h
+++ b/source/blender/draw/engines/eevee/eevee_private.h
@@ -53,6 +53,7 @@ extern struct DrawEngineType draw_engine_eevee_type;
 #define MAX_SHADOW_CASCADE 8
 #define MAX_SHADOW_CUBE (MAX_SHADOW - MAX_CASCADE_NUM * MAX_SHADOW_CASCADE)
 #define MAX_BLOOM_STEP 16
+#define MAX_AOVS 64
 
 // #define DEBUG_SHADOW_DISTRIBUTION
 
@@ -163,8 +164,9 @@ BLI_INLINE bool eevee_hdri_preview_overlay_enabled(const View3D *v3d)
 #define EEVEE_RENDERPASSES_MATERIAL \
   (EEVEE_RENDER_PASS_EMIT | EEVEE_RENDER_PASS_DIFFUSE_COLOR | EEVEE_RENDER_PASS_DIFFUSE_LIGHT | \
    EEVEE_RENDER_PASS_SPECULAR_COLOR | EEVEE_RENDER_PASS_SPECULAR_LIGHT | \
-   EEVEE_RENDER_PASS_ENVIRONMENT)
-
+   EEVEE_RENDER_PASS_ENVIRONMENT | EEVEE_RENDER_PASS_AOV)
+#define EEVEE_AOV_HASH_ALL -1
+#define EEVEE_AOV_HASH_COLOR_TYPE_MASK 1
 /* Material shader variations */
 enum {
   VAR_MAT_MESH = (1 << 0),
@@ -376,6 +378,7 @@ typedef struct EEVEE_TextureList {
   struct GPUTexture *diff_light_accum;
   struct GPUTexture *spec_color_accum;
   struct GPUTexture *spec_light_accum;
+  struct GPUTexture *aov_surface_accum[MAX_AOVS];
   struct GPUTexture *emit_accum;
   struct GPUTexture *bloom_accum;
   struct GPUTexture *ssr_accum;
@@ -430,7 +433,9 @@ typedef struct EEVEE_RenderPassData {
   int renderPassEmit;
   int renderPassSSSColor;
   int renderPassEnvironment;
-  int _pad[1];
+  int renderPassAOV;
+  int renderPassAOVActive;
+  int _pad[3];
 } EEVEE_RenderPassData;
 
 /* ************ LIGHT UBO ************* */
@@ -860,6 +865,7 @@ typedef struct EEVEE_ViewLayerData {
     struct GPUUniformBuf *spec_color;
     struct GPUUniformBuf *spec_light;
     struct GPUUniformBuf *emit;
+    struct GPUUniformBuf *aovs[MAX_AOVS];
   } renderpass_ubo;
 
   /* Common Uniform Buffer */
@@ -959,6 +965,9 @@ typedef struct EEVEE_PrivateData {
   /* Renderpasses */
   /* Bitmask containing the active render_passes */
   eViewLayerEEVEEPassType render_passes;
+  int aov_hash;
+  int num_aovs_used;
+
   /* Uniform references that are referenced inside the `renderpass_pass`. They are updated
    * to reuse the drawing pass and the shading group. */
   int renderpass_type;
@@ -1284,10 +1293,12 @@ void EEVEE_renderpasses_output_accumulate(EEVEE_ViewLayerData *sldata,
                                           bool post_effect);
 void EEVEE_renderpasses_postprocess(EEVEE_ViewLayerData *sldata,
                                     EEVEE_Data *vedata,
-                                    eViewLayerEEVEEPassType renderpass_type);
+                                    eViewLayerEEVEEPassType renderpass_type,
+                                    int aov_index);
 void EEVEE_renderpasses_draw(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata);
 void EEVEE_renderpasses_draw_debug(EEVEE_Data *vedata);
 bool EEVEE_renderpasses_only_first_sample_pass_active(EEVEE_Data *vedata);
+int EEVEE_renderpasses_aov_hash(const ViewLayerAOV *aov);
 
 /* eevee_temporal_sampling.c */
 void EEVEE_temporal_sampling_reset(EEVEE_Data *vedata);