Materials: add custom object properties as uniform attributes.

This patch allows the user to type a property name into the
Attribute node, which will then output the value of the property
for each individual object, allowing to e.g. customize shaders
by object without duplicating the shader.

In order to make supporting this easier for Eevee, it is necessary
to explicitly choose whether the attribute is varying or uniform
via a dropdown option of the Attribute node. The dropdown also
allows choosing whether instancing should be taken into account.

The Cycles design treats all attributes as one common namespace,
so the Blender interface converts the enum to a name prefix that
can't be entered using keyboard.

In Eevee, the attributes are provided to the shader via a UBO indexed
with resource_id, similar to the existing Object Info data. Unlike it,
however, it is necessary to maintain a separate buffer for every
requested combination of attributes.

This is done using a hash table with the attribute set as the key,
as it is expected that technically different but similar materials
may use the same set of attributes. In addition, in order to minimize
wasted memory, a sparse UBO pool is implemented, so that chunks that
don't contain any data don't have to be allocated.

The back-end Cycles code is already refactored and committed by Brecht.

Differential Revision: https://developer.blender.org/D2057

1 files changed, 18 insertions, 0 deletions

diff --git a/source/blender/draw/intern/draw_manager_exec.c b/source/blender/draw/intern/draw_manager_exec.c
index 808b5cc675b..21bcaa2d2b2 100644
--- a/source/blender/draw/intern/draw_manager_exec.c
+++ b/source/blender/draw/intern/draw_manager_exec.c
@@ -57,12 +57,15 @@ typedef struct DRWCommandsState {
   /* Resource location. */
   int obmats_loc;
   int obinfos_loc;
+  int obattrs_loc;
   int baseinst_loc;
   int chunkid_loc;
   int resourceid_loc;
   /* Legacy matrix support. */
   int obmat_loc;
   int obinv_loc;
+  /* Uniform Attributes. */
+  DRWSparseUniformBuf *obattrs_ubo;
   /* Selection ID state. */
   GPUVertBuf *select_buf;
   uint select_id;
@@ -648,6 +651,12 @@ static void draw_update_uniforms(DRWShadingGroup *shgroup,
           state->obinfos_loc = uni->location;
           GPU_uniformbuf_bind(DST.vmempool->obinfos_ubo[0], uni->location);
           break;
+        case DRW_UNIFORM_BLOCK_OBATTRS:
+          state->obattrs_loc = uni->location;
+          state->obattrs_ubo = DRW_uniform_attrs_pool_find_ubo(DST.vmempool->obattrs_ubo_pool,
+                                                               uni->uniform_attrs);
+          DRW_sparse_uniform_buffer_bind(state->obattrs_ubo, 0, uni->location);
+          break;
         case DRW_UNIFORM_RESOURCE_CHUNK:
           state->chunkid_loc = uni->location;
           GPU_shader_uniform_int(shgroup->shader, uni->location, 0);
@@ -762,6 +771,10 @@ static void draw_call_resource_bind(DRWCommandsState *state, const DRWResourceHa
       GPU_uniformbuf_unbind(DST.vmempool->obinfos_ubo[state->resource_chunk]);
       GPU_uniformbuf_bind(DST.vmempool->obinfos_ubo[chunk], state->obinfos_loc);
     }
+    if (state->obattrs_loc != -1) {
+      DRW_sparse_uniform_buffer_unbind(state->obattrs_ubo, state->resource_chunk);
+      DRW_sparse_uniform_buffer_bind(state->obattrs_ubo, chunk, state->obattrs_loc);
+    }
     state->resource_chunk = chunk;
   }
 
@@ -884,6 +897,9 @@ static void draw_call_batching_finish(DRWShadingGroup *shgroup, DRWCommandsState
   if (state->obinfos_loc != -1) {
     GPU_uniformbuf_unbind(DST.vmempool->obinfos_ubo[state->resource_chunk]);
   }
+  if (state->obattrs_loc != -1) {
+    DRW_sparse_uniform_buffer_unbind(state->obattrs_ubo, state->resource_chunk);
+  }
 }
 
 static void draw_shgroup(DRWShadingGroup *shgroup, DRWState pass_state)
@@ -893,11 +909,13 @@ static void draw_shgroup(DRWShadingGroup *shgroup, DRWState pass_state)
   DRWCommandsState state = {
       .obmats_loc = -1,
       .obinfos_loc = -1,
+      .obattrs_loc = -1,
       .baseinst_loc = -1,
       .chunkid_loc = -1,
       .resourceid_loc = -1,
       .obmat_loc = -1,
       .obinv_loc = -1,
+      .obattrs_ubo = NULL,
       .drw_state_enabled = 0,
       .drw_state_disabled = 0,
   };