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, 17 insertions, 0 deletions

diff --git a/source/blender/gpu/intern/gpu_codegen.c b/source/blender/gpu/intern/gpu_codegen.c
index 39c3119cc39..c16fc08d1aa 100644
--- a/source/blender/gpu/intern/gpu_codegen.c
+++ b/source/blender/gpu/intern/gpu_codegen.c
@@ -377,6 +377,19 @@ static int codegen_process_uniforms_functions(GPUMaterial *material,
     BLI_freelistN(&ubo_inputs);
   }
 
+  /* Generate the uniform attribute UBO if necessary. */
+  if (!BLI_listbase_is_empty(&graph->uniform_attrs.list)) {
+    BLI_dynstr_append(ds, "\nstruct UniformAttributes {\n");
+    LISTBASE_FOREACH (GPUUniformAttr *, attr, &graph->uniform_attrs.list) {
+      BLI_dynstr_appendf(ds, "  vec4 attr%d;\n", attr->id);
+    }
+    BLI_dynstr_append(ds, "};\n");
+    BLI_dynstr_appendf(ds, "layout (std140) uniform %s {\n", GPU_ATTRIBUTE_UBO_BLOCK_NAME);
+    BLI_dynstr_append(ds, "  UniformAttributes uniform_attrs[DRW_RESOURCE_CHUNK_LEN];\n");
+    BLI_dynstr_append(ds, "};\n");
+    BLI_dynstr_append(ds, "#define GET_UNIFORM_ATTR(name) (uniform_attrs[resource_id].name)\n");
+  }
+
   BLI_dynstr_append(ds, "\n");
 
   return builtins;
@@ -480,6 +493,9 @@ static void codegen_call_functions(DynStr *ds, GPUNodeGraph *graph, GPUOutput *f
       else if (input->source == GPU_SOURCE_ATTR) {
         codegen_convert_datatype(ds, input->attr->gputype, input->type, "var", input->attr->id);
       }
+      else if (input->source == GPU_SOURCE_UNIFORM_ATTR) {
+        BLI_dynstr_appendf(ds, "GET_UNIFORM_ATTR(attr%d)", input->uniform_attr->id);
+      }
 
       BLI_dynstr_append(ds, ", ");
     }
@@ -799,6 +815,7 @@ GPUPass *GPU_generate_pass(GPUMaterial *material,
   /* Prune the unused nodes and extract attributes before compiling so the
    * generated VBOs are ready to accept the future shader. */
   gpu_node_graph_prune_unused(graph);
+  gpu_node_graph_finalize_uniform_attrs(graph);
 
   int builtins = 0;
   LISTBASE_FOREACH (GPUNode *, node, &graph->nodes) {