Materials: support true float4 attributes in the Attribute node.

Add a new Alpha socket to the Attribute node that outputs the
fourth component of the attribute. Currently the only such
attribute is vertex color, but there may be more in the future.
If the attribute has no alpha channel, the expected value is 1.

The Cycles code is already refactored and committed by Brecht.

Ref D2057

1 files changed, 4 insertions, 1 deletions

diff --git a/source/blender/gpu/intern/gpu_node_graph.c b/source/blender/gpu/intern/gpu_node_graph.c
index c890d56994f..fdf8ba172cb 100644
--- a/source/blender/gpu/intern/gpu_node_graph.c
+++ b/source/blender/gpu/intern/gpu_node_graph.c
@@ -132,7 +132,10 @@ static void gpu_node_input_link(GPUNode *node, GPUNodeLink *link, const eGPUType
     case GPU_NODE_LINK_ATTR:
       input->source = GPU_SOURCE_ATTR;
       input->attr = link->attr;
-      input->attr->gputype = type;
+      /* Failsafe handling if the same attribute is used with different datatypes for
+       * some reason (only really makes sense with float/vec2/vec3/vec4 though). This
+       * can happen if mixing the generic Attribute node with specialized ones. */
+      CLAMP_MIN(input->attr->gputype, type);
       break;
     case GPU_NODE_LINK_CONSTANT:
       input->source = (type == GPU_CLOSURE) ? GPU_SOURCE_STRUCT : GPU_SOURCE_CONSTANT;