GPU: Add workaround for faulty default attrib values on some drivers

On some drivers, the default values is not respected correctly.

To workaround this we create a small VBO that contains only 1 vec4 worth of
data and just bind it using glBindVertexBuffer to ensure 0 stride.

This fixes T75069 Instances not rendered correctly by workbench.

1 files changed, 2 insertions, 0 deletions

diff --git a/source/blender/gpu/GPU_shader_interface.h b/source/blender/gpu/GPU_shader_interface.h
index 8b0d25e51a3..7a8900997d0 100644
--- a/source/blender/gpu/GPU_shader_interface.h
+++ b/source/blender/gpu/GPU_shader_interface.h
@@ -88,6 +88,8 @@ typedef struct GPUShaderInterface {
   char *name_buffer;
   struct GPUBatch **batches; /* references to batches using this interface */
   uint batches_len;
+  /** All enabled attribs in this shader. Used to set default values for unbound attribs. */
+  uint16_t enabled_attrib_mask;
 } GPUShaderInterface;
 
 GPUShaderInterface *GPU_shaderinterface_create(int32_t program_id);