DRW-Next: Add uniform attributes (object attributes) support

This replaces the direct shader uniform layout declaration by a linear
search through a global buffer.

Each instance has an attribute offset inside the global buffer and an
attribute count.

This removes any padding and tighly pack all uniform attributes inside
a single buffer.

This would also remove the limit of 8 attribute but it is kept because of
compatibility with the old system that is still used by the old draw
manager.

1 files changed, 23 insertions, 0 deletions

diff --git a/source/blender/draw/engines/eevee_next/shaders/eevee_nodetree_lib.glsl b/source/blender/draw/engines/eevee_next/shaders/eevee_nodetree_lib.glsl
index 13ad387289d..491e15341f9 100644
--- a/source/blender/draw/engines/eevee_next/shaders/eevee_nodetree_lib.glsl
+++ b/source/blender/draw/engines/eevee_next/shaders/eevee_nodetree_lib.glsl
@@ -409,3 +409,26 @@ vec4 attr_load_color_post(vec4 attr)
 #endif
 
 /** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Volume Attribute post
+ *
+ * TODO(@fclem): These implementation details should concern the DRWManager and not be a fix on
+ * the engine side. But as of now, the engines are responsible for loading the attributes.
+ *
+ * \{ */
+
+vec4 attr_load_uniform(vec4 attr, const uint attr_hash)
+{
+#if defined(OBINFO_LIB) && defined(OBATTR_LIB)
+  for (int i = ObjectAttributeStart; i < ObjectAttributeLen; i++) {
+    if (drw_attrs[i].hash_code == attr_hash) {
+      return vec4(
+          drw_attrs[i].data_x, drw_attrs[i].data_y, drw_attrs[i].data_z, drw_attrs[i].data_w);
+    }
+  }
+#endif
+  return attr;
+}
+
+/** \} */