Eevee: Use manual derivatives for better quality bump.

We basically duplicate the height map branch plugged into the bump node,
and tag each node in each branch as dx/dy/ref using `branch_tag`.

Then we add a one pixel offset on the texture coordinates if the node is
tagged as dx or dy.

The dx/dy branches are plugged into (new) hidden sockets on the bump node.

This match cycles bump better but have a performance impact. Also, complex
nodetrees can now become instruction limited and not compile anymore.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D5531

1 files changed, 2 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_node_types.h b/source/blender/makesdna/DNA_node_types.h
index ee5e9a13f66..6d2b278472f 100644
--- a/source/blender/makesdna/DNA_node_types.h
+++ b/source/blender/makesdna/DNA_node_types.h
@@ -276,7 +276,8 @@ typedef struct bNode {
   short preview_xsize, preview_ysize;
   /** Used at runtime when going through the tree. Initialize before use. */
   short tmp_flag;
-  char _pad2[2];
+  /** Used at runtime to tag derivatives branches. EEVEE only. */
+  short branch_tag;
   /** Runtime during drawing. */
   struct uiBlock *block;