Usability

- Cycles materials now render in Blender Internal too, skipping the nodes.
  Not very useful, but at least things then show up on renders and in
  previews.

- Node editor: if wrong shader nodes are in a tree, they draw with thene
  color RED ALERT headers now. (Switching render engine will show it).

2 files changed, 9 insertions, 2 deletions

diff --git a/source/blender/nodes/intern/node_exec.c b/source/blender/nodes/intern/node_exec.c
index 1889fd9a38e..061ec71d1e2 100644
--- a/source/blender/nodes/intern/node_exec.c
+++ b/source/blender/nodes/intern/node_exec.c
@@ -287,7 +287,7 @@ void ntreeReleaseThreadStack(bNodeThreadStack *nts)
 	nts->used = 0;
 }
 
-void ntreeExecThreadNodes(bNodeTreeExec *exec, bNodeThreadStack *nts, void *callerdata, int thread)
+int ntreeExecThreadNodes(bNodeTreeExec *exec, bNodeThreadStack *nts, void *callerdata, int thread)
 {
 	bNodeStack *nsin[MAX_SOCKET];	/* arbitrary... watch this */
 	bNodeStack *nsout[MAX_SOCKET];	/* arbitrary... watch this */
@@ -305,10 +305,17 @@ void ntreeExecThreadNodes(bNodeTreeExec *exec, bNodeThreadStack *nts, void *call
 			 * If the mute func is not set, assume the node should never be muted,
 			 * and hence execute it!
 			 */
+			if (node->typeinfo->compatibility != NODE_OLD_SHADING)
+				break;
 			if (node->typeinfo->execfunc)
 				node->typeinfo->execfunc(callerdata, node, nsin, nsout);
 			else if (node->typeinfo->newexecfunc)
 				node->typeinfo->newexecfunc(callerdata, thread, node, nodeexec->data, nsin, nsout);
 		}
 	}
+	
+	/* signal to switch back to no-node render */
+	if (node)
+		return 0;
+	return 1;
 }
diff --git a/source/blender/nodes/intern/node_exec.h b/source/blender/nodes/intern/node_exec.h
index 92ab0813bb1..679439ef12e 100644
--- a/source/blender/nodes/intern/node_exec.h
+++ b/source/blender/nodes/intern/node_exec.h
@@ -79,6 +79,6 @@ void ntree_exec_end(struct bNodeTreeExec *exec);
 
 struct bNodeThreadStack *ntreeGetThreadStack(struct bNodeTreeExec *exec, int thread);
 void ntreeReleaseThreadStack(struct bNodeThreadStack *nts);
-void ntreeExecThreadNodes(struct bNodeTreeExec *exec, struct bNodeThreadStack *nts, void *callerdata, int thread);
+int ntreeExecThreadNodes(struct bNodeTreeExec *exec, struct bNodeThreadStack *nts, void *callerdata, int thread);
 
 #endif