Fix for [#24293] Shadow pass is wrong

* The problem is that shadow pass is derived from the diffuse pass as
  shad = shad'/diff, where shad' = shad*diff. In cases where diff is
  0 and the division can't be done shad is left as shad' (=0).
* This all works just fine until the diffuse color is 0 on just one
  channel (no red in material color for example). In this case the shadow
  pass is left as 0 too regardless of the existence of an actual shadow,
  so the end result is a colored shadow!
* The only real solution is to use the original shadow intensity to
  determine if there actually is a shadow or not. This is now stored in
  shr->shad[3] from the lamp shadow calculation.

Note: The best solution would probably be to calculate the shadow pass on
it's own and not to derive it from the diffuse pass, but I didn't dare to
start messing up the shading code totally.

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/render/extern/include/RE_shader_ext.h b/source/blender/render/extern/include/RE_shader_ext.h
index 6cab4a7ce03..71ce269fce6 100644
--- a/source/blender/render/extern/include/RE_shader_ext.h
+++ b/source/blender/render/extern/include/RE_shader_ext.h
@@ -52,7 +52,7 @@ typedef struct ShadeResult
 	float emit[3];
 	float diff[3];		/* no ramps, shadow, etc */
 	float spec[3];
-	float shad[3];
+	float shad[4];		/* shad[3] is shadow intensity */
 	float ao[3];
 	float env[3];
 	float indirect[3];