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Shadow catcher problem with holdout collection
Confirmed, NormalPublic


System Information
Operating system: Windows 10 Pro 64 bits
Graphics card: 2x NVIDIA GTX Titan X

Blender Version
Broken: master 2.81a
Worked: Worked on blender 2.79b

Short description of error
When shadow catcher is activated in an object located in a collection with the holdout option, alpha is truncated.
(more visible when there is motion blur)

Exact steps for others to reproduce the error
Based on the default startup :

  • set render engine to cycles
  • set Film parameters to Transparent
  • activate Motion Blur
  • set world backgound color to white (better visibility)
  • delete light
  • create a plane, scale x2
  • move plane to a new collection
  • set plane to shadow catcher
  • set collection 2 (called by default, with the plane) to holdout
  • animate camera for have motion blur (more visible when there is motion blur)
  • in viewport render, you will have that :
  • render.

without motion blur :

antialiasing problem

with motion blur :

same render result with and without alpha on composite node :

.Blender here :

Event Timeline

Richard Antalik (ISS) changed the task status from Needs Triage to Confirmed.Mon, Jan 27, 2:48 PM