Cycles Ambient Occlusion (AO) render pass produces different results depending on rendering device
Closed, ResolvedPublic

Description

System Information
Windows 10 64bit
Intel i5 3550
AMD Radeon RX480 4GB, (Crimson 17.5.1)

Blender Version
Broken: latest from Buildbot (2.78.5 0a6c57d)
Works: Blender 2.78c (official release)

Short description of error
Only and only when using OpenCL GPU rendering, the Ambient Occlusion render pass in Cycles appears to produce an output that goes beyond the 0...1 range. The result is that it makes the image brighter when used in a Multiply color node in the compositor. This does not occur with the latest official release.

Exact steps for others to reproduce the error
100% reproducible with the following steps steps and the attached .blend file:

  1. Render the image (F12)
  2. Adjust the Gamma setting for the AO pass in the node setup in the compositor
  3. Observe how after rendering the image with GPU OpenCL the behavior is different than with CPU rendering.