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Screen Space Reflections in EEVEE not working when using a Mix Node.
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Description

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 442.74

Blender Version
Broken: version: 2.82 (sub 7), branch: master, commit date: 2020-03-12 05:06, hash: rB375c7dc4caf4

Short description of error
Screen Space Reflections not working on material in which 2 shaders that include glossiness are connected to a Mix Shader when its factor is 1.0.

Exact steps for others to reproduce the error

  1. Enable Screen Space Reflections in EEVEE's rendered mode.
  2. Create a material that has 2 shaders (anyr shaders that have glossiness, like Glossy or Principled BSDF).
  3. Connect those two shaders to a Mix Shader node.
  4. When the factor of the Mix Shader is at 0, screen space reflections are visible. When the factor is at 1, they don't.

Including images to show the issue:


.blend file with an example (please, enable rendered mode and tweak the factor of the Mix Shader node to see the reflections):

Event Timeline

For the developers wondering, this persists in Blender 2.83 with the version I tested being 10f0e003a95a

This bug however does not occur when you use the same material for both the inputs of the mix shader node.

This is a known limitation. See https://docs.blender.org/manual/en/latest/render/eevee/limitations.html#screen-space-reflections

  • Only one glossy BSDF can emit screen space reflections.
  • The evaluated BSDF is currently arbitrarily chosen.