Unreal Engine Issues

UE-50204

SceneColor in surface material ignores translucent objects

SceneColor in surface material ignores translucent objects

Developer Notes

The SceneColor node behavior changed in 4.17.
Previously on 'every' draw call that sampled SceneColor it would make a NEW copy of the current SceneColor and then sample the copy. This is very expensive to the point that you shouldn't use it in production, and causes severe issues with doing parallel rendering on the translucent pass. Now the SceneColor node makes a single copy after Opaque rendering and all translucent materials sample that only via the node.

Questions & Answers
Description

Translucent meshes and particles behind an actor who's surface material uses SceneColor node are not rendered properly. Changing the view angle of the camera causes the translucent meshes to "pop" in and out of view. (see attached video)

This affects 4.17.1 and the 4.18 Preview

Regression:
Yes - Translucent meshes were always visible behind object with SceneColor material in 4.16.3 (CL 3561208)

Steps to Reproduce
  1. Open UE4 editor (first person template project)
  2. Add new material with settings shown in screenshot
  3. Apply material to any white cube in the viewport
  4. Reposition cube so it is over the "First Person Template" text on the floor
  5. Fly camera around, looking at the text through the cube

Result:
Depending on angle / distance, the text behind the box will vanish

Expected:
Text is always visible though the cube

Have Comments or More Details?

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By Design
ComponentUE - Graphics Features
Affects Versions4.17.1, 4.18
CreatedSep 22, 2017
ResolvedSep 26, 2017
UpdatedApr 27, 2018
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