Unreal Engine Issues

UE-17338

GPU Particle Collision changes based on Normal Intensity on Colliding Surface

GPU Particle Collision changes based on Normal Intensity on Colliding Surface

Developer Notes

By design. Scene depth collision uses the per-pixel normals for collision so obviously changing how the material calculates normals will change collision behavior.
In this case multiplying the normal by 10 and then normalize likely pushes the normal towards values tangent to the real surface. When we reconstruct the plane on the GPU using that normal the plane will not match the geometry.

Questions & Answers
Description

Increasing the intensity of a Normal Texture on a colliding surface will cause the collision of GPU particles to behave strangely, looks to be falling through floor, when you are using a Constant Acceleration module.

Also reproduced in Launcher 4.8.0-2579680 and Main Promotable-CL-2589716

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Steps to Reproduce

Open Attached the Project for Instant Reproduction

  1. Create a GPU Particle System with a Constant Acceleration fo -980 and Collision
  2. Create a Material with a Normal Texture and increase its intensity by 10.
  3. Add the Material to the Floor
  4. Place the GPU Particle Immediately above the Floor
  5. Adjust the intensity of the Normal back to 1.

RESULTS: Particles will bounce once and disappear through the floor until the Normal intensity is lowered

EXPECTED: Normal Intensity should not affect GPU Collision.

Community References

GPU Particle collision with normals on material

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By Design
ComponentUE - Graphics Features
Affects Versions4.7.6, 4.8, 4.9
CreatedJun 18, 2015
ResolvedJun 18, 2015
UpdatedJul 14, 2021