I’m exporting a Houdini Pyro smoke sim as an OpenVDB sequence and importing it into UE5.6.
Workflow:
Houdini Pyro
→ OpenVDB sequence
→ UE5 Sparse Volume Texture
→ Heterogeneous Volume Actor
The issue happens in the thin, low-density smoke near the floor.
The thicker smoke looks mostly fine, but the fading transparent smoke tail becomes dotted / pixelated / blocky / flickery instead of smoothly fading out.
Below is the link to the video. I attached the link because it’s a new user.
There is also a secondary issue where character shadows become blocky on the smoke volume. But I can disable/fake the shadow if needed. The main issue I want to solve is the low-density smoke itself becoming dotted/pixelated.
With the help of AI, I tried several things to narrow down the cause:
Issue Blocking Requests ON
Streaming Mip Bias -1 / -2
Step Factor 0.5 / 0.25
Lighting Downsample Factor 0.1
Higher MRQ Temporal Samples
density 16-bit / 8-bit import
density-only import
Houdini Blast to keep only density
Houdini Volume Blur
Houdini Volume Wrangle to remove low-density values
In Houdini, I added a Volume Wrangle after the Pyro Solver to clean up the low-density smoke tail.
I tried a soft cutoff like this:
float cutoff = chf("cutoff");
float softness = chf("softness");
@density *= smooth(cutoff, cutoff + softness, @density);
I also tried a hard cutoff:
if (@density < 0.03)
{
@density = 0;
}
Issue Blocking Requests ON helped the most. It made the artifacts smaller, but they are still visible.
The original Houdini voxel size is 0.02.
I tried 0.01, but UE crashed / ran out of memory during import.
Has anyone solved this kind of low-density VDB smoke tail artifact in UE5 Heterogeneous Volumes / Sparse Volume Textures?
Any advice on Houdini export settings, UE import settings, material setup, or actor settings would be appreciated.
