# Path Tracing Vdb problem **URL:** \ **Category:** Rendering\ **Tags:** Path-Tracer, unreal-engine, path, question\ **Created:** [March 24, 2024, 1:03pm UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813 "2024-03-24T13:03:39Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![VlastelinSeksa](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@VlastelinSeksa](https://forums.unrealengine.com/u/VlastelinSeksa)\ **Post date:** [March 24, 2024, 1:03pm UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/1 "2024-03-24T13:03:39Z")
Hi all. I have VDB fire imported from Embergen. And it doesn’t show up in Path Tracing. I know that I need to enter the command r.pathtracing.heterogeneous volumes 1 but after that nothing changes, the VDB is still not visible. ---
**Author:** ![Crackbundle](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Crackbundle](https://forums.unrealengine.com/u/Crackbundle)\ **Post date:** [April 29, 2024, 5:27pm UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/2 "2024-04-29T17:27:10Z")
I’m having the same exact issue. Have you found a solution? ---
**Author:** ![JimboKrumm](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@JimboKrumm](https://forums.unrealengine.com/u/JimboKrumm)\ **Post date:** [June 19, 2024, 3:20pm UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/3 "2024-06-19T15:20:00Z")
Any updates on this?? I can’t find anything anywhere. The ‘ r.pathtracing.heterogeneous volumes’ command isn’t even listed as a real variable anymore. ---
**Author:** ![KosasihDre](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@KosasihDre](https://forums.unrealengine.com/u/KosasihDre)\ **Post date:** [July 25, 2024, 1:32am UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/4 "2024-07-25T01:32:06Z")
Hey there! Happening to me too. The command doesn’t appear as well. Hope there is a solution! ---
**Author:** ![Kaido1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Kaido1](https://forums.unrealengine.com/u/Kaido1)\ **Post date:** [September 28, 2024, 10:10pm UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/5 "2024-09-28T22:10:46Z")
hello, i need the solution for this exact same problem you have something??? ---
**Author:** ![az4q](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@az4q](https://forums.unrealengine.com/u/az4q)\ **Post date:** [October 30, 2024, 9:19am UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/6 "2024-10-30T09:19:23Z")
found solution? ---
**Author:** ![comlys](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/comlys/32/998665_2.png) [@comlys](https://forums.unrealengine.com/u/comlys)\ **Post date:** [October 30, 2024, 8:07pm UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/7 "2024-10-30T20:07:32Z")
What version of the engine are you on? ---
**Author:** ![az4q](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@az4q](https://forums.unrealengine.com/u/az4q)\ **Post date:** [November 1, 2024, 10:10am UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/8 "2024-11-01T10:10:17Z")
5.4.4 ---
**Author:** ![comlys](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/comlys/32/998665_2.png) [@comlys](https://forums.unrealengine.com/u/comlys)\ **Post date:** [November 1, 2024, 6:55pm UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/9 "2024-11-01T18:55:51Z")
I would say it should _just work_ but there are a couple of required controls to juggle the shading rate and the memory usage. The defaults are: `r.HeterogeneousVolumes.FrustumGrid.ShadingRate 4 r.HeterogeneousVolumes.FrustumGrid.MaxBottomLevelMemoryInMegabytes 128` Lowering the shading rate takes the HV voxels closer to the size of a pixel (1), but each halving of the shading rate incurs a 4X increase in voxel density and required memory. If you haven’t allocated enough memory, the volume builder just drops the voxels [the result being that dropped voxels simply disappear]. ---
**Author:** ![az4q](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@az4q](https://forums.unrealengine.com/u/az4q)\ **Post date:** [November 4, 2024, 10:57am UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/10 "2024-11-04T10:57:05Z")
did not work, can ue work with flame attribute in path tracing, just seeems to me that does not. For example this fire can not be seen in pt ![{0BEFD449-1AAC-49E8-AE2B-E76EED591E85}](https://d3kjluh73b9h9o.cloudfront.net/original/4X/6/5/c/65cfcc39628be50fee6c764c15e0f64930ac790e.jpeg) ---
**Author:** ![CartmanSouth](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@CartmanSouth](https://forums.unrealengine.com/u/CartmanSouth)\ **Post date:** [February 14, 2025, 2:51pm UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/11 "2025-02-14T14:51:51Z")
> [@comlys](#): > > r.HeterogeneousVolumes.FrustumGrid.ShadingRate 4 Thank You so much! I spent hours to find out why my vdb-s are pixelated in pathtrace mode. ---
**Author:** ![Mad\_Sky\_2000](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Mad\_Sky\_2000](https://forums.unrealengine.com/u/Mad_Sky_2000)\ **Post date:** [August 21, 2026, 2:42am UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/12 "2026-08-21T02:42:29Z")
I am having the same issue. i am using 5.8 ---
**Author:** ![Mad\_Sky\_2000](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Mad\_Sky\_2000](https://forums.unrealengine.com/u/Mad_Sky_2000)\ **Post date:** [August 21, 2026, 2:52am UTC](https://forums.unrealengine.com/t/path-tracing-vdb-problem/1769813/13 "2026-08-21T02:52:01Z")
never mind, there was something wrong with my vdb. if you want to make sure your vdb is fine, download PixelLap’s VDB Shader and use its default vdb preview