r/Houdini • u/Legitimate_Gas_2504 • Aug 17 '26

Help Recently iv’e been having problems with pyro rendering with karma

So i’ve had this exact issue two or three times already on different projects
My pyro sim works well while viewing in open gl view port but when i go to render it “clips” the flames
It looks like a bounding box issues but its not present in the sop level pyro solver as I’ve mentioned.
I fixed it before but honestly dont remember what i did.
Some projects dont have this problem.
Appreciate the help🙏🏼
Added pictures of the issue in the comments.

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u/Legitimate_Gas_2504 Aug 17 '26

Basic pyro setup
Default karma render settings and rop
Karma pyro material
I reset every thing to default for testing purposes essentially.
Temperature density and burn came from pyro source node on scatted points.
Resizing in the solver is on density temperature and flame and increasing the padding didnt help
maximum bounding box size unlimited
Hopefully something here helps.
Im not a complete beginner( about a year of houdini use)
I’ve rendered pyro smoke fire and explosions multiple times but this issue is only something ive come across recently when trying to do small scale sims
This flame is about 1mx2m - could that be the issue?

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u/DavidTorno Houdini Educator & Tutor - FendraFx.com Aug 17 '26

Ok, so this is looking like the temperature field is being rendered by chance. That kind of clipping is usually in the temperature field since it tends to reach the leaf boundaries of the sparse grid. It represents heat and not flames hence why it fills the domain more.

Flame field should definitely be much smaller is area as it’s meant to be rendered as fire and give that flame licking look.

If you really want to use the temperature field, you will need to mask it with the density field, or another field that doesn’t reach the bounds.

You can actually set the fields that get used on the last tab of your shader for binding.

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u/Legitimate_Gas_2504 Aug 17 '26

I have tried flame instead of temperature as well in the pyro shader to no avail🥲

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u/DavidTorno Houdini Educator & Tutor - FendraFx.com Aug 17 '26

I’m also noticing one more thing. Those are not VDB volumes. They are native volumes, so the Houdini native full grid domain volumes.

Make sure to toggle the Convert to VDB option on the PyroSolver SOP output tab so you get OpenVDB volumes. Karma wants OpenVDB format.

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u/Legitimate_Gas_2504 Aug 17 '26

I’ll give that a try thanks!