Hi all,

I'm new to Houdini and loving it so far. I've been playing with octane to speed up renders lately and I'm having an issue with smoke voxel size. I can't seem to refine this resolution with settings that I would normally use.

I've tried adjusting the division size for the smoke which is what I would normally do for mantra, but it doesn't seem to work in same way. I've tried converting to vdb and outputting a vdb sequence which would work except I get a vdb error expecting version 223 instead of 224.

Any help with this would be appreciated.

Thanks

Also new and encountering this problem - any help would be great!

Thanks

I just stumbled-upon this thread, and wanted to update in case others had the same question regarding the VDB version errors.

According the the OpenVDB and RenderMan forums, the ‘unsupported VDB file format (expected version 223 or earlier, got version 224)’ errors can be ignored. If you're seeing rendering artifacts, and you're not using Point Data Grids, than the problem is probably from something else in the scene setup.

Hope this helps.

https://groups.google.com/forum/# [groups.google.com]!topic/openvdb-forum/oDOXUyXyYLs
https://rmanwiki.pixar.com/display/RfH/OpenVDB [rmanwiki.pixar.com]

This has to do with the medium step length and density settings in Octane. Octane can only render VDB volumes so Houdini will convert it's volume to VDB at a voxel resolution relative to the pyro smoke object division. Houdini (read: Mantra) will still use this same voxel size but there's a subvoxel interpolation that happens so you don't see this effect. This is not an error or artifact. This is simple because in a VDB vile you have a voxel with properties such as density (in smoke) and heat, temperature, fuel, velocities in addition to density (for most pyrofx objects). These properties are distributed uniformly in the voxel in a VDB grid.

The easy but slow solution: decrease your division size which increases voxel resolution (“Do I look like I know what a jaypeg is?”). Just make sure to upgrade your memory first. I've been able to get some fantastic Pyro and fluid sims out of Houdini with Octane. But one just has to understand the way octane interprets these volumes. Barring that, you'll have to play with step length and density. You can often times hide the edges of the voxels by tuning those two settings. But in my humble opinion, if you want high resolution, detailed smoke or fire, you're going to have to simulate at a higher resolution (upres won't necessarily work as if you simulate as a lower resolution and then upres, you're not really simulating at the higher res just interpolating what should theoretically be there. If the gap between simulated resolution and the upres target resolution is too high, it won't move naturally.

Crank it up!!!