Volume Grid and VDB

[bibi5000]

Hello,

i want to import a VDB sequence from Houdini to 3dsMax.
The Simulation has quite a big bounding box and a high resolution but there are only a few locations with activated voxels.
In Houdini i get a count of 7mio voxels. If i import this into a volumegrid object in 3dsmax i get a counter of 2 billion voxel
and it says "grid size too big! Cannot import grid!...". It seems to ignore that this is a sparse volume.

Thanks in advance!

[vlado]

The volume grid does not support sparse volumes right now. We'll get to that later, but in the meantime if you can break that into separate VDB files, it will work.

Best regards,
Vlado

[bibi5000]

Thanx Vlado,

for my task its quite complicated to split the volumes up.
does the Volume Grid fully expand all voxel that are in the bounding box?
And isnt it possible to disable the skipping of too large grids for vdbs?
Is it possible with Phoenix to import sparse data without any restrictions?

Thx for your help

[Svetlin.Nikolov]

Hello,

The VolumeGrid and Phoenix do exactly the same - it's the same code underneath, so it's just a matter of which version you use so you will have an improved version of it. Sparse grids or grids with different resolution for e.g. density versus velocity, are converted to a single big grid with the finest resolution among all available channels. A couple of months back we made it so if a grid has more than 2.1 billion voxels, it's automatically downsampled to 2.1 - I think this is yet to enter an official service pack and is only in the nightles. Anyway, obviously this eats up detail, so hopefully in the next couple of weeks we will have proper sparse grid support for Phoenix and the volume grid.

[Dan Andersen]

Hello,
Anyway, obviously this eats up detail, so hopefully in the next couple of weeks we will have proper sparse grid support for Phoenix and the volume grid.

It's been a couple weeks - is this working now? Reading sparse volumes.

[Svetlin.Nikolov]

Sure, it's been there for a few years

Some things you have to watch out for - there are a few options that would create dense grids when rendering on CPU:
- Grid based self illumination
- Volume Light Cache
- Optimize Big Volumetric Grids

So you can turn these off and follow the tips here to make sure you are getting the best performance: https://docs.chaosgroup.com/display/...ering+In-Depth

Rendering in Mesh mode would also use a dense grid underneath, so if you want to render a surface, make sure to use Isosurface mode instead.

Cheers!

[Dan Andersen]

That's great news . And this would apply to VRay for Maya / Houdini as well?

[Svetlin.Nikolov]

Yup, the implementation underneath is the same

[Dan Andersen]

Happy to hear. Thanks for confirming