VDB channels remapping questions

[johaneskurnia]

Hi there,

I have a couple of questions regarding reading VDBs from 3rd Party.

- What are the VrayVolumeGrid Smoke (density) & Temperature (liquid) expecting in terms of data type & range?
- Is there a data manipulation feature inside VrayVolumeGrid? If not, could use one

I managed to get velocity and color working apple-to-apple, only the Density & Liquid are a little bit in the unknown.

Thanks!
-Johanes

*ps: I am unable to post new thread in the General section, what should I do to be able to do this?

[Ivaylo Katev]

both the smoke and liquid are able to work in any range, because you have UI controls to adjust the smoke opacity and the liquid iso surface level. the liquid has one tricky moment, some products generate inverse liquid grid, i.e. the high value means air, the low value means liquid. this is because they export the liquid as distance to the surface, negative distance means underwater. in this case you have to put zero as surface level, and to enable the option "ïnvert volume"
about the general section, you have to ask the support for access , by default the users are allowed to post only in the public section

[Svetlin.Nikolov]

Hey,

If you have a Phoenix license, you should email Support to give you permissions for the other forum sections.

Phoenix/VolumeGrid generally do not depend on the data range and you can get any range to render:
- If you are rendering in Atmospheric/Volumetric mode, you should be working with the curves for mapping render fire/smoke to physical channels - there is a blue area in the curves that denotes the data range for the current frame.
- If you use the Mesh, Ocean, Cap or Isosurface modes, you pick your imported channel in the Surface combo on the rendering Panel and then adjust your Isosurface Level to something like the middle of the data range. If you don't know your data range, you can check it in the Preview section if you enable Auto-Range - then the preview will fit its min-max value to the data ranges of the selected channels for the current frame (we will take the ranges out to an easier-to-read place). If you get a full meshed box regardless of what Isosurface value you enter, you should try the "Invert volume" option - Phoenix/VolumeGrid expects by default the large values to be inside the mesh and the small ones - outside it, however e.g. Houdini level-sets are the opposite, so you need to invert.

You can check the nightly builds help - t's not completely up-to-date, but it covers the basic topics: http://docs.chaosgroup.com/display/P220N/Rendering

Cheers!

[johaneskurnia]

Thank you for the quick answers, they have solved my problems.

Cheers,
-Johanes

[Svetlin.Nikolov]

Glad to hear, cheers!