Hi,

I am doing some pyro simulation, exporting result as VDB. I have the following two questions:

1) Is it possible to see the max/min range for temperature and density fields? Even more, can I see the entire range of values in a list view just as we view point attributes in the geometry spreadsheet? I want to do so because I am rendering in an external renderer and it will help see the values of density/temperature so I can fine tune the renderer shading parameters…

2) I am not sure if this is even valid for not, but Houdini produces one VDB per frame (i.e. when I use ROP output driver, it stores file.01.vdb, file.02.vdb or in general file.$F.vdb). Now, my question is there such a thing to store ALL vdb files in one big file? i.e. one file that has vdb in different time frames? I am not sure if this exists or not, but I am just doing some basic research…

Thanks,

1. VDB primitives lack min/max intrinsics, but you can use a volume slice and play with min/max values and watch the colors.
   
2. Why would you want a value spreadsheet? A list of millions of values seems of little use. The volume slice SOP is useful for visualizing ranges/prevalence of values.
   
3. There is no multi-frame vdb storage container that I know of. If you want to make an archive just for storage purposes, you could tarball or zip them up. For rendering/use they would need to be extracted.
   

Alright…Thanks for your help I don't really need to see ALL values I just wanted to know min/max values so I can fine tune shading parameters, but will test your method as it should be enough… Once more, thanks for your help

to see all the values in spreadsheet you can use VDB Visualize Tree
uncheck everything except Active Voxels and check Points With values, then you will see values of all voxel values in spreadsheet

or as jsmack indirectly hinted, to get just min/max you can convert to houdini voulume and then look at volumeminvalue/volumemaxvalue intrinsics or use Volume Reduce

Thanks tamte

Just an update, one other user on odforce suggested that before converting the pyro simulation into vdb, I can just use expressions volumemin/volumemax to read min/max values and it did work… just wanted to share

also there is a check box on Dop Import Fields sop, compute min max, you can examine those as primitive attribs for each field

Those min / max values will only be for the current frame. Before you convert to VDB you
can go the geometry spreadsheet, primitive tab, and enable min / max prim intrinsics, that will give you
the values you are after.