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This can be textured simply by adding a regular UV set to the volumetric object (Planar, Cubic etc.) and a texture added to the material that's applied to the volumetric object. Procedural textures can also be used.
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Here, the checker procedural texture was used, and a planar projector applied to the volumetric object.
Texturing using the help of the extra grids
The first thing we need to determine is how many grids the VDB file has, and what their names are. To do this, simply load the file in your scene and click the render button from your main application, or from Studio. The intention is not to render the file at this time but simply to read what the Console panel in Maxwell tells us about the file. If the Console panel is not open, go to Window>Console and make sure it is checked.
In the above example we can see that we have a file with 3 grids. They are named: density, temperature, v (this grid is probably the velocity). They are of type float, float, vector respectively. Now that we know the names of the extra two grids, we can choose which one to use for generating the UVs, or in fact use both. In the "Additional grids for UV", we can write: temperature,v. This will generate two distinct UVs based on the temperature data and the velocity data. Lets use the temperature data. To be able to use these UVs, we must create a special type of UV set called VDB_FLOAT_00:.
Open the Type dropdown and choose the UV set VDB_FLOAT_00
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The UV set needs to be of type VDB Float because we are dealing with a VDB file, and the grid that's creating the UVs (the temperature grid in our case) is of type float. The reason we chose the "00" is because this is the first float grid that we are using. If we had two float grids that were generating UVs (both where specified in the "Additional grids for UV" parameter), and we wanted to use the second one, we would instead have chosen VDB_FLOAT_01. If there where 3 float grids specified and we wanted to use the third one, we would have chosen VDB_FLOAT_02 and so on. Please keep in mind that the count starts at 00, not 01.
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