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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 holds the velocity information). 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 create UVs from this data, we must create a special type of UV set called VDB_FLOAT_00.
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Now that this special UV type has been added, we can add a texture to the material. We can leave the texture at channel 0, because we only have one UV set added to this object. In this case we added a gradient texture (please note that only the first row of pixels is used to texture the volumetric):
To accurately map the entire range of the gradient to the temperature UVs, we need to know the range of values found in the temperature grid. To do this, make sure "temperature" is written in the Additional grids for UV parameter and launch a render. In the Console panel, the values for this grid will now appear:
In the FLOAT_0 Max parameter enter the readout from the Console of the max range of the temperature grid: 0.884. We use the FLOAT_0 parameter because the temperature is the first additional grid we use, and it is of float type.
We can switch the UVs from the temperature grid, to the velocity grid. We need to first add another special UV set because now we are dealing with a vector grid. Add the UV set called VDB_VEC_MOD_00. Again, we add the "00" one because we only have one vector grid in this case. Now this object has two UV sets. For this reason, we also need to change the channel nr in the texture picker from 0 to 1, which tells Maxwell we want to use the second UV set that belongs to this object, and not the first one.
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