In this tutorial we will go through how to setup and use the Volume Sample Float shader to adjust the color temperature effect of an OpenVDB file, using the temperature and density VDB grids.

The scene file can be downloaded here.

A tutorial on how to write volumes to OpenVDB from Houdini can be found here.

 

 

Arnold volume settings. Grids set to 'density' and 'temperature'.

Standard Volume 

 

Ramp RGB

Ramp RGB recreate's color temperature of explosion

Volume Sample Float

We can use a Volume Sample Float shader to control the appearance of our fire volume effect. This shader will remap the values of the 3D voxel grid in the same manner as tone-mapping and remapping filters to an image in Photoshop, which operates in a 2D grid.

 

Final Volume Sample Float attributes

Final shader network

 

Volume Sample Float Attributes

We can use the Volume Sample Float shader to alter the appearance of the explosion. The following images show different adjustment attributes and their effect on the explosion volume.

Input Max

Bias

Output Max