In this tutorial, we will cover how to radically change the appearance of a volume using the VolumeSampleRGB shader to produce a thick, 'oily', smokey-looking volume. This shader along with the volume_sample_float shader has 'post-production' style attributes such as contrast and gamma . These attributes are very useful for 'fine tuning' the appearance of a volume . In this example, the VolumeSampleRGB shader has been used to convert a typical fire volume into something that looks more like thick smoke. We will use a default fire simulation from the Pyro FX shelf in Houdini that has been written to disk as a volume VDB.
The VDB file can be downloaded here . |
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The final scene (R18) can be downloaded here. |
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Enter 'density' into the channel attribute
Below are some other examples of changing the Volume Sample RGB shader's attributes:
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1 | 2 | 10 |
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0 | 1 | 8 |
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1 | 10 | 25 |
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-5 | 0 | 5 |
The final corrections used in this example involved adjusting the Gamma, Contrast and Exposure attributes as per the image below:
Final attributes for Volume Sample RGB
Increasing the volume ray depth can also have a dramatic affect on the appearance of the volume. Remember to increase the number of Volume Samples to compensate for any resulting noise. In this example, 6 Volume Samples was used.
When increasing the Volume Ray Depth, y ou may need to reduce the exposure of the scene lighting to compensate for the additional multiple scattering of illumination in the volume.
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0 | 6 |