Volumes are objects made of density, such as fire or clouds.
Rendering of volumes should not be confused with Atmospheric Volume Scattering, which is a global effect.
Volumes can only receive indirect lighting from other emissive volumes when the Volume Ray Depth is above 0.
Volume Formats
- Rendering volumes with HtoA only works with OpenVDB files or VDB primtives.
- You can also develop your own volume plugin with the new volume API, see Implementing a Volume DSO.
- It is also possible to render particles as volume, with access to particle attributes as user data.
- You can also render polymeshes as volumes.
Volume Nodes
- Arnold Volume - Arnold volume object node.
- Standard Volume - Shader that defines the volume shading properties.
- Volume Sample RGB and Float - Shaders that sample a volume channel.
Render Quality
Several parameters affect the overall quality of volume rendering:
- On the Arnold ROP: Volume Diffuse Samples
On the Arnold Light: Volume Samples
On the Arnold Volume: Step Size
Volumes and Atmosphere Volume
Currently, Atmosphere Volume does not compose well against volumes. This is because atmosphere's return a single flat result that is opacity mapped on top of whatever is in the background of the pixel.
Left: floor plane geometry hidden. Right: floor plane geometry visible. Fluid renders incorrectly. Click images above to view animation.
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Further examples