BaseVolume

Overview

BaseVolume is a volume shader meant to be applied to a water tight mesh. The volume is homogenous by default but can be made heterogenous by binding maps to any of the attributes. Map bindings are evaluated and baked into the grid based on the bake_resolution_mode.


Attribute Reference

Volume attributes

anisotropy

Float bindable
default: 0.0

Value in the interval [-1,1] that defines how foward (1) or backward (-1) scattering the volume is. A value of 0.0 indicates an isotropic volume.

anisotropy: -1 | 1 (backlit)

attenuation_color

Rgb bindable
default: [ 1, 1, 1 ]

A color multiplier for the attenuation. The resulting color will be the inverse of the color set with this parameter.

attenuation_color: (0,0,0) | (1,1,1)

attenuation_factor

Float bindable
default: 1.0

An additional factor to scale the attenuation. This attribute behaves identically to attenuation_intensity - it is provided simply as an extra way to control attenuation, typically during lighting. Surfacing should generally avoid setting this.

attenuation_factor: 0 | 1

attenuation_intensity

Float bindable
default: 1.0

The rate at which the intensity of a ray traversing a volume is lost. The attenuation (extinction) coefficient is the product of attenuation_color, attenuation_intensity, and attenuation_factor

attenuation_intensity: 0 | 1

diffuse_color

Rgb bindable
default: [ 1, 1, 1 ]

Reflectance color (scattering albedo) of the volume.

diffuse_color: (0,0,0) | (1,1,1)

emission_color

Rgb bindable
default: [ 0, 0, 0 ]

A color multiplier for the emission. The product of emission color and intensity is the emission coefficient

emission_color: (0,0,0) | (1,1,1)

emission_intensity

Float bindable
default: 1.0

The rate at which a volume emits light at a given point. The product of emission color and intensity is the emission coefficient.

emission_intensity: 0 | 1

surface_opacity_threshold

Float
default: 0.5

Accumulated opacity that's considered the 'surface' for computing surface position and Z

Volume Baking attributes

bake_divisions

Int
default: 100

Divide widest axis by this many divisions

bake_resolution_mode

Int enum
  0 = “default” (default)
  1 = “divisions”
  2 = “voxel size”

Method to specify grid resolution of baked density grid. Choices are:
  "default": For shaders that are bound to vdb volumes, use vdb resolution.
      For shaders that are bounds to mesh geometries use 100 divisions
  "divisions": Specify number of divisions.
  "voxel size": Specify voxel size.

bake_voxel_size

Float
default: 10.0

Size of voxel in world space

General attributes

label

String
default:

label used in light aovs