Reactions User Guide

Volume Material

The Volume Material controls the color, opacity and illumination of Volume Grid objects. It is made up of three main parts: Density, Scattering and Emission.

Density controls how thick and opaque the volume is. Scattering controls the color and brightness of the volume when another light source illuminates it. And Emission controls the color and brightness of the light emitted from the volume itself.


Parameters

Density

Grid Channel

Select the channel of the Volume Grid that will control the thickness and opacity. The most common choice is the "density" channel.

For more details on volume channels, see the Volume Grid/Channels section.

Remap

The values from the selected Grid Channel can be re-mapped using this curve. This allows making certain regions of the volume thicker or thinner without changing the simulation.

For more details on remapping curves, see Remapping Grid Channels.

Thickness

This parameter controls the overall thickness of the volume.

If this value is zero, the volume will be fully transparent and thus invisible. The larger the value is, the thicker and more opaque the volume will be.

Changing this parameter has the same effect as scaling the Remap curve along the Y axis.

Scattering

Grid Channel

Select the channel of the Volume Grid that will control the scattering color. If the channel is an RGB channel, its value will be used directly as the scattering color. Otherwise the channel value is mapped to a color using the Color Gradient parameter below.
The most common choice is the "density" channel.

For more details on volume channels, see the Volume Grid/Channels section.

Brightness

This value is used as a multiplier to the scattering color. Larger values will make the volume brighter.

Color Gradient

If the selected grid channel is not an RGB channel, this gradient assigns a color to every channel value. Typical gradients fade from dark to bright colors, s.t. small channel values are mapped to dark colors and large values to bright colors.

Emission

Grid Channel

Select the channel of the Volume Grid that will control the emission color and brightness. The "temperature" channel is a common choice here.

For more details on volume channels, see the Volume Grid/Channels section.

Remap

The values from the selected Grid Channel can be re-mapped using this curve. This allows changing the emission color and brightness of certain regions of the volume without changing the simulation.

For more details on remapping curves, see Remapping Grid Channels.

Intensity

Specifies the brightness of the emitted light. Values are often larger than one, 10 or even 100 as fire tends to have a high dynamic range.

Color Gradient

This gradient assigns a color to every channel value. Typical gradients fade from dark to bright colors, s.t. small channel values are mapped to dark colors and large values to bright colors.

Emission Scattering

A fast option to let emitted light illuminate the volume itself. This can be used to let fire illuminate smoke, creating the characteristic internal glow of a fireball.

Radius

The larger the radius, the farther the light will scatter. A radius of zero disables Emission Scattering.

Iterations

A higher iteration count approximates the physical scattering model better. Lower values render faster.

Emission Mask

This option can be used to darken or block entirely the emission of some parts of the volume.

Mask Channel

Select the channel of the Volume Grid that will control the emission masking. The "density" channel is a common choice here.

For more details on volume channels, see the Volume Grid/Channels section.

Mask Remap

The values from the selected Grid Channel can be re-mapped using this curve. This provides fine control over masking region and intensity.

For more details on remapping curves, see Remapping Grid Channels.

Quality

Step Size

This parameter controls the distance in voxels between the samples taken by the renderer. Lower values produces more accurate results and cost more render time.

Transmittance Threshold

Lower values produces more accurate results and cost more render time.

Remapping Grid Channels

TBD