Octane Volume Medium

Volume mediums add color and other qualities to a VDB file. VDBs are a generic Volume format that creates effects such as smoke, fog, vapor, and similar gaseous Objects.

VDBs can be a single frame, or an animated file sequence. The Volume Medium Node is often connected to a Material Output node's Medium input pin.

Several attributes affect the output of the Volume Medium:

• The correct volume step length

• Ray epsilon (in the Render Target Kernel)

• GI clamp (in the Render Target Kernel)

• Settings in the volume denoiser (imager camera)

• Max Samples (in the render kernel)

• Optional Volume Ramp Node

• Max diffuse depth (Path Tracing Kernel)

• Absorption - By default, the absorption attribute is controlled by a color value ranging from 0 - 255 for each color channel where 0 is no absorption and 255 is full absorption. A texture (via an Texture Image node) can be added to replace the value slider. The color's value and saturation can be used to further determine the absorption amount.

• Scattering - Determines how quickly light scatters as it moves through the surface. High values mean that light scatters sooner as it enters the surface, and low values mean that light passes deeper into the surface before it scatters. By default, the scattering attribute is controlled by a value slide ranging from 0 - 1 where 0 is no scattering and 1 is full scattering. A color or texture can be added to replace the value slider. The color's value and saturation can be used to further determine the scatter amount.

• Density - Determines the density of the particles in the surface. The larger the density value, the more likely light will be absorbed when passing through the surface.

• Volume Step Length - The default value is 4, but if the volume is smaller than this, you need to decrease the value. Decreasing this value decreases render speed, and increasing the value causes the ray marching algorithm to take longer steps. If this value exceeds the volume's dimensions, then the ray marching algorithm takes a single step through the whole volume. To get the most accurate results, keep this value as small as possible.

• Use Volume Step for Shadows - Checkbox to turn on Volume Step Length for Shadows.

• Shadow Step Length - Step length that is used by the shadow ray for marching through volumes

• Phase - Input pin for the Phase Function.

• Invert Scattering - Inverts the function of the Scattering function.