Name

The compound’s name. Enter any name you like, or leave the default.

Density Shape

(Textureable Input, per Particle) The texture carves away parts of the particle, starting at its edge. If the input texture is 0.0, the whole particle is gone; if the input is 1.0, nothing is carved away.

With the Intensity slider, you can scale the intensity of the input texture.

Density Limit

(Textureable Input, per Cloud or Gradient) Sets the maximum allowed density for the particle cloud (reduce this value for steam or thin smoke). If the value is high, the particle cloud shrinks if you reduce the density.

In the real world, steam particles are evenly spread in space; however, in 3D, you often have a higher density of particles in the inner parts of the volume and less density in the outer region. If you now reduce the density, the particle cloud seems to shrink because you don’t see the outer region, but the inner region still has enough density to be visible.

With this parameter, you can limit the density in the inner part of the cloud. If you now reduce the density of the whole volume, your cloud does not appear to shrink.

Override Particle Color

(Textureable Input, per Particle) Overrides the color of the particle using the input shader’s color.

Enable Cloud/Gradient Color/Density

Uses the color and/or density per cloud/gradient inputs.

Global Gradient Color

(Textureable Input, per Cloud or Gradient) Changes the color of the whole cloud.

With the Intensity slider, you can scale the mix amount of the color.

Global Gradient Density

(Textureable Input, per Cloud or Gradient) Changes the density for the whole cloud. The cloud density is multiplied with the input density.

With the Intensity slider, you can scale the amount of the density change.

You can use the same gradient shader which you have used for the color input.

Tint Ambient Color

Adjusts the ambient color of the volume.

Ambient Intensity

Intensity of the ambient shading.

Enable Illumination

Enables the illumination for the volume.

Tint Diffuse Color

Adjusts the diffuse color of the volume.

Diffuse Intensity

Intensity of the diffuse shading

Use Particle Color for Diffuse Illumination

The diffuse color is based on the particle color. If this option is off, the diffuse color is based only on the Tint Diffuse Color setting.

Ambient Occlusion

Calculates simple Ambient Occlusion (AO). The Ambient Occlusion is calculated for the lookup table. It does not take any normal direction into account. See Ambient Occlusion for more information.

Intensity

Modifies the intensity of the AO calculation.

AO Color

Color of the ambient occlusion.

Detail

Presets for the marching step settings. Low settings render in about 60% of the default settings time. With high settings, the volume takes twice the render time.

For information on marching steps, see Marching.

Cell Interpolation

Interpolation between the cells in the lookup table. For an explanation of the lookup table, see Lookup Table.

• No Interpolation between cells: No blending is done between the table cells. This is fast and should be used only to tweak the table size because you can see the voxels (cells).

• Linear: Simple interpolation (default) between the cells.

• Cubic: More complex calculation used for interpolation between the cells. Use this option if you can still see the the rows of the lookup table, but you already have enough table resolution to catch all shadows.

• Full Light Raytrace: This option is the slowest. Use it for very dense volumes with a very small edge falloff, such as volumes that have too much shadow detail for a lookup table. You need to set a cell size because the lookup table is used not only for shadows. The lookup table should cover the average shape of the volume (see Setting the Lookup Table for information).

Tile Size

Sets the size of the cells in the lookup table. For an explanation of the lookup table, see Lookup Table.

Memory Limit

While you are tuning the shader, you will probably reach the memory limit. This setting catches this case and prevents mental ray from stopping the rendering. It renders the volume with lower settings and in a red color.

Enable Fast Preview for Region

With this option on, you can easily switch the total render times by influencing the lookup table and ray length. You can also render the lookup table for tuning or render the volume in slices to check a texture. For more information, see Preview.