Material for Volume

Panels for matrial setting is shown in property panel by clicking material icon.

Material setting for volume determines color, density and several other options.

Coloring

Basic color setting is similar to materials for object.

In Original and Basic Shader Mode, color of volume depends only on color curve and value of data, so that material color does not affect the coloring. They have meanings in Phong and Scattering Shader.

Texture

Interpolate

The way texture would interpolated.

The second combobox determines the behavior at the edge of texture.
In usual case, there is little difference between them.
However, if texture space is deformed by some modifiers, this can be important.

This image shows four volume data of CT scan data of human head. The original data is at right, and other data is transformed vie texture space modifier with "Clamp at Edge", "Repeat", and "Clamp" mode respectively.
As you can see, the way for showing region outside of the range [0, 1] is determined by this option.

VolumeShader

Shader determines the way faces are colored. Currently, following predefined shaders for volume rendering exist. Note that volume data itself is

Original	Use default OpenGL pipeline. Since data source is 1 byte colorless data, volume is expressed as grayscale with no transparency information.
Volume Basic	Color (and its transparency or alpha) is evaluated via color curve.
Volume Phong	Diffse scattering is evaluated like Phong shading. It is evaluated by the direction of differentiation of volume data instead of normal of faces.
Volume Scatter	Coloring will be modified by the angle between light and camera view. This is a clude way to mimic a object with different forward and backward scattring parameter.

Volume Basic(left), Volume Phong (middle), Volume scatter (right). Lower rows are volume with self shadow.

Self Shadow

Calculate self shadowing of volume. It gives more realistic taste but with considerble rendering cost.
Note that volume data can not cast shadows on other objects. Only self shadowing would be calculated.

Shader Quality

Quality factor of shader. Currently, it works only on self shadowing calculation.

Scatter Factor

This parameter is used for volume scatter shader. Full forward scattering is 1, while full back scattering is set to -1.

Color Curve

Source of volume data is colorless scalar value.
The volume would be colored via color curve.

Color curve can be edited in Color Curve Editor. When Color Curve Editor is on the window, clicking the color curve on the material panel make it active (or editable on the editor).

Option

Discard 0

In some data, value 0 may mean outside of the region, and you may want use dense color for low value. Setting color curve for such abrupt change can be bothersome. If this option is checked, the area with value 0 is forced to be alpha = 0.

Additive / Depth Mask

These options are similar to that in material for basic objects.

return