Adds a scripted volume scatter model attribute to a material definition. This general volume scatter model type defines a new set of ray direction cosines based upon current ray position and direction cosines. The user also has access to individual ray wavelength which allows this feature to model volume fluorescence. This feature is not compatible for use with coherent raytracing.
This feature can be accessed in the following ways: •From a materials dialog select the "Volume Scatter" tab, then select "User defined volume Scatter (user-script)" as the type.
The user constructs a volume scatter definition based upon ray position (g_x, g_y, g_z), ray direction cosines (g_u, g_v, g_w) and uniform random number values (g_r1, g_r2, g_r3, g_r4). The ray output direction is returned in the form of direction cosines (g_uout, g_vout, g_wout). All values are expressed in the local coordinate system of the surface last intersected.
The default scripted volume scatter model is a Henyey-Greenstein model as shown below. A description of the mathematical approach is also included.
It is strongly recommended that the script make no modifications to other nodes in the FRED document.
If a change is made to the document during the raytrace by way of the scripted entity, the state of the document as seen by each individual thread of the raytrace will be inconsistently defined and the results of the raytrace may not be valid.
Scripted Volume Scatter Test Dialog Henyey-Greenstein Volume Scatter model
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