## Volume rendering with a separate opacity array

The **Volume** representation has a new option for specifying that a separate array should be used
for opacity mapping. Additionally, options for choosing the opacity array and component (or vector
magnitude) to use for opacity mapping have also been provided.

This option is available when using the "Projected tetra" or "Resample to Image" volume rendering modes for unstructured grids and when using the "Smart" and "GPU Based" volume rendering modes for regular grids (image data, uniform grids, and rectilinear grids).
