[karxxm]

Most volume renderers lack a good transfer function editor. When analyzing volumes, especially explorative analysis, the most effective tool is to dial in colors and opacities for certain value ranges, in order to find structures.

The volume rendering engine I have been working on uses a histogram for the value distribution, and on top of it, one can draw lines that indicate the opacity. Additionally, one can set colors to the control points, which are then linearly interpolated for the given ranges.