In many applications it is desirable to give different visual properties to different parts of the volume, often based on the results of segmentation or image processing algorithms. Examples include: where identified organs or vessels are colored differently, or for two-dimensional opacity tables.

The 3mensio SDK™ offers a very flexible solution by controlling the visual properties via a mask volume. A mask volume has the same dimensions as the data volume but only requires 8 bits per voxel. Each voxel of the mask volume can therefore hold an identifier between 0 and 255 and identifies which component or segment of the corresponding voxel in the data volume it belongs to.

Instead of providing a single opacity curve for the data volume, you can provide up to 256 opacity curves, all with different colors and opacities. During rendering, the mask volume is used to determine which opacity curve is applied to which voxels.