- brick
is a set of voxels that is small enough to be cached by underlying hardware, generally texture memory.

- brick set
is composed of one or more adjacent bricks.

- brick set collection
is one or more brick sets for applications and platforms that require several copies of the same volume with possibly different memory layouts, for example, XY, XZ, and YZ stacks of slices.

- caching
maintains objects in anticipation for future reuse; transient geometry can be cached from frame to frame in order to amortize polygonization cost.

- clip box
is an abstract construct associated with overlapping bricks. If two bricks overlap, all geometry, for example, sampling surfaces, has to be clipped to each brick's clip box to avoid seaming.

- data type
is voxel's numeric representation, for example, unsigned byte, or float.

- external format
is an application side voxel format, for example, INTENSITY.

- faces
are polygons resulting from polygonization. Each face is a slice of a volume and may consist of a number of polygons.

- internal format
is a voxel format internal to the graphics adaptor, for example, INTENSITY8_EXT.

- model (or shape)
is a combination of geometry and appearance attributes; for example a triangle with per-vertex color, or a tetrahedron with 3D textures mapped on it; it is the graphical object that appears in the scene.

- multi-planar reformation
is a cross section through a volume

- native (or disk) format
is a format of the voxels as they are store on the disk, for example, INTENSITY.

- polygonization
is the process of slicing a volumetric geometry along with a family of surfaces. The result is a set of polygons, each with a different texture. These polygons are used to display the volume and can be passed to other rendering toolkits, such as IRIS Performer.

- ray casting
In this approach, a ray is traversed from the viewer's eye trough each drawable pixel with colors and opacities accumulated along the way. Can proceed in ray-order or sampling-distance order.

- slicing
is a process of sampling of a solid model with a family of surfaces in order to polygonize it. Sampling-distance order ray casting.

- tessellation
subdividing a shape into primitives. For example, a concave polygon can be tessellated into triangles, a solid torus into tetrahedra.

- transient geometry
is face sets resulting from polygonizations; these are often discarded after each frame.

- volume
is a pair of geometry and appearance defining a volumetric model.

- volume roaming
displaying an interactively manipulated volume of interest that is substantially smaller than the whole volume.

- volumetric (or solid) model
is defined as the combination of geometry (for example, a sphere) and appearance (for example, the voxels representing your data) to represent a solid (i.e., not hollow) object.

- volumetric primitive
is a building block used in modeling of solid shapes. For example: tetrahedron, prism, pyramid, hexahedron, cylinder, cone, sphere; primitives are used to build more complex shapes, for example, sub-parts of a volume, region of interest, or a deformable grid.

- voxel coordinates
is a reference frame for specifying per-vertex properties, for example, T3F refers to voxel reference frame. Voxel coordinates map piecewise linearly onto the per-brick texture coordinates.

- voxel
is a value in a three-dimensional array.