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.


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.


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.


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.


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


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.


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.


is a value in a three-dimensional array.