Abstract: An apparatus illuminates samples in a volume rendering pipeline. The apparatus includes the following units. A gradient magnitude modulation unit produces an opacity, emissive, diffuse and specular modulation factor from a gradient magnitude vector of each sample. A reflectance mapping unit produces a diffuse intensity and a specular intensity from the gradient magnitude vector of each sample and an eye vector of the volume. A first arithmetic logic unit combines an opacity of each sample with the corresponding opacity modulation factor to generate modulated opacities. A second arithmetic logic unit combines an emissive coefficient with the emissive modulation factor of each sample to generate modulated emissive coefficients. A third arithmetic logic unit combines the diffuse intensity with the diffuse modulation factor of each sample to generate modulated diffuse intensities.

Abstract: A volume rendering processor renders a two-dimensional image from a volume data set of voxels constituting a three-dimensional representation of an object. Voxel memory interface logic retrieves the voxels from a voxel memory in a scanned order with respect to X, Y and Z coordinate axes, the Z axis being the axis most nearly parallel to a predefined viewing direction. The set of voxels having equal Z coordinate values are referred to as a “slice” of voxels. Interpolation logic calculates a sequence of samples from the retrieved voxels such that (i) each sample lies along a corresponding imaginary ray extending through the object parallel to the viewing direction, (ii) each sample results from interpolating the eight voxels surrounding the sample in the XYZ coordinate system. “Supersampling” in the Z dimension is performed such that the number of samples calculated for each ray is greater than the number of slices of voxels in the volume data set.

Abstract: A method renders a volume data set including a plurality of voxels. In the method, a). the volume data set is apportioned into a plurality of sections. Then, b). a first one of the plurality of sections is rendered by sequentially reading groups of voxels from an external memory and rendering the groups of voxels in the section. Then, c). any accumulated data from the rendering of the first one of the plurality of sections is stored in a temporary storage device. Then, a next one of the plurality of sections is rendered by sequentially reading groups of voxels of the next one of the plurality of sections from an external memory and rendering the groups of voxels, the rendering incorporating accumulated data from the temporary storage device, and then any accumulated data from the rendering of the next one of the plurality of sections is stored in the temporary storage device. Steps d and e are repeated until each of the plurality of sections of the volume data set have been rendered.

Abstract: An apparatus renders a volume data set including a plurality of voxels stored in a voxel memory. The apparatus includes a plurality of pipelines operating in parallel. Each pipeline includes a buffer storing at least one block of at least two voxels of the volume data set. An interpolation stage reads the at least one block of at least two voxels from the buffer. A gradient estimation stage receives an output from the interpolation stage. A compositing stage receives an output from the gradient estimation stage. The apparatus also includes a plurality of interface devices, wherein each interface device couples a particular stage only to an adjacent identical stage in a neighboring pipeline so that identical stages of the pipelines are connected in a ring.

Abstract: A volume graphics device renders a volume data set. The volume data set is apportioned into blocks of volume data, and each of the blocks are apportioned into a plurality of mini-blocks, each mini-block includes at least two voxels of volume data. The volume graphics device includes memory apportioned into a plurality of portions, wherein neighboring blocks of the volume data set are each stored in different ones of the plurality of portions of the memory, and wherein the mini-blocks of each block are stored in consecutive locations in the portion of memory associated with the associated block.

Abstract: A volume rendering processor establishes a cut-plane region of a volume data set, the cut-plane region being defined by a plane equation and minimum and maximum distance values representing the values of the plane equation at outer faces of the cut-plane region. The plane equation is evaluated for each sample of the volume data, the result is compared with the minimum and maximum distance values to determine whether the sample is in the cut-plane region, and the visibility of the sample is adjusted depending on the comparison result. The plane equation is evaluated by continually accumulating the coefficient values in an order indicated by the ordering of the sequence of samples.

Abstract: Apparatus is provided to enable real-time volume rendering on a personal computer or a desktop computer in which a technique involving blocking of voxel data organizes the data so that all voxels within a block are stored at consecutive memory addresses within a single memory model, making possible fetching an entire block of data in a burst rather than one voxel at a time. This permits utilization of DRAM memory modules which provide high capacity and low cost with substantial space savings. Additional techniques including sectioning reduces the amount of intermediate storage in a processing pipeline to an acceptable level for semiconductor implementation. A multiplexing technique takes advantage of blocking to reduce the amount of data needed to be transmitted per block, thus reducing the number of pins and the rates at which data must be transmitted across the pins connecting adjacent processing modules with each other.

Abstract: A system generates and arranges images depicting volume data using opacity nd color transfer functions for review and selection by a user. In volume rendering, an opacity and/or color transfer function is applied to three-dimensional scalar field data. The transfer functions have different characteristics represented as input parameters, such as control points of the function. The input parameters are then processed to determine images of the volumes and corresponding output vectors. The output vectors can be pixels in the images, or other characteristics of interest. The input vectors are selected to provide a dispersed set of output vectors. A large number of random input vectors can be generated and then culled to leave a dispersed set of output vectors. Alternatively, a set of randomly generated input vectors of a predetermined size are randomly perturbed, to further disperse the output vectors. The output vectors are displayed so that positions represent distances between the output vectors.

Abstract: A method and apparatus for providing real-time processing of voxels and real-time volume visualization of objects and scenes in a highly parallel and pipelined manner includes a three dimensional (3-D) skewed memory, two dimensional (2-D) skewed buffers, 3-D interpolation and shading of data points, and signal compositing. The method and apparatus implement ray-casting, a powerful volume rendering technique. Viewing rays are cast from the viewing position into a cubic frame buffer and beams of voxels, which are parallel to the face of the cubic frame buffer, are accessed. At evenly spaced sample points along each viewing ray, each sample point is tri-linearly interpolated using values of surrounding voxels. Central differences of voxels around the sample points yield a gradient which is used as a surface normal approximation. Using the gradient and the interpolated sample values, a local shading model is applied and a sample opacity is assigned.

Abstract: A method and apparatus for providing real-time processing of voxels and real-time volume visualization of objects and scenes in a highly parallel and pipelined manner using a three dimensional (3-D) skewed memory, a modular fast bus, two dimensional (2-D) skewed buffers, 3-D interpolation and shading of data points, and a ray projection cone. The method and apparatus permit investigation and viewing of real-time static (3-D) and dynamic (4-D) high resolution volumetric data sets such as those found in medical imaging, biology, non-destructive quality assurance, scientific visualization, computer aided design (CAD), flight simulation, realistic graphics and the like. The method and apparatus implement ray-casting, a powerful volume rendering technique. Viewing rays are cast from the viewing position into a cubic frame buffer. At evenly spaced sample points along each viewing ray, the data is tri-linearly interpolated using values of surrounding voxels.