Hewlett-packard Company

Autodesk, Inc.

Kells A Elmquist

John R Wallace

Eric A Haines

David Wayne Arsenault

Kent M Montgomery

Samir L Hanna

Louise M Watson

An approach for incrementally updating graphical images when using anti-aliasing techniques is disclosed. Data for an original color is stored, and an image is filtered based on the original color. A new color for an image portion less than the entire image is identified. The new color is used with the old color to re-filter the image portion. The re-filtering may be performed by a two-step approach in which the image portion is filtered using the negative of the original color and then the image portion is filtered using the new color. The re-filtering may be performed by a one-step approach in which the portion of the image is filtered using the difference between the new color and the old color. The appearance of a halo around the portion of the image that would otherwise occur when filtering based on only the new color is thereby avoided.

Incremental update of graphical images when using anti-aliasing techniques

A method for rendering a three-dimensional image on a computer graphics display device involving the steps of providing a data base defining at least the geometry and reflectivity of light emitters and object in the scene and approximating surfaces of each object in the scene as patches in three dimensional space. Each patch is approximated as one or more elements defined by vertices. A source of irradiated light in the scene is selected and defined as a light source. Then, for each vertex, a form factor representing the fraction of light energy that arrives at the vertex from the source is determined by ray tracing from the vertex to the source. Radiosity is then determined at each vertex based on the form factors determined for each vertex. This process is repeated a selected number of times using a different light source each time. In this manner a plurality of radiosities are determined that collectively indicate the global illumination of the scene. The scene is then displayed based upon these radiosities.

Three dimensional computer graphics employing ray tracing to compute

Shadow testing of a two dimensional projection of a three dimensional scene is accelerated by superimposing the projection with a plurality of scan areas, then examining points, and edges of objects, falling within each scan area. Points are identified as potentially shadowed points if bracketed by edges of any object, and the bracketing object is identified as a potential shadower of the potentially shadowed points. Potential shadowers and potentially shadowed points undergo a series of tests to rapidly determine which, if any, of the potential shadowers are actual shadowers of each potentially shadowed point.

Accelerated shadow testing method for three dimensional graphics

A method for employing a hierarchical display list in global rendering comprises the steps of traversing the display list and extracting selected primitives and attributes. A bounding volume is defined for selected primitives, and data indicative of the selected primitives, attributes, and bounding volumes are stored in a global database. Global rendering may be performed by either ray tracing or radiosity based upon the data in the global database. In the event that global rendering is performed by radiosity, then a plurality of surface elements for each selected primitive is defined and also stored in the global data base. Shading attribute data for each of the surface elements is defined upon application of a radiosity rendering algorithm to the global database. An alternative display list may be defined from the global database, if desired.

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Lansing, NY, United States of America

Kells A Elmquist