Abstract: An item buffer is used to determine which graphic object has been picked by a user. A graphics object list is traversed to display each graphic object and assign a unique item identifier to each. For each pixel location in each of the graphic objects, the unique item identifier is stored at a corresponding location in the item buffer. A graphics object is selected using a pointer device, and the pointer device location is used to access the item buffer and retrieve the item identifier that defines the graphic object picked. If a pixel location in the item buffer is not large enough to hold the complete item identifier, the item identifier is partially constructed in each of several passes, and the pass data combined in main memory.

Abstract: An item buffer is used to determine which graphic object has been picked by a user. A graphics object list is traversed to display each graphic object and assign a unique item identifier to each. For each pixel location in each of the graphic objects, the unique item identifier is stored at a corresponding location in the item buffer. A graphics object is selected using a pointer device, and the pointer device location is used to access the item buffer and retrieve the item identifier that defines the graphic object picked. If a pixel location in the item buffer is not large enough to hold the complete item identifier, the item identifier is partially constructed in each of several passes, and the pass data combined in main memory.

Abstract: 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.