Abstract: A hardware filter for controlling the detectability, highlighting and invisibility of graphics primitives. Each of the three display attributes (detectability, highlighting, and invisibility) being controlled has associated with it both an inclusion counter and an exclusion counter, for a total of six counters. Associated with each class name is a flag, indicating whether the class name is a member of the currently active set, as well as a 6-bit string indicating the effect of the class on each of the six filters. On traversal of the structure hierarchy, upon encountering an order for the addition of a class name to the set, and if the flag corresponding to the class name has not already been set, the flag is set and the corresponding filter counters are incremented in parallel by gating an incrementing signal with the 6-bit string.

Abstract: A graphics display system picking function tracks machine states of pickable primitive operators through the use of a pick stack and machine state memory. The pick stack operates as a stack when accessed by pipeline processors. Pipeline processors can add an element to the stack or remove elements from the stack as structures are processed. Selection or picking of an object causes a graphics control processor to randomly access the pick stack to determine the attributes of a picked primitive. The machine state memory is implemented as a video RAM allowing rapid copying of rows containing machine states for various structure levels in the hierarchy. A first area of the machine state memory stores the states relating to the structures in the hierarchy as they are executed. A second area retains an abbreviated state description for each pickable primitive while a final area contains abbreviated machine state information for picked objects to be echoed by the system.

Abstract: A multi-processor graphics system including a general purpose system control processor for setting up the workstation environment and data traversal structures based upon an application model language description. Workload balancing and interprocessor communication is managed by defining a general purpose interface between the general purpose processor and special purpose graphics control processor. The system control processor accepts application program information in a standard form, such as a hierarchical graphics language definition, then converts it into generalized interface control blocks for communication to the graphics control processor. Graphics control processor is signalled by an interrupt from the system control processor to begin the traversal process. The graphics control processor can then access the standard control blocks contained in system memory and perform the traversal necessary to generate the requested graphics image.