Abstract: A method for traversal of primitives in a graphics display system includes calculating pick data for a predetermined primitive, testing the primitive for invisibility, exiting to a next graphics order if the invisibility step is positive, testing the primitive for detectability, exiting to a next graphics order if the detectability test is false when traversal is performed for pick correlation purposes, determining whether a transformation environment update is required, recalculating the transformation environment if required, binding display attributes for the primitive and processing subsequent graphics orders to draw the primitive. Also, to eliminate unnecessary storing of registers when an execute structure is processed, a number of registers are set aside for storing control flags to selectively store registers into the stack. If a flag pick is zero the contents of the corresponding register will be stored on the stack.

Abstract: In graphics display systems the use of matrix concatenation for coordinate transformation, occasionally, will cause an overflow which may represent an out-of-bounds location of a data element. To correct the overflow problem, a number of translation shift factors are introduced for the last row of the matrix which when used to operate on matrix elements, will maintain the elements within the physical boundaries of the graphics base by preventing overflow. Additionally, a method of adjusting the clipping boundaries to increase the precision of coordinate transformations is also described. The methods of the invention may be implemented in microcode in a commercially availably graphics display system such as the IBM 5080 Graphics System.