An interactive computer graphics display system processing method for identifying a displayed primitive that intersects an operator selected area of the display screen. Pursuant to the method, the operator selected area of the display screen is reverse mapped to world coordinate space; data representative of displayed geometric primitives is then clipped against the reverse mapped selected area in world coordinate space; and clipped data representative of displayed geometric primitives that intersect the reverse mapped selected area are identified for operator defined application processing. Further processing steps include mapping of the identified data to screen coordinate space and rasterization of the data for display in the screen monitor. A zoom processing method is also provided wherein an original operator defined zoom window is transformed from screen coordinate space to world coordinate space and the boundaries of the transformed window in world coordinate space are utilized as data clipping boundaries. After clipping, data representative of a displayed geometric primitive outside the inverse mapped zoom window is discarded, thus preventing the rerasterization of geometric primitives outside the zoom window. Further processing includes mapping of the identified data to a defined zoom window in screen coordinate space for operator viewing and selection of a particular geometric primitive for application processing.