Wisskirchen, Peter2015-10-052015-10-0519891017-4656https://doi.org/10.2312/egtp.19891030We present a new concept for a graphics system which we call GEO++ . Apart from the manipulation of groups (structures in PHIGS-terminology), GEO++ permits a direct access to the tree structure required for display. With this concept we believe to have achieved a synthesis between the requirements of modelling in the sense of manipulation of building patterns and of display in the sense of editing individual objects (parts) on the screen.10.2312/egtp.19891030