GPSAC - Set Surface Approximation Criteria

Purpose

Use GPSAC to insert a Set Surface Approximation Criteria structure element into the open structure following the element pointer or to replace the element pointed at by the element pointer with a Set Surface Approximation Criteria structure element depending on the current edit mode.

This structure element determines how the graPHIGS API tessellates subsequent surfaces during structure traversal. Tessellation divides the surfaces into a set of line and/or area geometries for subsequent processing.

Depending on the criteria selected, the graPHIGS API uses only the control values or uses the control values in conjunction with the tessellation vectors in the surface definition to determine how surfaces are tessellated.

The traversal default for surface approximation criteria is 1=WORKSTATION_DEPENDENT with the u control value (ctrlval1) and v control value (ctrlval2) parameter values both set to 1.0.

If the workstation does not support the specified criteria, then the criteria defaults to 1=WORKSTATION_DEPENDENT , with ctrlval1 and ctrlval2 values both set to 1.0.

For information on surface tessellation and on how surface approximation criteria is applied, see The graPHIGS Programming Interface: Understanding Concepts

Parameters