GPTCAC - Set Trimming Curve Approximation Criteria

Purpose

Use GPTCAC to insert a Set Trimming Curve 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 Trimming Curve Approximation Criteria structure element depending on the current edit mode.

This structure element enables the application to control the tessellation of the trimming curve as well as the surface in the area of the curve when rendering subsequent trimmed surface primitives during structure traversal.

Depending on the criteria selected, the graPHIGS API only uses the control values or uses the control values in conjunction with the tessellation vector in the trimmed surface primitive definition to determine how the trimming curve is tessellated.

The traversal default for trimming curve approximation criteria is 1=WORKSTATION_DEPENDENT with the control value (ctrlval1), the u control value (ctrlval2), and v control value (ctrlval3) all set to a value of 1.0.

If the workstation does not support the specified trimming curve approximation criteria, then the default trimming curve criteria is 1=WORKSTATION_DEPENDENT with ctrlval1, ctrlval2, and ctrlval3 all set to a value of 1.0.

For information on trimmed surfaces and how trimming curve approximation criteria is applied, see The graPHIGS Programming Interface: Understanding Concepts

Parameters