graPHIGS Programming Interface: Subroutine Reference

The graPHIGS Programming Interface : Subroutine Reference

GPBTCO - Set Back Transparency Coefficient

GPBTCO (coeff)

Purpose

Use GPBTCO to insert a Set Back Transparency Coefficient structure element into the open structure following the element pointer, or to replace the element pointed at by the element pointer with a Set Back Transparency Coefficient structure element, depending upon the current edit mode.

During traversal, the value of coeff specifies the source transparency coefficient of subsequent back facing portions of area primitives. The graPHIGS API uses the specified coefficient if the face distinguish mode (GPFDMO) is set to 2=COLOR_SURFACE_PROPERTIES The use of the transparency coefficient depends on the Transparency Processing Mode of the view table entry.

The current back transparency coefficient in the graPHIGS API Traversal State List is also set by the back transparency coefficient of the Set Back Surface Properties (GPBSPR) subroutine.

The traversal default for the back transparency coefficient value is 0.0.

Parameters

coeff -- specified by user, short floating-point number

Back transparency coefficient (0.0<=coeff<=1.0).

Error Codes

5: FUNCTION REQUIRES STATE STOP OR NROP (NOT STCL)
115: TRANSPARENT COEFFICIENT IS INVALID

Related Subroutines

GPBSPR: Set Back Surface Properties
GPFDMO: Set Face Distinguish Mode
GPSPR: Set Surface Properties
GPTCO: Set Transparency Coefficient

RCP code

201343506 (X'0C004212')