underlay Subroutine

Purpose

Sets the number of user-defined bitplanes used for underlay drawing.

Libraries

Graphics Library

C (libgl.a)

FORTRAN (libfgl.a)

C Syntax

void underlay(Int32 planes)

FORTRAN Syntax

SUBROUTINE UNDERL(planes)
INTEGER*4 planes

Description

The underlay subroutine sets the number of user-defined bitplanes used for underlay colors to 0, 2, or 4, depending on the adapter. The underlay color appears whenever all the bits in the color bitplanes are 0 (zero). The system has either two or four bitplanes that can be allocated as either underlay or overlay. Call the underlay subroutine to set them as underlay bitplanes.

The High-Performance 8-bit 3-D Color Graphics Processor can be configured with either 0 or 2 underlay planes. The 8-bit adapter has a total of 2 auxiliary planes, which can be configured into 2/0 or 0/2 overlay/underlay. For example, setting the number of underlay planes to 2 forces the number of overlay planes to 0.

The High-Performance 24-bit 3-D Color Graphics Processor can be configured with either 0, 2, or 4 underlay planes. The 24-bit adapter has a total of 4 auxiliary planes, which can be configured into 4/0, 2/2, or 0/4 overlay/underlay. For example, setting the number of underlay planes to 4 forces the number of overlay planes to 0.

Call the gconfig subroutine after the underlay subroutine to activate the underlay setting.

When the drawing mode is UNDERDRAW, all drawing occurs in the underlay bitplanes. In UNDERDRAW mode, FLAT is the only available shading model.

Notes:

1. The operation of this subroutine for the Supergraphics Processor Subsystem is modified. (See Understanding the Adapter.)
2. This subroutine cannot be used to add to a display list.

Parameter

Implementation Specifics

This subroutine is part of GL in the AIXwindows Environment/6000 Version 1, Release 2 with AIXwindows/3D Feature.

Only the Color Graphics Processor has underlay planes.

The POWERgraphics GXT1000 does not support the underlay subroutine.

Files

Related Information

Specifying the target frame buffer for drawing subroutines with the drawmode subroutine.

Reconfiguring the system with the gconfig subroutine.

Setting the number of bitplanes used for overlay colors with the overlay subroutine.

Configuring the Frame Buffer, and Writemasks and Logical Operations.