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GL3.2 for AIX: Graphics Library (GL) Technical Reference

zwritemask Subroutine

Purpose

Specifies the z-buffer writemask.

Libraries

Graphics Library

C (libgl.a)

FORTRAN (libfgl.a)

C Syntax

void zwritemask(Int32 mask)

FORTRAN Syntax

SUBROUTINE ZWRITE(mask)
INTEGER*4 mask

Description

The zwritemask subroutine specifies a write-enable mask on the z-buffer. If a bit in the mask is set (1), the corresponding bitplane is enabled for reading and writing, and any subroutine that updates the z-buffer can update that bitplane. If a bit in the mask is reset (0), the corresponding bitplane is marked as read-only, and the values stored in that bitplane are not updated.

Parameter

mask Specifies the mask indicating which z-buffer bits are read only and which can be overwritten. The following rules apply:
If a bit of the mask is set to 0, the corresponding bits are read-only.
If a bit of the mask is set to 1, the corresponding z-buffer bits can be overwritten.

Implementation Specifics

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

On the 3-D Color Graphics Processor, the z-buffer writemask is ignored when drawing is performed directly into the z-buffer; that is, when the value of the zdraw subroutine is True. Instead, the color-planes writemask is applied.

The 3-D Color Graphics Processor, and the Supergraphics Processor Subsystem, and the POWER GXT1000 adapter support only two values for the z-buffer writemask: 0x000000 and 0xffffff. All other values are ignored.

The POWER Gt4 and POWER Gt4x adapters support a z-buffer writemask in banks of 8 bitplanes. The eight supported values for the writemask are 0x000000, 0x0000ff, 0x00ff00, 0xff0000, 0x00ffff, 0xffff00, 0xff00ff, and 0xffffff. All other values are ignored.

If an unsupported writemask is specified with this subroutine, it is ignored, and the current writemask is not changed.

Files

/usr/include/gl/gl.h Contains C language constant and variable type definitions for GL.
/usr/include/gl/fgl.h Contains FORTRAN constant and variable type definitions for GL.

Related Information

Granting write access to a subset of available bitplanes with the RGBwritemask subroutine.

Enabling drawing to the z-buffer with the zdraw subroutine.

Specifying an RGBA writemask with a single, packed integer with the wmpack subroutine.

Granting write permission to available bitplanes with the writemask subroutine.

AIX Graphics Library Overview, Writemasks and Logical Operations, and Removing Hidden Surfaces.


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