GLPOLYGONOFFSET(3G)

NAME
glPolygonOffset - set the scale and units used to calculate depth values

C SPECIFICATION

void glPolygonOffset(GLfloat factor, GLfloat units);

PARAMETERS

factor
    Specifies a scale factor that is used to create a variable depth offset for each polygon. The initial value is 0.

units
    Is multiplied by an implementation-specific value to create a constant depth offset. The initial value is 0.

DESCRIPTION

When GL_POLYGON_OFFSET_FILL, GL_POLYGON_OFFSET_LINE, or GL_POLYGON_OFFSET_POINT is enabled, each fragment's depth value will be offset after it is interpolated from the depth values of the appropriate vertices. The value of the offset is factor × DZ + r × units, where DZ is a measurement of the change in depth relative to the screen area of the polygon, and r is the smallest value that is guaranteed to produce a resolvable offset for a given implementation. The offset is added before the depth test is performed and before the value is written into the depth buffer.

glPolygonOffset is useful for rendering hidden-line images, for applying decals to surfaces, and for rendering solids with highlighted edges.

ASSOCIATED GETS

glIsEnabled() with argument GL_POLYGON_OFFSET_FILL, GL_POLYGON_OFFSET_LINE, or GL_POLYGON_OFFSET_POINT.

glGet() with argument GL_POLYGON_OFFSET_FACTOR or GL_POLYGON_OFFSET_UNITS.

SEE ALSO

glDepthFunc(), glEnable(), glGet(), glIsEnabled()

COPYRIGHT

Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.