glpolygonoffset(3g) [redhat man page]

GLPOLYGONOFFSET(3G)													       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.

NOTES

       glPolygonOffset is available only if the GL version is 1.1 or greater.

       glPolygonOffset has no effect on depth coordinates placed in the feedback buffer.

       glPolygonOffset has no effect on selection.

ERRORS

       GL_INVALID_OPERATION is generated if glPolygonOffset is executed between the execution of glBegin and the corresponding execution of glEnd.

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(3G), glEnable(3G), glGet(3G), glIsEnabled(3G)

															       GLPOLYGONOFFSET(3G)

GLDEPTHFUNC(3G) 														   GLDEPTHFUNC(3G)

NAME

       glDepthFunc - specify the value used for depth buffer comparisons

C SPECIFICATION

       void glDepthFunc( GLenum func )

PARAMETERS

       func  Specifies	the  depth  comparison	function.   Symbolic  constants  GL_NEVER,  GL_LESS, GL_EQUAL, GL_LEQUAL, GL_GREATER, GL_NOTEQUAL,
	     GL_GEQUAL, and GL_ALWAYS are accepted.  The initial value is GL_LESS.

DESCRIPTION

       glDepthFunc specifies the function used to compare each incoming pixel depth value with the depth value present in the depth  buffer.   The
       comparison is performed only if depth testing is enabled.  (See glEnable and glDisable of GL_DEPTH_TEST.)

       func specifies the conditions under which the pixel will be drawn.  The comparison functions are as follows:

       GL_NEVER        Never passes.

       GL_LESS	       Passes if the incoming depth value is less than the stored depth value.

       GL_EQUAL        Passes if the incoming depth value is equal to the stored depth value.

       GL_LEQUAL       Passes if the incoming depth value is less than or equal to the stored depth value.

       GL_GREATER      Passes if the incoming depth value is greater than the stored depth value.

       GL_NOTEQUAL     Passes if the incoming depth value is not equal to the stored depth value.

       GL_GEQUAL       Passes if the incoming depth value is greater than or equal to the stored depth value.

       GL_ALWAYS       Always passes.

       The  initial  value  of func is GL_LESS.  Initially, depth testing is disabled.	Even if the depth buffer exists and the depth mask is non-
       zero, the depth buffer is not updated if the depth test is disabled.

ERRORS

       GL_INVALID_ENUM is generated if func is not an accepted value.

       GL_INVALID_OPERATION is generated if glDepthFunc is executed between the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS

       glGet with argument GL_DEPTH_FUNC
       glIsEnabled with argument GL_DEPTH_TEST

SEE ALSO

       glDepthRange(3G), glEnable(3G), glPolygonOffset(3G)

																   GLDEPTHFUNC(3G)