GlLogicOp
_glLogicOp: specify a logical pixel operation for rendering
Syntax
SUB _glLogicOp (BYVAL opcode AS _UNSIGNED LONG) void _glLogicOp(GLenum opcode);
- opcode
- Specifies a symbolic constant that selects a logical operation. The following symbols are accepted: Template:KW, Template:KW, Template:KW, Template:KW, Template:KW, Template:KW, Template:KW, Template:KW, Template:KW, Template:KW, Template:KW, Template:KW, Template:KW, Template:KW, Template:KW, and Template:KW. The initial value is Template:KW.
Description
_glLogicOp specifies a logical operation that, when enabled, is applied between the incoming RGBA color and the RGBA color at the corresponding location in the frame buffer. To enable or disable the logical operation, call Template:KW and Template:KW using the symbolic constant Template:KW. The initial value is disabled.
| Opcode | Resulting Operation |
|---|---|
| Template:KW | 0 |
| Template:KW | 1 |
| Template:KW | s |
| Template:KW | ~s |
| Template:KW | d |
| Template:KW | ~d |
| Template:KW | s & d |
| Template:KW | ~(s & d) |
| Template:KW | d |
| Template:KW | d) |
| Template:KW | s ^ d |
| Template:KW | ~(s ^ d) |
| Template:KW | s & ~d |
| Template:KW | ~s & d |
| Template:KW | ~d |
| Template:KW | d |
opcode is a symbolic constant chosen from the list above. In the explanation of the logical operations, s represents the incoming color and d represents the color in the frame buffer. Standard C-language operators are used. As these bitwise operators suggest, the logical operation is applied independently to each bit pair of the source and destination colors.
When more than one RGBA color buffer is enabled for drawing, logical operations are performed separately for each enabled buffer, using for the destination value the contents of that buffer (see Template:KW).
Logic operations have no effect on floating point draw buffers. However, if Template:KW is enabled, blending is still disabled in this case.
Template:KW is generated if opcode is not an accepted value.
Template:KW with argument Template:KW.
Template:KW with argument Template:KW.
See also
SUB _GL Template:KW, Template:KW, Template:KW, Template:KW
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/.