GLLOGICOP(3G) OpenGL Manual GLLOGICOP(3G)
NAME
glLogicOp - specify a logical pixel operation for rendering
C SPECIFICATION
void glLogicOp(GLenum opcode);
PARAMETERS
opcode
Specifies a symbolic constant that selects a logical operation. The following symbols are accepted: GL_CLEAR, GL_SET, GL_COPY,
GL_COPY_INVERTED, GL_NOOP, GL_INVERT, GL_AND, GL_NAND, GL_OR, GL_NOR, GL_XOR, GL_EQUIV, GL_AND_REVERSE, GL_AND_INVERTED, GL_OR_REVERSE,
and GL_OR_INVERTED. The initial value is GL_COPY.
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 glEnable() and glDisable() using the symbolic
constant GL_COLOR_LOGIC_OP. The initial value is disabled.
+-------------------------------+---------------------------------------------+
| | |
| Opcode | Resulting Operation |
| | |
+-------------------------------+---------------------------------------------+
|GL_CLEAR | 0 |
+-------------------------------+---------------------------------------------+
|GL_SET | 1 |
+-------------------------------+---------------------------------------------+
|GL_COPY | s |
+-------------------------------+---------------------------------------------+
|GL_COPY_INVERTED | ~s |
+-------------------------------+---------------------------------------------+
|GL_NOOP | d |
+-------------------------------+---------------------------------------------+
|GL_INVERT | ~d |
+-------------------------------+---------------------------------------------+
|GL_AND | s & d |
+-------------------------------+---------------------------------------------+
|GL_NAND | ~(s & d) |
+-------------------------------+---------------------------------------------+
|GL_OR | s | d |
+-------------------------------+---------------------------------------------+
|GL_NOR | ~(s | d) |
+-------------------------------+---------------------------------------------+
|GL_XOR | s ^ d |
+-------------------------------+---------------------------------------------+
|GL_EQUIV | ~(s ^ d) |
+-------------------------------+---------------------------------------------+
|GL_AND_REVERSE | s & ~d |
+-------------------------------+---------------------------------------------+
|GL_AND_INVERTED | ~s & d |
+-------------------------------+---------------------------------------------+
|GL_OR_REVERSE | s | ~d |
+-------------------------------+---------------------------------------------+
|GL_OR_INVERTED | ~s | 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.
NOTES
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 glDrawBuffer()).
Logic operations have no effect on floating point draw buffers. However, if GL_COLOR_LOGIC_OP is enabled, blending is still disabled in
this case.
ERRORS
GL_INVALID_ENUM is generated if opcode is not an accepted value.
ASSOCIATED GETS
glGet() with argument GL_LOGIC_OP_MODE.
glIsEnabled() with argument GL_COLOR_LOGIC_OP.
SEE ALSO
glBlendFunc(), glDrawBuffer(), glEnable(), glStencilOp()
COPYRIGHT
Copyright (C) 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/.
AUTHORS
opengl.org
opengl.org 06/10/2014 GLLOGICOP(3G)