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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.

       ┌───────────────────────────────┬───────────────────────────────────┐
       │                               │                                   │
       │                        OpcodeResulting │
       │                               │ 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 © 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