2003-2004 Silicon Graphics, Inc.
glLogicOp 3G
glLogicOp specify a logical pixel operation

## 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 color and the color at the corresponding location in the frame buffer. To enable or disable the logical operation, call glEnable and glDisable with argument `GL_COLOR_LOGIC_OP`. Logical operation is initially 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 indices or colors.

## Errors

`GL_INVALID_ENUM` is generated if opcode is not an accepted value.

## See Also

glAlphaFunc, glBlendFunc, glEnable, glStencilOp

## Copyright

Copyright 2003-2004 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.