Name

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.

OpcodeResulting Operation
GL_CLEAR0
GL_SET1
GL_COPYs
GL_COPY_INVERTED ~s
GL_NOOPd
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/.