glLogicOp
- specify a logical pixel operation
void glLogicOp(GLenum opcode)
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
.
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.
GL_INVALID_ENUM
is generated if opcode
is not an accepted value.
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/.