GLLOGICOP(3G) UNIX Programmer's Manual GLLOGICOP(3G)
NAME
glLogicOp - specify a logical pixel operation for color
index 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 color index or RGBA color
and the color index or RGBA color at the corresponding loca-
tion in the frame buffer. To enable or disable the logical
operation, call glEnable and glDisable using the symbolic
constant GL_COLOR_LOGIC_OP for RGBA mode or
GL_INDEX_LOGIC_OP for color index mode. The initial value is
disabled for both operations.
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Opcode Resulting Operation
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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
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opcode is a symbolic constant chosen from the list above. In
the explanation of the logical operations, s represents the
incoming color index and d represents the index in the frame
MirBSD #10-current Printed 2021-12-07 1
GLLOGICOP(3G) UNIX Programmer's Manual GLLOGICOP(3G)
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.
NOTES
Color index logical operations are always supported. RGBA
logical operations are supported only if the GL version is
1.1 or greater.
When more than one RGBA color or index 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).
ERRORS
GL_INVALID_ENUM is generated if opcode is not an accepted
value.
GL_INVALID_OPERATION is generated if glLogicOp is executed
between the execution of glBegin and the corresponding exe-
cution of glEnd.
ASSOCIATED GETS
glGet with argument GL_LOGIC_OP_MODE.
glIsEnabled with argument GL_COLOR_LOGIC_OP or
GL_INDEX_LOGIC_OP.
SEE ALSO
glAlphaFunc(3G), glBlendFunc(3G), glDrawBuffer(3G),
glEnable(3G), glStencilOp(3G)
MirBSD #10-current Printed 2021-12-07 2