NAME
glLogicOp
- specify a logical pixel operation for color index rendering
C SPECIFICATION
void ggllLLooggiiccOOpp(
GLenum _o_p_c_o_d_e )
PARAMETERS
-
_o_p_c_o_d_e
-
Specifies a symbolic constant that selects a logical operation.
The following symbols are accepted:
GGLL__CCLLEEAARR,
GGLL__SSEETT,
GGLL__CCOOPPYY,
GGLL__CCOOPPYY__IINNVVEERRTTEEDD,
GGLL__NNOOOOPP,
GGLL__IINNVVEERRTT,
GGLL__AANNDD,
GGLL__NNAANNDD,
GGLL__OORR,
GGLL__NNOORR,
GGLL__XXOORR,
GGLL__EEQQUUIIVV,
GGLL__AANNDD__RREEVVEERRSSEE,
GGLL__AANNDD__IINNVVEERRTTEEDD,
GGLL__OORR__RREEVVEERRSSEE, and
GGLL__OORR__IINNVVEERRTTEEDD. The initial value is GGLL__CCOOPPYY.
DESCRIPTION
ggllLLooggiiccOOpp 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 location in the
frame buffer.
To enable or disable the logical operation, call
ggllEEnnaabbllee and ggllDDiissaabbllee
using the symbolic constant GGLL__CCOOLLOORR__LLOOGGIICC__OOPP for RGBA mode or
GGLL__IINNDDEEXX__LLOOGGIICC__OOPP for color index mode. The initial value is
disabled for both operations.
center;
lb lb
l c.
_
Opcode Resulting Operation
_
GGLL__CCLLEEAARR 0
GGLL__SSEETT 1
GGLL__CCOOPPYY s
GGLL__CCOOPPYY__IINNVVEERRTTEEDD ~s
GGLL__NNOOOOPP d
GGLL__IINNVVEERRTT ~d
GGLL__AANNDD s & d
GGLL__NNAANNDD ~(s & d)
GGLL__OORR s | d
GGLL__NNOORR ~(s | d)
GGLL__XXOORR s ^ d
GGLL__EEQQUUIIVV ~(s ^ d)
GGLL__AANNDD__RREEVVEERRSSEE s & ~d
GGLL__AANNDD__IINNVVEERRTTEEDD ~s & d
GGLL__OORR__RREEVVEERRSSEE s | ~d
GGLL__OORR__IINNVVEERRTTEEDD ~s | d
_
_o_p_c_o_d_e 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 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 ggllDDrraawwBBuuffffeerr).
ERRORS
GGLL__IINNVVAALLIIDD__EENNUUMM is generated if _o_p_c_o_d_e is not an accepted value.
GGLL__IINNVVAALLIIDD__OOPPEERRAATTIIOONN is generated if ggllLLooggiiccOOpp
is executed between the execution of ggllBBeeggiinn
and the corresponding execution of ggllEEnndd.
ASSOCIATED GETS
ggllGGeett with argument GGLL__LLOOGGIICC__OOPP__MMOODDEE.
ggllIIssEEnnaabblleedd with argument GGLL__CCOOLLOORR__LLOOGGIICC__OOPP or GGLL__IINNDDEEXX__LLOOGGIICC__OOPP.
SEE ALSO
ggllAAllpphhaaFFuunncc((33GG)),
ggllBBlleennddFFuunncc((33GG)),
ggllDDrraawwBBuuffffeerr((33GG)),
ggllEEnnaabbllee((33GG)),
ggllSStteenncciillOOpp((33GG))