glLogicOp
[New
- Windows 95, OEM Service Release 2]
The glLogicOp
function specifies a logical pixel operation for color index rendering.
void glLogicOp(
|
GLenum opcode |
|
|
); |
|
Parameters
opcode
A symbolic
constant that selects a logical operation. The following symbols are accepted:
|
Opcode |
Resulting
Value |
|
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 |
Remarks
The glLogicOp
function specifies a logical operation that, when enabled, is applied between
the incoming color index and the color index at the corresponding location in
the frame buffer. The logical operation is enabled or disabled with glEnable and glDisable using
the symbolic constant GL_LOGIC_OP.
The opcode
parameter is a symbolic constant chosen from the list below. 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 indexes.
Logical pixel
operations are not applied to RGBA color buffers.
When more
than one color-index buffer is enabled for drawing, logical operations are done
separately for each enabled buffer, using the contents of that buffer for the
destination index (see glDrawBuffer).
The opcode
parameter must be one of the 16 accepted values. Other values result in an
error.
The following
functions retrieve information related to glLogicOp:
glGet
with argument GL_LOGIC_OP_MODE
glIsEnabled with argument GL_LOGIC_OP
Error Codes
The following
are the error codes generated and their conditions.
|
Error
Code |
Condition |
|
GL_INVALID_ENUM
|
opcode was not an accepted value. |
|
GL_INVALID_OPERATION
|
glLogicOp was called between a call to glBegin and the
corresponding call to glEnd. |
See Also