GLLOGICOP() GLLOGICOP() 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 be- tween 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 dis- able 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 in- dex mode. The initial value is disabled for both operations. +------------------+-----------------+ | 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 | +------------------+-----------------+ opcode is a symbolic constant chosen from the list above. In the explana- tion 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 ap- plied independently to each bit pair of the source and destination indices or colors. NOTES Color index logical operations are always supported. RGBA logical opera- tions 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, logi- cal 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 exe- cution of glBegin and the corresponding execution 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, glBlendFunc, glDrawBuffer, glEnable, glStencilOp GLLOGICOP()
NAME | C SPECIFICATION | PARAMETERS | DESCRIPTION | NOTES | ERRORS | ASSOCIATED GETS | SEE ALSO
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