# Method GL.glLogicOp()

Method glLogicOp

  ``void` glLogicOp(`int` `opcode`)`

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 location 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.

  .ne .TS center box ; ci | ci c | c . 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 .TE

  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 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.

Parameter `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.

Throws

  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 execution of glEnd.