glLogicOp

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.

QuickInfo

  Windows NT: Use version 3.5 and later.
  Windows: Use Windows 95 and later.
  Windows CE: Unsupported.
  Header: Declared in gl.h.
  Import Library: Link with opengl32.lib.

See Also

glAlphaFunc, glBegin, glBlendFunc, glDrawBuffer, glEnable, glEnd, glIsEnabled, glStencilOp