GLAPI/glLogicOp: Difference between revisions

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; opcode
; opcode
: Specifies a symbolic constant that selects a logical operation. The following symbols are accepted: {{code|GL_CLEAR}}, {{code|GL_SET}}, {{code|GL_COPY}}, {{code|GL_COPY_INVERTED}}, {{code|GL_NOOP}}, {{code|GL_INVERT}}, {{code|GL_AND}}, {{code|GL_NAND}}, {{code|GL_OR}}, {{code|GL_NOR}}, {{code|GL_XOR}}, {{code|GL_EQUIV}}, {{code|GL_AND_REVERSE}}, {{code|GL_AND_INVERTED}}, {{code|GL_OR_REVERSE}}, and {{code|GL_OR_INVERTED}}. The initial value is {{code|GL_COPY}}.
: Specifies a symbolic constant that selects a logical operation. The following symbols are accepted: {{enum|GL_CLEAR}}, {{enum|GL_SET}}, {{enum|GL_COPY}}, {{enum|GL_COPY_INVERTED}}, {{enum|GL_NOOP}}, {{enum|GL_INVERT}}, {{enum|GL_AND}}, {{enum|GL_NAND}}, {{enum|GL_OR}}, {{enum|GL_NOR}}, {{enum|GL_XOR}}, {{enum|GL_EQUIV}}, {{enum|GL_AND_REVERSE}}, {{enum|GL_AND_INVERTED}}, {{enum|GL_OR_REVERSE}}, and {{enum|GL_OR_INVERTED}}. The initial value is {{enum|GL_COPY}}.


== Description ==
== Description ==


'''glLogicOp''' specifies a logical operation that, when enabled, is applied between the incoming RGBA color and the RGBA color at the corresponding location in the frame buffer. To enable or disable the logical operation, call {{apifunc|glEnable}} and {{apifunc|glDisable}} using the symbolic constant {{code|GL_COLOR_LOGIC_OP}}. The initial value is disabled.
'''glLogicOp''' specifies a logical operation that, when enabled, is applied between the incoming RGBA color and the RGBA color at the corresponding location in the frame buffer. To enable or disable the logical operation, call {{apifunc|glEnable}} and {{apifunc|glDisable}} using the symbolic constant {{enum|GL_COLOR_LOGIC_OP}}. The initial value is disabled.






{|
{|
|+
|-
! '''Opcode'''
! '''Opcode'''
! '''Resulting Operation'''
! '''Resulting Operation'''
|+
|-
| {{code|GL_CLEAR}}
| {{enum|GL_CLEAR}}
| 0
| 0
|+
|-
| {{code|GL_SET}}
| {{enum|GL_SET}}
| 1
| 1
|+
|-
| {{code|GL_COPY}}
| {{enum|GL_COPY}}
| s
| s
|+
|-
| {{code|GL_COPY_INVERTED}}
| {{enum|GL_COPY_INVERTED}}
| ~s
| ~s
|+
|-
| {{code|GL_NOOP}}
| {{enum|GL_NOOP}}
| d
| d
|+
|-
| {{code|GL_INVERT}}
| {{enum|GL_INVERT}}
| ~d
| ~d
|+
|-
| {{code|GL_AND}}
| {{enum|GL_AND}}
| s & d
| s & d
|+
|-
| {{code|GL_NAND}}
| {{enum|GL_NAND}}
| ~(s & d)
| ~(s & d)
|+
|-
| {{code|GL_OR}}
| {{enum|GL_OR}}
| s | d
| s | d
|+
|-
| {{code|GL_NOR}}
| {{enum|GL_NOR}}
| ~(s | d)
| ~(s | d)
|+
|-
| {{code|GL_XOR}}
| {{enum|GL_XOR}}
| s ^ d
| s ^ d
|+
|-
| {{code|GL_EQUIV}}
| {{enum|GL_EQUIV}}
| ~(s ^ d)
| ~(s ^ d)
|+
|-
| {{code|GL_AND_REVERSE}}
| {{enum|GL_AND_REVERSE}}
| s & ~d
| s & ~d
|+
|-
| {{code|GL_AND_INVERTED}}
| {{enum|GL_AND_INVERTED}}
| ~s & d
| ~s & d
|+
|-
| {{code|GL_OR_REVERSE}}
| {{enum|GL_OR_REVERSE}}
| s | ~d
| s | ~d
|+
|-
| {{code|GL_OR_INVERTED}}
| {{enum|GL_OR_INVERTED}}
| ~s | d
| ~s | d
|}
|}
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When more than one RGBA color 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 {{apifunc|glDrawBuffer}}).
When more than one RGBA color 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 {{apifunc|glDrawBuffer}}).


Logic operations have no effect on floating point draw buffers. However, if {{code|GL_COLOR_LOGIC_OP}} is enabled, blending is still disabled in this case.
Logic operations have no effect on floating point draw buffers. However, if {{enum|GL_COLOR_LOGIC_OP}} is enabled, blending is still disabled in this case.


== Errors ==
== Errors ==


{{code|GL_INVALID_ENUM}} is generated if {{param|opcode}} is not an accepted value.
{{enum|GL_INVALID_ENUM}} is generated if {{param|opcode}} is not an accepted value.


== Associated Gets ==
== Associated Gets ==


{{apifunc|glGet}} with argument {{code|GL_LOGIC_OP_MODE}}.
{{apifunc|glGet}} with argument {{enum|GL_LOGIC_OP_MODE}}.


{{apifunc|glIsEnabled}} with argument {{code|GL_COLOR_LOGIC_OP}}.
{{apifunc|glIsEnabled}} with argument {{enum|GL_COLOR_LOGIC_OP}}.


== See Also ==
== See Also ==


{{apifunc|glBlendFunc}}, {{apifunc|glDrawBuffer}}, {{apifunc|glEnable}}, {{apifunc|glStencilOp}}
{{apifunc|glEnable|(GL_COLOR_LOGIC_OP)}}, {{apifunc|glDrawBuffer}}, {{apifunc|glDrawBuffers}}, {{apifunc|glStencilOp}}


== Copyright ==
== Copyright ==


Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see [http://oss.sgi.com/projects/FreeB/ http://oss.sgi.com/projects/FreeB/].
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see [https://khronos.org/registry/OpenGL-Refpages/LICENSES/LicenseRef-FreeB.txt LicenseRef-FreeB].


[[Category:Core API Ref Post Fragment Shader Operations|LogicOp]]
[[Category:Core API Ref Post Fragment Shader Operations|LogicOp]]
[[Category:Core API Reference|LogicOp]]
[[Category:Core API Reference|LogicOp]]

Latest revision as of 22:05, 5 February 2021

glLogicOp
Core in version 4.6
Core since version 1.0

glLogicOp: specify a logical pixel operation for rendering

Function Definition

 void glLogicOp(GLenum opcode​);
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 between the incoming RGBA color and the 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. The initial value is disabled.


Opcode Resulting Operation
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 d
GL_NOR d)
GL_XOR s ^ d
GL_EQUIV ~(s ^ d)
GL_AND_REVERSE s & ~d
GL_AND_INVERTED ~s & d
GL_OR_REVERSE ~d
GL_OR_INVERTED d

opcode​ is a symbolic constant chosen from the list above. In the explanation of the logical operations, s represents the incoming color and d represents the color 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 colors.

Notes

When more than one RGBA color 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 glDrawBuffer).

Logic operations have no effect on floating point draw buffers. However, if GL_COLOR_LOGIC_OP is enabled, blending is still disabled in this case.

Errors

GL_INVALID_ENUM is generated if opcode​ is not an accepted value.

Associated Gets

glGet with argument GL_LOGIC_OP_MODE.

glIsEnabled with argument GL_COLOR_LOGIC_OP.

See Also

glEnable(GL_COLOR_LOGIC_OP), glDrawBuffer, glDrawBuffers, glStencilOp

Copyright

Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see LicenseRef-FreeB.

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