1GLSTENCILOP(3G) [FIXME: manual] GLSTENCILOP(3G)
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6 glStencilOp - set front and back stencil test actions
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9 void glStencilOp(GLenum sfail, GLenum dpfail, GLenum dppass);
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12 sfail
13 Specifies the action to take when the stencil test fails. Eight
14 symbolic constants are accepted: GL_KEEP, GL_ZERO, GL_REPLACE,
15 GL_INCR, GL_INCR_WRAP, GL_DECR, GL_DECR_WRAP, and GL_INVERT. The
16 initial value is GL_KEEP.
17 dpfail
19 Specifies the stencil action when the stencil test passes, but the
20 depth test fails. dpfail accepts the same symbolic constants as
21 sfail. The initial value is GL_KEEP.
22 dppass
24 Specifies the stencil action when both the stencil test and the
25 depth test pass, or when the stencil test passes and either there
26 is no depth buffer or depth testing is not enabled. dppass accepts
27 the same symbolic constants as sfail. The initial value is GL_KEEP.
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30 Stenciling, like depth-buffering, enables and disables drawing on a
31 per-pixel basis. You draw into the stencil planes using GL drawing
32 primitives, then render geometry and images, using the stencil planes
33 to mask out portions of the screen. Stenciling is typically used in
34 multipass rendering algorithms to achieve special effects, such as
35 decals, outlining, and constructive solid geometry rendering.
36 The stencil test conditionally eliminates a pixel based on the outcome
38 of a comparison between the value in the stencil buffer and a reference
39 value. To enable and disable the test, call glEnable() and
40 glDisable with argument GL_STENCIL_TEST; to control it, call
42 glStencilFunc() or glStencilFuncSeparate().
43 There can be two separate sets of sfail, dpfail, and dppass parameters;
45 one affects back-facing polygons, and the other affects front-facing
46 polygons as well as other non-polygon primitives. glStencilOp() sets
47 both front and back stencil state to the same values. Use
48 glStencilOpSeparate() to set front and back stencil state to different
49 values.
50 glStencilOp takes three arguments that indicate what happens to the
52 stored stencil value while stenciling is enabled. If the stencil test
53 fails, no change is made to the pixel's color or depth buffers, and
54 sfail specifies what happens to the stencil buffer contents. The
55 following eight actions are possible.
56 GL_KEEP
58 Keeps the current value.
59 GL_ZERO
61 Sets the stencil buffer value to 0.
62 GL_REPLACE
64 Sets the stencil buffer value to ref, as specified by
65 glStencilFunc().
66 GL_INCR
68 Increments the current stencil buffer value. Clamps to the maximum
69 representable unsigned value.
70 GL_INCR_WRAP
72 Increments the current stencil buffer value. Wraps stencil buffer
73 value to zero when incrementing the maximum representable unsigned
74 value.
75 GL_DECR
77 Decrements the current stencil buffer value. Clamps to 0.
78 GL_DECR_WRAP
80 Decrements the current stencil buffer value. Wraps stencil buffer
81 value to the maximum representable unsigned value when decrementing
82 a stencil buffer value of zero.
83 GL_INVERT
85 Bitwise inverts the current stencil buffer value.
86 Stencil buffer values are treated as unsigned integers. When
88 incremented and decremented, values are clamped to 0 and 2 n - 1, where
89 n is the value returned by querying GL_STENCIL_BITS.
90 The other two arguments to glStencilOp specify stencil buffer actions
92 that depend on whether subsequent depth buffer tests succeed (dppass)
93 or fail (dpfail) (see glDepthFunc()). The actions are specified using
94 the same eight symbolic constants as sfail. Note that dpfail is ignored
95 when there is no depth buffer, or when the depth buffer is not enabled.
96 In these cases, sfail and dppass specify stencil action when the
97 stencil test fails and passes, respectively.
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100 Initially the stencil test is disabled. If there is no stencil buffer,
101 no stencil modification can occur and it is as if the stencil tests
102 always pass, regardless of any call to glStencilOp.
103 glStencilOp() is the same as calling glStencilOpSeparate() with face
105 set to GL_FRONT_AND_BACK.
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108 GL_INVALID_ENUM is generated if sfail, dpfail, or dppass is any value
109 other than the defined constant values.
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112 glGet() with argument GL_STENCIL_FAIL, GL_STENCIL_PASS_DEPTH_PASS,
113 GL_STENCIL_PASS_DEPTH_FAIL, GL_STENCIL_BACK_FAIL,
114 GL_STENCIL_BACK_PASS_DEPTH_PASS, GL_STENCIL_BACK_PASS_DEPTH_FAIL, or
115 GL_STENCIL_BITS
116 glIsEnabled() with argument GL_STENCIL_TEST
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120 ┌────────────┬───────────────────────────────────────────────────────────────────────┐
121 │ │ OpenGL Version │
122 ├────────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┤
123 │Function │ 2.0 │ 2.1 │ 3.0 │ 3.1 │ 3.2 │ 3.3 │ 4.0 │ 4.1 │ 4.2 │ 4.3 │ 4.4 │ 4.5 │
124 │/ │ │ │ │ │ │ │ │ │ │ │ │ │
125 │Feature │ │ │ │ │ │ │ │ │ │ │ │ │
126 │Name │ │ │ │ │ │ │ │ │ │ │ │ │
127 ├────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
128 │glStencilOp │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │
129 └────────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┘
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132 glBlendFunc(), glDepthFunc(), glEnable(), glLogicOp(), glStencilFunc(),
133 glStencilFuncSeparate(), glStencilMask(), glStencilMaskSeparate(),
134 glStencilOpSeparate()
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137 Copyright © 1991-2006 Silicon Graphics, Inc. Copyright © 2010-2014
138 Khronos Group. This document is licensed under the SGI Free Software B
139 License. For details, see http://oss.sgi.com/projects/FreeB/.
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142 Copyright © 1991-2006 Silicon Graphics, Inc.
143 Copyright © 2010-2014 Khronos Group
144[FIXME: source] 07/13/2018 GLSTENCILOP(3G)