GlEnable

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_glEnable: enable or disable server-side GL capabilities


Syntax

 SUB _glEnable (BYVAL cap AS _UNSIGNED LONG)
 void _glEnable(GLenum cap);
 SUB _glDisable (BYVAL cap AS _UNSIGNED LONG)
 void _glDisable(GLenum cap);


cap
Specifies a symbolic constant indicating a GL capability.


Syntax

| name = glEnablei, glDisablei | core = 3.0 }}

 void _glEnablei(GLenum cap, GLuint index);
 void _glDisablei(GLenum cap, GLuint index);
cap
Specifies a symbolic constant indicating a GL capability.
index
Specifies the index of the capability to enable/disable.


Description

_glEnable and _glDisable enable and disable various capabilities. Use _glIsEnabled or _glGet to determine the current setting of any capability. The initial value for each capability with the exception of _GL_DITHER and _GL_MULTISAMPLE is _GL_FALSE. The initial value for _GL_DITHER and _GL_MULTISAMPLE is _GL_TRUE.

Both _glEnable and _glDisable take a single argument, cap, which can assume one of the following values:

_GL_BLEND
If enabled, blend the computed fragment color values with the values in the color buffers. See glBlendFunc. Sets the blend enable/disable flag for all color buffers.
_GL_CLIP_DISTANCEi
If enabled, clip geometry against user-defined half space i.
_GL_COLOR_LOGIC_OP
If enabled, apply the currently selected logical operation to the computed fragment color and color buffer values. See glLogicOp.
_GL_CULL_FACE
If enabled, cull polygons based on their winding in window coordinates. See glCullFace.
_GL_DEBUG_OUTPUT
If enabled, debug messages are produced by a debug context. When disabled, the debug message log is silenced. Note that in a non-debug context, very few, if any messages might be produced, even when _GL_DEBUG_OUTPUT is enabled.
_GL_DEBUG_OUTPUT_SYNCHRONOUS
If enabled, debug messages are produced synchronously by a debug context. If disabled, debug messages may be produced asynchronously. In particular, they may be delayed relative to the execution of GL commands, and the debug callback function may be called from a thread other than that in which the commands are executed. See _glDebugMessageCallback.
_GL_DEPTH_CLAMP
If enabled, the -w<sub>c</sub> &le; z<sub>c</sub> &le; w<sub>c</sub> plane equation is ignored by view volume clipping (effectively, there is no near or far plane clipping). See glDepthRange.
_GL_DEPTH_TEST
If enabled, do depth comparisons and update the depth buffer. Note that even if the depth buffer exists and the depth mask is non-zero, the depth buffer is not updated if the depth test is disabled. See glDepthFunc and glDepthRange.
_GL_DITHER
If enabled, dither color components or indices before they are written to the color buffer.
_GL_FRAMEBUFFER_SRGB
If enabled and the value of _GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING for the framebuffer attachment corresponding to the destination buffer is _GL_SRGB, the R, G, and B destination color values (after conversion from fixed-point to floating-point) are considered to be encoded for the sRGB color space and hence are linearized prior to their use in blending.
_GL_LINE_SMOOTH
If enabled, draw lines with correct filtering. Otherwise, draw aliased lines. See glLineWidth.
_GL_MULTISAMPLE
If enabled, use multiple fragment samples in computing the final color of a pixel. See glSampleCoverage.
_GL_POLYGON_OFFSET_FILL
If enabled, and if the polygon is rendered in _GL_FILL mode, an offset is added to depth values of a polygon's fragments before the depth comparison is performed. See glPolygonOffset.
_GL_POLYGON_OFFSET_LINE
If enabled, and if the polygon is rendered in _GL_LINE mode, an offset is added to depth values of a polygon's fragments before the depth comparison is performed. See glPolygonOffset.
_GL_POLYGON_OFFSET_POINT
If enabled, an offset is added to depth values of a polygon's fragments before the depth comparison is performed, if the polygon is rendered in _GL_POINT mode. See glPolygonOffset.
_GL_POLYGON_SMOOTH
If enabled, draw polygons with proper filtering. Otherwise, draw aliased polygons. For correct antialiased polygons, an alpha buffer is needed and the polygons must be sorted front to back.
_GL_PRIMITIVE_RESTART
Enables primitive restarting. If enabled, any one of the draw commands which transfers a set of generic attribute array elements to the GL will restart the primitive when the index of the vertex is equal to the primitive restart index. See _glPrimitiveRestartIndex.
_GL_PRIMITIVE_RESTART_FIXED_INDEX
Enables primitive restarting with a fixed index. If enabled, any one of the draw commands which transfers a set of generic attribute array elements to the GL will restart the primitive when the index of the vertex is equal to the fixed primitive index for the specified index type. The fixed index is equal to <math>2^n - 1</math> where n is equal to 8 for _GL_UNSIGNED_BYTE, 16 for _GL_UNSIGNED_SHORT and 32 for _GL_UNSIGNED_INT.
_GL_RASTERIZER_DISCARD
If enabled, all primitives are discarded before rasterization, but after any optional transform feedback. Also causes _glClear and _glClearBuffer commands to be ignored.
_GL_SAMPLE_ALPHA_TO_COVERAGE
If enabled, compute a temporary coverage value where each bit is determined by the alpha value at the corresponding sample location. The temporary coverage value is then ANDed with the fragment coverage value.
_GL_SAMPLE_ALPHA_TO_ONE
If enabled, each sample alpha value is replaced by the maximum representable alpha value.
_GL_SAMPLE_COVERAGE
If enabled, the fragment's coverage is ANDed with the temporary coverage value. If _GL_SAMPLE_COVERAGE_INVERT is set to _GL_TRUE, invert the coverage value. See glSampleCoverage.
_GL_SAMPLE_SHADING
If enabled, the active fragment shader is run once for each covered sample, or at fraction of this rate as determined by the current value of _GL_MIN_SAMPLE_SHADING_VALUE. See glMinSampleShading.
_GL_SAMPLE_MASK
If enabled, the sample coverage mask generated for a fragment during rasterization will be ANDed with the value of _GL_SAMPLE_MASK_VALUE before shading occurs. See glSampleMaski.
_GL_SCISSOR_TEST
If enabled, discard fragments that are outside the scissor rectangle. See glScissor.
_GL_STENCIL_TEST
If enabled, do stencil testing and update the stencil buffer. See glStencilFunc and glStencilOp.
_GL_TEXTURE_CUBE_MAP_SEAMLESS
If enabled, cubemap textures are sampled such that when linearly sampling from the border between two adjacent faces, texels from both faces are used to generate the final sample value. When disabled, texels from only a single face are used to construct the final sample value.
_GL_PROGRAM_POINT_SIZE
If enabled and a vertex or geometry shader is active, then the derived point size is taken from the (potentially clipped) shader builtin Template:Code and clamped to the implementation-dependent point size range.

Indexed Capabilities

Some of the GL's capabilities are indexed. _glEnablei and _glDisablei enable and disable indexed capabilities. Only the following capabilities may be used with indices higher than zero:

_GL_BLEND
If enabled, blend the computed fragment color values with the values in the specified color buffer. index must be less than _GL_MAX_DRAW_BUFFERS or _GL_INVALID_VALUE will result. See glBlendFunc.


Errors

_GL_INVALID_ENUM is generated if cap is not one of the values listed previously.

_GL_INVALID_VALUE is generated by _glEnablei and _glDisablei if index is greater than or equal to the number of indexed capabilities for cap.


Notes:

_GL_PRIMITIVE_RESTART is available only if the GL version is 3.1 or greater.

_GL_TEXTURE_CUBE_MAP_SEAMLESS is available only if the GL version is 3.2 or greater.

_GL_PRIMITIVE_RESTART_FIXED_INDEX is available only if the GL version is 4.3 or greater.

_GL_DEBUG_OUTPUT and _GL_DEBUG_OUTPUT_SYNCHRONOUS are available only if the GL version is 4.3 or greater.

Any token accepted by _glEnable or _glDisable is also accepted by _glEnablei and _glDisablei, but if the capability is not indexed, the maximum value that index may take is zero.

In general, passing an indexed capability to _glEnable or _glDisable will enable or disable that capability for all indices, resepectively.


Use With:

_glIsEnabled

_glGet


See also

SUB _GL _glActiveTexture, _glBlendFunc, _glCullFace, _glDepthFunc, _glDepthRange, _glGet, _glIsEnabled, _glLineWidth, _glLogicOp, _glPointSize, _glPolygonMode, _glPolygonOffset, _glSampleCoverage, _glScissor, _glStencilFunc, _glStencilOp, _glTexImage1D, _glTexImage2D, _glTexImage3D


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/.



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Copyright 1991-2006 Silicon Graphics, Inc. Copyright 2010-2011 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.