开启服务器端的opengl功能
void glEnable( GLenum cap);
GL_BLEND
If enabled, blend the computed fragment color values with the values in the color buffers. See glBlendFunc.
GL_CLIP_DISTANCE i
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 −wc≤zc≤wc
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.
开启深度测试，默认深度测试是关闭的，也就是深度缓冲区不会写入内存（和写不写入内存没有关系，只是决定是否要进行深度比较）
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 2n−1
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, primitives are discarded after the optional transform feedback stage, but before rasterization. Furthermore, when enabled, glClear, glClearBufferData, glClearBufferSubData, glClearTexImage, and glClearTexSubImage are 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 gl_PointSize and clamped to the implementation-dependent point size range.
GL_TEXTURE_2D
3.2版本以后不再有此功能
GL_TEXTURE_2D
