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+Name
+
+ NV_depth_nonlinear
+
+Name Strings
+
+ GL_NV_depth_nonlinear
+ EGL_NV_depth_nonlinear
+
+Contact
+
+ Gary King, NVIDIA Corporation (gking 'at' nvidia.com)
+
+Notice
+
+ Copyright NVIDIA Corporation, 2005 - 2007.
+
+Status
+
+ NVIDIA Proprietary
+
+Version
+
+ Last Modified: 2007/03/20
+ NVIDIA Revision: 1.0
+
+Number
+
+ EGL Extension #18
+ OpenGL ES Extension #73
+
+Dependencies
+
+ Written based on the wording of the OpenGL 2.0 Specification and
+ EGL 1.2 Specification.
+
+ Requires EGL 1.1.
+
+ Requires OpenGL-ES 1.0.
+
+ OES_framebuffer_object affects the wording of this specification.
+
+Overview
+
+ Due to the perspective divide, conventional integer Z-buffers have
+ a hyperbolic distribution of encodings between the near plane
+ and the far plane. This can result in inaccurate depth testing,
+ particularly when the number of depth buffer bits is small
+ and objects are rendered near the far plane.
+
+ Particularly when the number of depth buffer bits is limited
+ (desirable and/or required in low-memory environments), artifacts
+ due to this loss of precision may occur even with relatively
+ modest far plane-to-near plane ratios (e.g., greater than 100:1).
+
+ Many attempts have been made to provide alternate encodings for
+ Z-buffer (or alternate formulations for the stored depth) to
+ reduce the artifacts caused by perspective division, such as
+ W-buffers, Z-complement buffers and floating-point 1-Z buffers.
+
+ This extension adds a non-linear encoded Z buffer to OpenGL,
+ which can improve the practically useful range of, e.g. 16-bit
+ depth buffers by up to a factor of 16, greatly improving depth
+ test quality in applications where the ratio between the near
+ and far planes can not be as tightly controlled.
+
+IP Status
+
+ NVIDIA Proprietary
+
+New Procedures and Functions
+
+ None
+
+New Tokens
+
+ Accepted as a valid sized internal format by all functions accepting
+ sized internal formats with a base format of DEPTH_COMPONENT
+
+ DEPTH_COMPONENT16_NONLINEAR_NV 0x8E2C
+
+ Accepted by the <attrib_list> parameter of eglChooseConfig and
+ eglCreatePbufferSurface, and by the <attribute> parameter of
+ eglGetConfigAttrib
+
+ EGL_DEPTH_ENCODING_NV 0x30E2
+
+ Accepted as a value in the <attrib_list> parameter of eglChooseConfig
+ and eglCreatePbufferSurface, and returned in the <value> parameter
+ of eglGetConfigAttrib
+
+ EGL_DEPTH_ENCODING_NONE_NV 0
+ EGL_DEPTH_ENCODING_NONLINEAR_NV 0x30E3
+
+Changes to the OpenGL 2.0 Specification
+
+ Add the following line to table 3.16 (p. 154)
+
+ +--------------------------------+-----------------+------+
+ | Sized Internal Format | Base Internal | D |
+ | | Format | Bits |
+ +--------------------------------+-----------------+------+
+ | DEPTH_COMPONENT16_NONLINEAR_NV | DEPTH_COMPONENT | 16 |
+ +--------------------------------+-----------------+------+
+
+Changes to the EGL 1.2 Specification
+
+ Add the following line to table 3.1 (p. 14)
+
+ +--------------------------+------+---------------------------------------+
+ | Attribute | Type | Notes |
+ +--------------------------+------+---------------------------------------+
+ | EGL_DEPTH_ENCODING_NV | enum | Type of depth-buffer encoding employed|
+ +--------------------------+------+---------------------------------------+
+
+ Modify the description of the depth buffer in Section 3.4 (p. 15)
+
+ "The depth buffer is used only by OpenGL ES. It contains fragment depth
+ (Z) information generated during rasterization. EGL_DEPTH_SIZE indicates
+ the depth of this buffer in bits, and EGL_DEPTH_ENCODING_NV indicates which
+ alternate depth-buffer encoding (if any) should be used. Legal values for
+ EGL_DEPTH_ENCODING_NV are: EGL_DONT_CARE, EGL_DEPTH_ENCODING_NONE_NV and
+ EGL_DEPTH_ENCODING_NONLINEAR_NV."
+
+ Add the following line to table 3.4 (p. 20)
+
+ +-----------------------+---------------+-----------+-------+----------+
+ | Attribute | Default | Selection | Sort | Sort |
+ | | | Criteria | Order | Priority |
+ +-----------------------+---------------+-----------+-------+----------+
+ | EGL_DEPTH_ENCODING_NV | EGL_DONT_CARE | Exact | None | - |
+ +-----------------------+---------------+-------------------+----------+
+
+Issues
+
+ None
+
+Revision History
+
+#1.0 - 20.03.2007
+
+ Renumbered enumerants. Reformatted to 80 columns.