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 parameter of eglChooseConfig and eglCreatePbufferSurface, and by the parameter of eglGetConfigAttrib EGL_DEPTH_ENCODING_NV 0x30E2 Accepted as a value in the parameter of eglChooseConfig and eglCreatePbufferSurface, and returned in the 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.