Name NV_render_depth_texture Name Strings WGL_NV_render_depth_texture Contact Pat Brown, NVIDIA Corporation (pbrown 'at' nvidia.com) Notice Copyright NVIDIA Corporation, 2001, 2002. Status Shipping, March 2002. Version Last Modified Date: 2003/01/08 NVIDIA Revision: 1 Number 263 Dependencies OpenGL 1.1 is required. ARB_render_texture is required. SGIX_depth_texture is required. NV_render_texture_rectangle affects the definition of this extension. Overview This extension allows a depth buffer to be used for both rendering and texturing. It is built upon the ARB_render_texture extension; the only addition in this extension is the ability to use a depth buffer as a DEPTH_COMPONENT texture map. Issues In the ARB_render_texture spec, the number and size of physical depth buffers in a rendered texture is left undefined. From the ARB_render_texture specification: The contents of the depth and stencil buffers may not be preserved when rendering a texture to the pbuffer and switching which image of the texture is rendered to (e.g., switching from rendering one mipmap level to rendering another). That behavior is clearly unacceptable in an implementation where the rendered texture IS the depth buffer. RESOLVED: Yes, it needs to be fixed. This extension specifies that each mipmap level and cube map face gets its own depth buffer, whose contents are preserved when switching render targets. Should there be separate pixel format attributes for BIND_TO_TEXTURE_DEPTH and BIND_TO_TEXTURE_RECTANGLE_DEPTH? Or is a single attribute sufficient? RESOLVED: We should support separate capabilities, as done with the other formats. See the NV_render_texture_rectangle spec for more info. Should it be possible to have a single pbuffer support binding both color and depth buffers to textures? RESOLVED: Yes. This means that we must provide a separate DEPTH_TEXTURE_FORMAT attribute that must be set at pbuffer creation time, since using only the TEXTURE_FORMAT attribute would allow you to create a pbuffer supporting either color or depth textures, but not both. For double-buffered or stereo pixel formats that support binding to depth textures, how many depth buffers do you have? RESOLVED: There is only a single depth buffer for double-buffered or stereo pixel formats. Double buffering refers only to the number of color buffers. There will be multiple depth buffers only if the pbuffer is specified to support mipmaps or cube maps. What happens with multisample pixel formats, where the only depth buffer contains multiple samples per pixel? This issue is slightly different for rendered depth textures, since multisample pixel formats do contain "normal" color buffers in addition to the multisample buffer. UNRESOLVED. New Procedures and Functions None. New Tokens Accepted by the parameter of wglGetPixelFormatAttribivARB, wglGetPixelFormatAttribfvARB, and the and parameters of wglChoosePixelFormatARB: WGL_BIND_TO_TEXTURE_DEPTH_NV 0x20A3 WGL_BIND_TO_TEXTURE_RECTANGLE_DEPTH_NV 0x20A4 Accepted by the parameter of wglCreatePbufferARB and by the parameter of wglQueryPbufferARB: WGL_DEPTH_TEXTURE_FORMAT_NV 0x20A5 Accepted as a value in the parameter of wglCreatePbufferARB and returned in the value parameter of wglQueryPbufferARB when is WGL_DEPTH_TEXTURE_FORMAT_NV: WGL_TEXTURE_DEPTH_COMPONENT_NV 0x20A6 WGL_NO_TEXTURE_ARB 0x2077 Accepted by the parameter of wglBindTexImageARB: WGL_DEPTH_COMPONENT_NV 0x20A7 Additions to Chapter 2 of the OpenGL 1.2.1 Specification (OpenGL Operation) None. Additions to Chapter 3 of the OpenGL 1.2.1 Specification (Rasterization) None. Additions to Chapter 4 of the OpenGL 1.2.1 Specification (Per-Fragment Operations and the Frame Buffer) None. Additions to Chapter 5 of the OpenGL 1.2.1 Specification (Special Functions) None. Additions to Chapter 6 of the OpenGL 1.2.1 Specification (State and State Requests) None. Additions to the WGL Specification First, close your eyes and pretend that a WGL specification actually existed. Maybe if we all concentrate hard enough, one will magically appear. (Add to the description of in wglGetPixelFormatAttribivARB and in wglGetPixelFormatfv:) WGL_BIND_TO_TEXTURE_DEPTH_NV WGL_BIND_TO_TEXTURE_RECTANGLE_DEPTH_NV True if the depth buffer can be bound to a DEPTH_COMPONENT texture or texture rectangle. Currently only pbuffers can be bound as textures so this attribute will only be TRUE if WGL_DRAW_TO_PBUFFER is also TRUE. (Add new table entries to match criteria in description of wglChoosePixelFormatARB:) Attribute Type Match Criteria WGL_BIND_TO_TEXTURE_DEPTH_NV boolean exact WGL_BIND_TO_TEXTURE_RECTANGLE_DEPTH_NV boolean exact (In the wglCreatePbufferARB section, modify the attribute list) WGL_TEXTURE_FORMAT_ARB This attribute indicates the base internal format of the texture that will be created when a color buffer of a pbuffer is bound to a texture map. It can be set to WGL_TEXTURE_RGB_ARB (indicating an internal format of RGB), WGL_TEXTURE_RGBA_ARB (indicating a base internal format of RGBA), or WGL_NO_TEXTURE_ARB. The default value is WGL_NO_TEXTURE_ARB. WGL_DEPTH_TEXTURE_FORMAT_NV This attribute indicates the base internal format of the texture that will be created when the depth buffer of a pbuffer is bound to a texture map. It can be set to WGL_TEXTURE_DEPTH_COMPONENT_NV (indicating an internal format of DEPTH_COMPONENT), or WGL_NO_TEXTURE_ARB. The default value is WGL_NO_TEXTURE_ARB. (In the wglCreatePbufferARB section, modify the discussion of what happens to the depth/stencil/accum buffers when switching between mipmap levels or cube map faces.) For pbuffers with a texture format of WGL_TEXTURE_RGB_ARB or WGL_TEXTURE_RGBA_ARB, there will be a separate set of color buffers for each mipmap level and cube map face in the pbuffer. Otherwise, the WGL implementation is free to share a single set of color, auxillary, and accumulation buffers between levels or faces. For pbuffers with a depth texture format of WGL_TEXTURE_DEPTH_COMPONENT_NV, there will be a separate depth buffer for each mipmap level and cube map face. Otherwise, the WGL implementation is free to share a single depth buffer between levels or faces. The contents of any color or depth buffer that may be shared between faces are undefined after switching between mipmap levels or cube map faces. (In the wglCreatePbufferARB section, add to the error list) ERROR_INVALID_DATA WGL_DEPTH_TEXTURE_FORMAT_NV is WGL_TEXTURE_DEPTH_COMPONENT_NV, WGL_TEXTURE_TARGET_ARB is WGL_TEXTURE_RECTANGLE_NV, and the WGL_BIND_TO_TEXTURE_RECTANGLE_DEPTH_NV attribute is not set in the pixel format. ERROR_INVALID_DATA WGL_DEPTH_TEXTURE_FORMAT_NV is WGL_TEXTURE_DEPTH_COMPONENT_NV, WGL_TEXTURE_TARGET_ARB is not WGL_TEXTURE_RECTANGLE_NV, and the WGL_BIND_TO_TEXTURE_DEPTH_NV attribute is not set in the pixel format. (In the wglCreatePbufferARB section, modify the error list, replacing the errors concerning texture format/target combinations with the following.) ERROR_INVALID_DATA WGL_TEXTURE_TARGET_ARB is WGL_NO_TEXTURE_ARB and either WGL_TEXTURE_FORMAT_ARB or WGL_DEPTH_TEXTURE_FORMAT_NV is not WGL_NO_TEXTURE_ARB. ERROR_INVALID_DATA WGL_TEXTURE_TARGET_ARB is not WGL_NO_TEXTURE_ARB and both WGL_TEXTURE_FORMAT_ARB and WGL_DEPTH_TEXTURE_FORMAT_NV are WGL_NO_TEXTURE_ARB. Modify wglDestroyPbufferARB: A pbuffer is destroyed by calling BOOL wglDestroyPbufferARB(HPBUFFERARB hPbuffer); The pbuffer is destroyed once it is no longer current to any rendering context and once all color and depth buffers that are bound to a texture object have been released. When a pbuffer is destroyed, any memory resources that are attached to it are freed and its handle is no longer valid. .... Modify wglBindTexImageARB: ... The pbuffer attribute WGL_DEPTH_TEXTURE_FORMAT_NV determines the base internal format of the depth texture. The format-specific component sizes are also determined by pbuffer attributes as shown in the table below. The component sizes are dependent on the format of the texture. Texture Component Size Format D WGL_DEPTH_BITS_ARB DEPTH_COMPONENT Table x.x: Size of texture components ... The possible values for are WGL_FRONT_LEFT_ARB, WGL_FRONT_RIGHT_ARB, WGL_BACK_LEFT_ARB, WGL_BACK_RIGHT_ARB, WGL_DEPTH_COMPONENT_NV, and WGL_AUX0_ARB through WGL_AUXn_ARB. ... (Modify paragraphs in wglBindTexImageARB section to include language about allowing depth buffers) Note that the color or depth buffer is bound to a texture object. If the texture object is shared between contexts, then the color or depth buffers are also shared. If a texture object is deleted before wglReleaseTexImageARB is called, then the color buffer is released and the pbuffer is made available for reading and writing. It is not an error to call TexImage2D, TexImage1D, CopyTexImage1D or CopyTexImage2D to replace an image of a texture object that has a color or depth buffer bound to it. However, these calls will cause the color or depth buffers to be released back to the pbuffer and new memory will be allocated for the texture. Note that the color or depth buffer is released even if the image that is being defined is a mipmap level that was not defined by the color buffer. (Modify wglReleaseTexImageARB section to include language allowing the binding of depth buffers) To release a color or depth buffer that is being used as a texture call BOOL wglReleaseTexImageARB (HPBUFFERARB hPbuffer, int iBuffer) This releases the specified color or depth buffer back to the pbuffer. The pbuffer is made available for reading and writing when it no longer has any color or depth buffers bound as textures. must be one of WGL_FRONT_LEFT_ARB, WGL_FRONT_RIGHT_ARB, WGL_BACK_LEFT_ARB, WGL_BACK_RIGHT_ARB, WGL_DEPTH_COMPONENT_NV, or WGL_AUX0_ARB through WGL_AUXn_ARB. The contents of the color or depth buffer being released are undefined when it is first released. In particular, there is no guarantee that the texture image is still present. However, the contents of other color, depth, stencil, or accumulation buffers are unaffected when the color or depth buffer is released. If the specified color or depth buffer is no longer bound to a texture (e.g., because the texture object was deleted) then this call is a noop; no error is generated. After a color or depth buffer is released from a texture (either explicitly by calling wglReleaseTexImageARB or implicitly by calling a routine such as TexImage2D), all texture images that were defined by the color buffer become NULL (it is as if TexImage was called with an image of zero width). New State None Dependencies on NV_render_texture_rectangle If NV_render_texture_rectangle is not supported, all references to texture rectangles and WGL_BIND_TO_TEXTURE_RECTANGLE_DEPTH_NV should be deleted. Revision History None