Name EXT_sparse_texture Name Strings GL_EXT_sparse_texture Contributors Dominik Witczak, Mobica Contributors to ARB_sparse_texture Xi Chen, NVIDIA Contact Daniel Koch, NVIDIA Corporation (dkoch 'at' nvidia.com) Notice Copyright (c) 2013 The Khronos Group Inc. Copyright terms at http://www.khronos.org/registry/speccopyright.html Portions Copyright (c) 2014 NVIDIA Corporation. Status Complete. Version Last Modified Date: 27/03/2015 Revision: 3 Number OpenGL ES Extension #240 Dependencies OpenGL ES 3.1 is required. This extension is written against the OpenGL ES 3.1 (June 4, 2014) Specification. This extension interacts with OES_texture_border_clamp. This extension interacts with EXT_texture_border_clamp. This extension interacts with OES_texture_cube_map_array. This extension interacts with EXT_texture_cube_map_array. This extension interacts with OES_texture_view. This extension interacts with EXT_texture_view. This extension interacts with EXT_texture_norm16. The definition of this extension is affected by the presence of EXT_direct_state_access. Overview Recent advances in application complexity and a desire for higher resolutions have pushed texture sizes up considerably. Often, the amount of physical memory available to a graphics processor is a limiting factor in the performance of texture-heavy applications. Once the available physical memory is exhausted, paging may occur bringing performance down considerably - or worse, the application may fail. Nevertheless, the amount of address space available to the graphics processor has increased to the point where many gigabytes - or even terabytes of address space may be usable even though that amount of physical memory is not present. This extension allows the separation of the graphics processor's address space (reservation) from the requirement that all textures must be physically backed (commitment). This exposes a limited form of virtualization for textures. Use cases include sparse (or partially resident) textures, texture paging, on-demand and delayed loading of texture assets and application controlled level of detail. New Procedures and Functions void TexPageCommitmentEXT(enum target, int level, int xoffset, int yoffset, int zoffset, sizei width, sizei height, sizei depth, boolean commit); [[ The following is only added if EXT_direct_state_access is supported. ]] void TexturePageCommitmentEXT(uint texture, int level, int xoffset, int yoffset, int zoffset, sizei width, sizei height, sizei depth, boolean commit); New Tokens Accepted by the parameter to TexParameter{if}{v}, GetTexParameter{if}v, TexParameterI{u}ivOES, GetTexParameterI{u}ivOES TexParameterI{u}ivEXT, and GetTexParameterI{u}ivEXT: TEXTURE_SPARSE_EXT 0x91A6 VIRTUAL_PAGE_SIZE_INDEX_EXT 0x91A7 Accepted by the parameter of GetTexParameter{if}v, GetTexParameterIi{u}vOES, and GetTexParameterIi{u}vEXT: NUM_SPARSE_LEVELS_EXT 0x91AA Accepted by the parameter to GetInternalformativ: NUM_VIRTUAL_PAGE_SIZES_EXT 0x91A8 VIRTUAL_PAGE_SIZE_X_EXT 0x9195 VIRTUAL_PAGE_SIZE_Y_EXT 0x9196 VIRTUAL_PAGE_SIZE_Z_EXT 0x9197 Accepted by the parameter to GetInternalformativ: TEXTURE_2D 0x0DE1 TEXTURE_2D_ARRAY 0x8C1A TEXTURE_CUBE_MAP 0x8513 TEXTURE_CUBE_MAP_ARRAY_OES 0x9009 TEXTURE_3D 0x806F Accepted by the parameter to GetIntegerv, GetFloatv, GetInteger64v, and GetBooleanv: MAX_SPARSE_TEXTURE_SIZE_EXT 0x9198 MAX_SPARSE_3D_TEXTURE_SIZE_EXT 0x9199 MAX_SPARSE_ARRAY_TEXTURE_LAYERS_EXT 0x919A SPARSE_TEXTURE_FULL_ARRAY_CUBE_MIPMAPS_EXT 0x91A9 Additions to Chapter 8 of the OpenGL ES 3.1 Specification (Textures and Samplers) Add the "Supports Sparse Allocation" column to Table 8.13, "Correspondence of sized internal color formats..." +-------------------------------+-------------------------------+ | Sized Internal Format | Supports Sparse Allocation | +-------------------------------+-------------------------------+ | R8 | Y | | R8_SNORM | Y | | R16_EXT | Y | | R16_SNORM_EXT | Y | | RG8 | Y | | RG8_SNORM | Y | | RG16_EXT | Y | | RG16_SNORM_EXT | Y | | RGB565 | Y | | RGB8 | | | RGB8_SNORM | | | RGB16_EXT | | | RGB16_SNORM_EXT | | | RGBA4 | | | RGB5_A1 | | | RGBA8 | Y | | RGBA8_SNORM | Y | | RGB10_A2 | Y | | RGB10_A2UI | Y | | RGBA16_EXT | Y | | RGBA16_SNORM_EXT | Y | | SRGB8 | | | SRGB8_ALPHA8 | | | R16F | Y | | RG16F | Y | | RGB16F | | | RGBA16F | Y | | R32F | Y | | RG32F | Y | | RGB32F | | | RGBA32F | Y | | R11F_G11F_B10F | Y | | RGB9_E5 | Y | | R8I | Y | | R8UI | Y | | R16I | Y | | R16UI | Y | | R32I | Y | | R32UI | Y | | RG8I | Y | | RG8UI | Y | | RG16I | Y | | RG16UI | Y | | RG32I | Y | | RG32UI | Y | | RGB8I | | | RGB8UI | | | RGB16I | | | RGB16UI | | | RGB32I | | | RGB32UI | | | RGBA8I | Y | | RGBA8UI | Y | | RGBA16I | Y | | RGBA16UI | Y | | RGBA32I | Y | | RGBA32UI | Y | +-------------------------------+-------------------------------+ Insert the following paragraph before Table 8.16: If is TEXTURE_SPARSE_EXT or VIRTUAL_PAGE_SIZE_INDEX_EXT, then the state is stored in the texture, but only takes effect the next time storage is allocated for a texture using TexStorage*. If the value of TEXTURE_IMMUTABLE_FORMAT is TRUE, then TEXTURE_SPARSE_EXT and VIRTUAL_PAGE_SIZE_INDEX_EXT cannot be changed and an error is generated. Append to Table 8.20: "Texture parameters and their values." +------------------------------+---------+---------------------------+ | Name | Type | Legal values | +------------------------------+---------+---------------------------+ | TEXTURE_SPARSE_EXT | boolean | TRUE, FALSE | | VIRTUAL_PAGE_SIZE_INDEX_EXT | int | any non-negative integer | +------------------------------+---------+---------------------------+ Add to the Errors table for TexParameter* INVALID_OPERATION is generated if is TEXTURE_SPARSE_EXT or VIRTUAL_PAGE_SIZE_INDEX_EXT and the value of TEXTURE_IMMUTABLE_FORMAT for the texture identified by is TRUE. INVALID_VALUE is generated if is TEXTURE_SPARSE_EXT, is TRUE and is not one of TEXTURE_2D, TEXTURE_2D_ARRAY, TEXTURE_CUBE_MAP, TEXTURE_CUBE_MAP_ARRAY_OES, or TEXTURE_3D. Additions to Section 8.16view (Texture Views), of the OpenGL ES Specification (as added by OES_texture_view or EXT_texture_view): Texture views may be created that reference sparse textures (see Section 8.17sparse.1), and in such cases, the view is considered to be sparse. Should a texture view reference part or all of the tail of a sparse texture, then modifications to the commitment of that tail via the view affect the tail of the parent texture and all other views that reference the tail, even for portions of the tail outside the controlling view. Additions to Section 8.17 of the OpenGL Specification, "Immutable-Format Texture Images" Add the following bullet point to the list of psuedo-operations performed by all variants of TexStorage* (p.188): * If TEXTURE_SPARSE_EXT is TRUE, only virtual address space is allocated for the texture but physical backing store is not. Physical store for pages of a virtual texture may be committed and decommitted by calling TexPageCommitmentEXT. The page size chosen for the texture is taken from the texture's value of VIRTUAL_PAGE_SIZE_INDEX_EXT. In this case, , and must either be integer multiples of the selected virtual page size in the X, Y and Z dimensions, respectively, or be less than those dimensions. Additionally, the dimensions of sparse textures must be compatible with the chosen value of as described in Section 8.17sparse.1. Add to the errors that may be generated by TexStorage*: An INVALID_OPERATION error is generated if the texture's TEXTURE_SPARSE_EXT parameter is TRUE and the value of its VIRTUAL_PAGE_SIZE_INDEX_EXT parameter is greater than or equal to NUM_VIRTUAL_PAGE_SIZES_EXT for the specified target and internal format. An INVALID_VALUE error is generated if the texture's TEXTURE_SPARSE_EXT parameter is TRUE and any of the following are true: * is TEXTURE_3D, and , , or is greater than MAX_SPARSE_3D_TEXTURE_SIZE_EXT; * is not TEXTURE_3D, and or is greater than MAX_SPARSE_TEXTURE_SIZE_EXT; or * is TEXTURE_2D_ARRAY or TEXTURE_CUBE_MAP_ARRAY_OES and is greater than MAX_SPARSE_TEXTURE_ARRAY_LAYERS_EXT. An INVALID_VALUE error is generated if the texture's TEXTURE_SPARSE_EXT parameter is TRUE and or is greater than the value of MAX_SPARSE_3D_TEXTURE_SIZE_EXT when is TEXTURE_3D, or if or is greater than the value of MAX_SPARSE_ARRAY_TEXTURE_LAYERS_EXT if is a 2D array texture target, respectively. An INVALID_VALUE error is generated if TEXTURE_SPARSE_EXT is TRUE and , or is is not an integer multiple of the page size in the corresponding dimension. If the value of SPARSE_TEXTURE_FULL_ARRAY_CUBE_MIPMAPS_EXT is FALSE, then TexStorage* will generate an INVALID_OPERATION error if * the texture's TEXTURE_SPARSE_EXT parameter is TRUE, * is one of TEXTURE_2D_ARRAY, TEXTURE_CUBE_MAP, or TEXTURE_CUBE_MAP_ARRAY_OES, and * for the virtual page size corresponding to the VIRTUAL_PAGE_SIZE_INDEX_EXT parameter, either of the following is true: - is not a multiple of VIRTUAL_PAGE_SIZE_X_EXT * 2^(-1), or - is not a multiple of VIRTUAL_PAGE_SIZE_Y_EXT * 2^(-1). Insert Section 8.17sparse, "Sparse Textures and Commitment" following section 8.17 "Immutable-Format Texture Images". Textures may be allocated such that their images' physical backing store is only partially allocated. Only immutable format textures may be sparsely allocated. To allocate a sparse texture, set a texture's TEXTURE_SPARSE_EXT parameter to TRUE before allocating storage for it with TexStorage*. Insert Subsection 8.17sparse.1, "Allocation of and Access to Sparse Textures" Sparse textures are allocated setting a texture's TEXTURE_SPARSE_EXT parameter to TRUE and then issuing one of the TexStorage* commands. The dimensions of a sparse texture must be compatible with the internal format chosen for the texture. Each internal format has zero or more sparse page sizes that may be selected. The number of available page sizes for an internal format and the dimensions of the pages may be determined by calling GetInternalFormat* with the NUM_VIRTUAL_PAGE_SIZES_EXT (for the number of available page sizes), VIRTUAL_PAGE_SIZE_X_EXT, VIRTUAL_PAGE_SIZE_Y_EXT or VIRTUAL_PAGE_SIZE_Z_EXT (for the virtual page widths, heights and depths, respectively). Not all internal formats support sparse allocation. For those formats, the value of NUM_VIRTUAL_PAGE_SIZES_EXT will be zero. The internal formats which are guaranteed to support sparse allocation is listed in Table 8.13. Formats not listed as supported in Table 8.13 may still be supported by some implementations. The VIRTUAL_PAGE_SIZE_INDEX_EXT may be used to select the page layout for a sparse texture. The value of the texture's VIRTUAL_PAGE_SIZE_INDEX_EXT parameter is treated as an index into the array of possible page sizes for the type and requested internal format of the texture, and matches index of the array of values returned for the VIRTUAL_PAGE_SIZE_{XYZ}_EXT internal format query. When a sparsely committed texture is accessed by the GL, accesses that require only samples contained in committed regions complete as normal. For operations that access samples from uncommitted regions produce the following behavior: * Reads from such regions produce undefined data, but otherwise have no adverse effect. This includes samples required for the implementation of texture filtering, mipmap generation and so on. * Writes to such regions are ignored. The GL may attempt to write to uncommitted regions but the effect of doing so will be benign. * Atomic operations with return values on uncommitted regions will complete normally, but the returned value will be undefined and the result of the atomic operation will be discarded. * Reads and writes through framebuffers shall have no adverse effect, but fragment shaders corresponding to uncommitted regions of the framebuffer still execute to completion. Visible side effects of these shaders such as operations on atomic counters, storage blocks or committed regions of images are still seen, as are the results of operations such as occlusion queries. * Access to uncommitted regions by the client (for example through ReadPixels) shall have similar effect as through any other part of the GL --- reads return undefined data and writes are discarded, with no other ill effect. Insert Subsection 8.17sparse.2. "Controlling Sparse Texture Commitment" If a texture is allocated using sparse storage (that is, its TEXTURE_SPARSE_EXT parameter is TRUE at the time that its storage is allocated), it is initially created with only a virtual data store, and no physical data store. Individual pages of a sparse texture may be made resident or non-resident by calling void TexPageCommitmentEXT(enum target, int level, int xoffset, int yoffset, int zoffset, sizei width, sizei height, sizei depth, boolean commit); with and indicating the level of the texture object whose residency is to be modified. , , , , and are interpreted as they are in TexSubImage3D. An error will be generated unless , , , and specify a region of the texture level that is aligned to multiples of the page size or to the edges of the texture. If the value of is TRUE, then the texture pages contained in the region defined by the values of , , , , and are committed. If they were not committed before the call, then new physical backing store is allocated and associated with the sparse pages and their initial content is undefined. If the pages were already committed, then they remain committed, no error is generated, and the content of those pages remains unmodified. If the value of is FALSE, then the texture pages contained in the region are made de-committed. Their physical store is de-allocated, and their contents again become undefined. For the purposes of commitment, a cube map texture is treated as a 2D array texture with a depth of six and cube map array textures are treated as 2D array textures with a depth equal to six times the number of layers in the cube map array. For levels of a sparse texture where each dimension is a multiple of the virtual page size, the residency of individual page-size regions is controlled by TexPageCommitmentEXT and such levels may be partially populated. When the mipmap chain reaches a level that is not an integer multiple of the virtual page size in any dimension, padding and memory layout considerations may make it impossible to treat that level and subsequent smaller ones as partially populated. The set of levels that can be partially populated is implementation-dependent. The total number of levels that may be partially populated may be queried by calling GetTexParameter* with the NUM_SPARSE_LEVELS_EXT. The collection of texture levels that may not be partially populated, if any, consists of levels NUM_SPARSE_LEVELS_EXT and higher, and is referred to as the mipmap 'tail'. The levels comprising the tail are made resident or non-resident as a unit. The tail is resident if and only if TexPageCommitmentEXT has been called successfully with greater than or equal to NUM_SPARSE_LEVELS_EXT and the value of was TRUE for the last such call. Views of sparse textures are also considered sparse. Modifications to commitment of a texture via a view of it affect the parent texture and any other views containing the modified pages. If a view of a sparse texture references its tail (or is entirely contained within it), modifications to commitment of the tail via the view will affect the entire tail of the parent, even for parts of the tail that are not referenced by the view. Furthermore, modifications to tail commitment may affect views referencing other parts of the tail. Errors An INVALID_OPERATION error is generated if + or + is greater than the width or height, respectively, of level of the texture bound to . An INVALID_OPERATION error is generated if + is greater than * the depth of level of the texture bound to , if is TEXTURE_3D; * the number of layers of level of the texture bound to , if is TEXTURE_2D_ARRAY; * six times the number of layers of level of the texture bound to , if is TEXTURE_CUBE_MAP_ARRAY_OES; or * one, for all other targets. An INVALID_VALUE error is generated if , , or is not a multiple of VIRTUAL_PAGE_SIZE_X_EXT, VIRTUAL_PAGE_SIZE_Y_EXT, or VIRTUAL_PAGE_SIZE_Z_EXT, respectively, of the texture bound to . An INVALID_OPERATION error is generated if is not an integer multiple of VIRTUAL_PAGE_SIZE_X_EXT and plus is not equal to the width of level of the texture bound to . An INVALID_OPERATION error is generated if is not an integer multiple of VIRTUAL_PAGE_SIZE_Y_EXT and plus is not equal to the height of level of the texture bound to . An INVALID_OPERATION error is generated if is not an integer multiple of VIRTUAL_PAGE_SIZE_Z_EXT and plus is not equal to * the depth of level of the texture bound to , if is TEXTURE_3D; * the number of layers of level of the texture bound to , if is TEXTURE_2D_ARRAY; * six times the number of layers of level of the texture bound to , if is TEXTURE_CUBE_MAP_ARRAY; or * one, for all other targets. An INVALID_OPERATION error is generated if the value of TEXTURE_IMMUTABLE_FORMAT or TEXTURE_SPARSE_EXT for the texture bound to is FALSE. [[ The following is only added if EXT_direct_state_access is supported. ]] The command void TexturePageCommitmentEXT(uint texture, int level, int xoffset, int yoffset, int zoffset, sizei width, sizei height, sizei depth, boolean commit); may also be used to control the residency of sparse textures. This command behaves identically to TexPageCommitmentEXT, except that the texture is identified by the name instead of via . Errors An INVALID_OPERATION error is generated if is not the name of an existing texture. All other errors listed for TexPageCommitmentEXT also apply to TexturePageCommitmentEXT, except that references to "the texture bound to " should be replaced with "the texture ", and all other references to "" should be replaced with "the target of texture ". Additions to Chapter 19 of the OpenGL ES 3.1 Specification (Context State Queries) Append to Table 19.1, "Possible targets that internalformat can be used with and the corresponding usage meaning" +-------------------------------+-------------------------+ | Target | Usage | +-------------------------------+-------------------------+ | TEXTURE_2D | 2D texture | | TEXTURE_2D_ARRAY | 2D texture array | | TEXTURE_CUBE_MAP | Cube map texture | | TEXTURE_CUBE_MAP_ARRAY_OES | Cube map texture array | | TEXTURE_3D | 3D texture | +-------------------------------+-------------------------+ Modify Section 19.3.1, "Internal Format Query Parameters" (In the first item on the supported pnames list for NUM_SAMPLE_COUNTS, modify the first sub-list item "If does not support multiple samples..") - If is not color-renderable, depth-renderable, or stencil-renderable (as defined in section 9.4), or if does not support multiple samples (is not TEXTURE_2D_MULTISAMPLE. or RENDERBUFFER), zero is returned. (In the second item on the supported pnames list for SAMPLES, append to the sub-list) - If is not color-renderable, depth-renderable, or stencil-renderable (as defined in section 9.4), or if does not support multiple samples (is not TEXTURE_2D_MULTISAMPLE. or RENDERBUFFER), is not modified. (Add to supported pnames list) * NUM_VIRTUAL_PAGE_SIZES_EXT: The number of virtual page sizes supported by internalformat and target is written into params. Unsupported internal formats and targets report 0. * VIRTUAL_PAGE_SIZE_X_EXT: The virtual page widths supported for internalformat and target are written into params. * VIRTUAL_PAGE_SIZE_Y_EXT: The virtual page heights supported for internalformat and target are written into params. * VIRTUAL_PAGE_SIZE_Z_EXT: The virtual page depths supported for internalformat and target are written into params. In the error list on p.353, modify the first item: * An INVALID_ENUM error is generated if is not one of the targets in table 19.1, or if is not SAMPLES, NUM_SAMPLES_COUNTS, NUM_VIRTUAL_PAGE_SIZES_EXT, VIRTUAL_PAGE_SIZE_X_EXT, VIRTUAL_PAGE_SIZE_Y_EXT or VIRTUAL_PAGE_SIZE_Z_EXT. Remove the second item "An INVALID_ENUM error is generated if internalformat is not color-, depth- or stencil-renderable." Additions to the AGL/GLX/WGL/EGL Specifications None. GLX Protocol None. New State Append to Table 20.9, "Textures (state per texture object) (cont.)" +-----------------------------------+-------+---------------------+-----------------+---------------------------------------+-------------+ | Get Value | Type | Get Command | Initial Value | Description | Sec. | +-----------------------------------+-------+---------------------+-----------------+---------------------------------------+-------------+ | VIRTUAL_PAGE_SIZE_INDEX_EXT | Z+ | GetTexParameteriv | 0 | Virtual page size index | 8.17sparse | | TEXTURE_SPARSE_EXT | B | GetTexParameteriv | FALSE | Texture sparseness | 8.17sparse | | NUM_SPARSE_LEVELS_EXT | Z+ | GetTexParameteriv | 0 | Number of potentially sparse levels | 8.17sparse | +-----------------------------------+-------+---------------------+-----------------+---------------------------------------+-------------+ New Implementation Dependent State Append to Table 20.41, "Implementation Dependent Values" +--------------------------------------------+-------+-------------+-----------------+---------------------------------------+-------+ | Get Value | Type | Get Command | Minimum Value | Description | Sec. | +--------------------------------------------+-------+-------------+-----------------+---------------------------------------+-------+ | MAX_SPARSE_TEXTURE_SIZE_EXT | Z+ | GetIntegerv | 2048 | Maximum 1D/2D/rectangle texture image | 8.19 | | | | | | dimension for a sparse texture. | | | MAX_SPARSE_3D_TEXTURE_SIZE_EXT | Z+ | GetIntegerv | 256 | Maximum 3D texture image dimension | 8.19 | | | | | | for a sparse texture. | | | MAX_SPARSE_ARRAY_TEXTURE_LAYERS_EXT | Z+ | GetIntegerv | 256 | Maximum number of layers in a sparse | 8.19 | | | | | | array texture. | | | SPARSE_TEXTURE_FULL_ARRAY_CUBE_MIPMAPS_EXT | B | GetBooleanv | - | TRUE if there are no restrictions on | 8.19 | | | | | | the allocation of mipmaps in sparse | | | | | | | textures and FALSE otherwise. | | +--------------------------------------------+-------+-------------+-----------------+---------------------------------------+-------+ (Note the values of MAX_SPARSE_TEXTURE_SIZE_EXT, MAX_SPARSE_3D_TEXTURE_SIZE_EXT, MAX_SPARSE_ARRAY_TEXTURE_LAYERS_EXT must be at least as high as the corresponding non-sparse maximums. These values were 16384, 2048, and 2048 respectively in ARB_sparse_texture, reflecting the desktop texture size limits. They were reduced in this extension to reflect the ES 3.1 limits of 2048, 256, and 256.) Dependencies on OES_texture_view and EXT_texture_view If neither OES_texture_view nor EXT_texture_view is supported, then remove all references to texture views. Dependencies on OES_texture_border_clamp If OES_texture_border_clamp is not supported, ignore all references to TexParameterI{u}ivOES and GetTexParameterI{u}ivOES. Dependencies on EXT_texture_border_clamp If EXT_texture_border_clamp is not supported, ignore all references to TexParameterI{u}ivEXT and GetTexParameterI{u}ivEXT. Dependencies on OES_texture_cube_map_array and EXT_texture_cube_map_array If neither OES_texture_cube_map_array nor EXT_texture_cube_map_array is supported, ignore all references to cube map array textures and TEXTURE_CUBE_MAP_ARRAY_OES. If OES_texture_cube_map_array is not supported, but EXT_texture_cube_map_array is, replace all occurrences of TEXTURE_CUBE_MAP_ARRAY_OES with TEXTURE_CUBE_MAP_ARRAY_EXT. Dependencies on EXT_texture_norm16 If EXT_texture_norm16 is not supported, remove references to all texture formats added by that extension. These are: R16_EXT, R16_SNORM_EXT, RG16_EXT, RG16_SNORM_EXT, RGB16_EXT, RGB16_SNORM_EXT, RGBA16_EXT, and RGBA16_SNORM_EXT. Dependencies on GL_EXT_direct_state_access If the GL_EXT_direct_state_access extension is not supported, remove all references to TexturePageCommitmentEXT. Issues Note: Issues 1-9 are the same as those in the OpenGL extension ARB_sparse_texture, which can be found in the OpenGL Registry. They were retained here to aid in understanding the functionality. 0) How does this extension differ from ARB_sparse_texture? * It was rebased against OpenGL ES 3.1 and suffices converted from ARB to EXT. Interactions with ES extensions were added. * References to functions and texture formats not present in OpenGL ES were removed (GetDoublev, GetTexImage). 1) Do we want to mandate specific page sizes for specific formats? RESOLVED. No, this functionality is available in EXT_sparse_texture2. 2) What happened to MIN_SPARSE_LEVEL_AMD from the AMD spec? Do we need it here? RESOLVED. We changed it to NUM_SPARSE_LEVELS_EXT. MIN_SPARSE_LEVEL_AMD could not acceptably describe the case where a texture is technically sparse, but no level of the texture may be sparsely populated. The AMD specification disallowed creation of such a texture. However, this extension does allow creation of a texture that is either wholly resident or non-resident. Furthermore, if a view of a sparse texture is created starting somewhere in the tail, then that whole view is essentially sparse. 3) Should it be mandatory to support sparse allocation for compressed textures? RESOLVED: No, but in all likelihood, implementations will support some or all compressed texture formats. 4) Are multisample textures supported? What about depth and stencil format textures? RESOLVED: No. Depth and stencil format textures are optional to support. Providing support would be a case of reporting non-zero for NUM_VIRTUAL_PAGE_SIZES_EXT for those formats. Multi-sample textures are explicitly not supported by this extension as their targets are excluded from TexStorage* support. Allowing support for these would require a new extension, if only to remove the error generated if one of the multi-sample targets is used with TexStorage* when the sparse flag is set. 5) Do we need language clarifying completeness and the effects of residency on completeness? RESOLVED: Currently, there is no language. Textures allocated by TexStorage* (which include all sparse textures) are always complete. Residency doesn't effect that and sampling from them is well defined (or explicitly undefined). 6) Can commitment fail? What happens if it does? RESOLVED: An OUT_OF_MEMORY error is generated if physical backing cannot be allocated for the previously allocated virtual space. No language is added here as it is implicit that any command can generate OUT_OF_MEMORY at any time for any reason... which includes new commands introduced here. 7) Please explain, in plain English, what the rules are governing the size of a texture's base level, mipmap levels, and the 'tail'. The base level of the texture must be an integer multiple of the page size in each dimension. This need not be a power of two or square or anything of that nature. As we proceed along the mipmap chain, the current level will become smaller and smaller, at each step halving in size. At some point, the level dimensions will no longer be an integer multiple of the page size, where the memory corresponding to that level and smaller sized levels may not be evenly divided into pages. The memory allocated to such levels may not be naturally aligned on memory page boundaries or may be too small to bother with partial residency. Implementations are permitted to treat such a level and all subsequent levels as either fully resident or fully non-resident. We refer to this set of levels as the mipmap "tail". The set of levels belonging to the tail is implementation-dependent. Some implementations may start the tail at the first level where any dimension is not the multiple of a page size; others might pad out such allocations to page boundaries and start the tail at a much smaller mipmap level. The tail is made resident or non-resident as a unit; the tail is resident if and only if was TRUE for the last call to TexPageCommitmentEXT when was any value in the tail. Clearly, making the base level a square power of two multiple of the page size will mean that the greatest part of the texture can be sparse and will minimize the size of the tail. However, it's perfectly legal, with a hypothetical 256 x 256 texel page size to create a texture with a base level of 4096 x 256. Such a texture can be sparse in the base level, but level 1 would be 2048 x 128, which is no longer a multiple of the page size, and therefore might be considered as the start of the tail. 8) What's SPARSE_TEXTURE_FULL_ARRAY_CUBE_MIPMAPS_EXT for? Some implementations may store the mipmap chain for array textures and cubemaps such that the presence and size of mipmaps affects the alignment of the start of each layer, even in the base level. Consider an implementation that stores all layers of level 0, then all of level 1, then all of level 2 and so on. The presence of a mipmap chain (or lack thereof) would have no effect on the alignment of layers 1 through N of the array (or cubemap faces). Now, consider an implementation that stores all of the levels for layer 0, then all levels of layer 1 and so on. The number and size of the levels of the texture _would_ have an effect on the alignment of layers 1 through N of the texture. If the size of the mipmap chain for a single layer causes the next layer to become misaligned to the page size in linear address space, then the texture cannot be sparsely populated. This flag indicates whether the implementation has any restrictions on the size of the mipmap chain. In particular, these restrictions ensure that, while the texture may have mipmaps, the total size of the mipmap chain for each level still satisfies the alignment restrictions required by that implementation's virtual memory subsystem. 9) What happens when you create a view of a sparse texture? RESOLVED: That view is sparse, as are views of that view and so on. Also, if the view hits the tail, then modifications of tail residency via the view affect the whole tail of the parent texture. Revision History Rev. Date Author Changes ---- ---------- -------- ----------------------------------------- 3 03/27/2015 dkoch update status and contributors 2 02/25/2015 xiche Additional interaction with GetInternalformativ 1 11/13/2014 dkoch Initial version based on ARB_sparse_texture v11