| Name |
| |
| ARB_shader_texture_image_samples |
| |
| Name Strings |
| |
| GL_ARB_shader_texture_image_samples |
| |
| Contact |
| |
| Piers Daniell, NVIDIA (pdaniell@nvidia.com) |
| Mathias Schott, NVIDIA (mschott@nvidia.com) |
| |
| Contributors |
| |
| Tristan Lorach, NVIDIA (tlorach@nvidia.com) |
| Christophe Riccio, Unity (christophe.riccio@unity3d.com) |
| Evan Hart, NVIDIA (ehart@nvidia.com) |
| Jeannot Breton, NVIDIA (jbreton@nvidia.com) |
| |
| Notice |
| |
| Copyright (c) 2014 The Khronos Group Inc. Copyright terms at |
| http://www.khronos.org/registry/speccopyright.html |
| |
| Specification Update Policy |
| |
| Khronos-approved extension specifications are updated in response to |
| issues and bugs prioritized by the Khronos OpenGL Working Group. For |
| extensions which have been promoted to a core Specification, fixes will |
| first appear in the latest version of that core Specification, and will |
| eventually be backported to the extension document. This policy is |
| described in more detail at |
| https://www.khronos.org/registry/OpenGL/docs/update_policy.php |
| |
| Status |
| |
| Complete. |
| Approved by the ARB on June 26, 2014. |
| Ratified by the Khronos Board of Promoters on August 7, 2014. |
| |
| Version |
| |
| Last Modified Date: May 28, 2014 |
| Revision: 7 |
| |
| Number |
| |
| ARB Extension #166 |
| |
| Dependencies |
| |
| Either GLSL 1.50 or ARB_texture_multisample is required. |
| |
| This extension is written against the OpenGL 4.4 specification and |
| version 4.40 of the OpenGL Shading Language Specification. |
| |
| This extension interacts with ARB_shader_image_load_store and GLSL 4.20. |
| |
| This extension interacts with NV_gpu_program5, EXT_shader_image_load_store |
| and NV_texture_multisample. |
| |
| Overview |
| |
| This extension provides GLSL built-in functions allowing shaders to query |
| the number of samples of a texture. |
| |
| New Procedures and Functions |
| |
| None. |
| |
| New Tokens |
| |
| None. |
| |
| Additions to the OpenGL 4.4 (Core Profile) Specification |
| |
| None. |
| |
| Errors |
| |
| None. |
| |
| New State |
| |
| None. |
| |
| New Implementation Dependent State |
| |
| None. |
| |
| Modifications to The OpenGL Shading Language Specification, Version 4.40.08 |
| |
| Including the following line in a shader can be used to control the |
| language features described in this extension: |
| |
| #extension GL_ARB_shader_texture_image_samples |
| |
| A new preprocessor #define is added to the OpenGL Shading Language: |
| |
| #define GL_ARB_shader_texture_image_samples 1 |
| |
| Add to table in section 8.9.1 "Texture Query Functions" |
| |
| Syntax: |
| |
| int textureSamples(gsampler2DMS sampler) |
| int textureSamples(gsampler2DMSArray sampler) |
| |
| Description: |
| |
| Returns the number of samples of the texture or textures bound to |
| <sampler>. |
| |
| Add to table in section 8.12 "Image Functions" |
| |
| Syntax: |
| |
| int imageSamples(gimage2DMS image) |
| int imageSamples(gimage2DMSArray image) |
| |
| Description: |
| |
| Returns the number of samples of the image or images bound to <image>. |
| |
| Dependencies on ARB_shader_image_load_store and GLSL 4.20. |
| |
| If neither ARB_shader_image_load_store nor GLSL 4.20 is enabled in the |
| shader, then all overloads of imageSamples are removed. |
| |
| Dependencies on NV_gpu_program5, EXT_shader_image_load_store and |
| NV_texture_multisample |
| |
| If NV_gpu_program5, EXT_shader_image_load_store and NV_texture_multisample |
| are supported, and "OPTION ARB_shader_texture_image_samples" is specified |
| in an assembly program, the following edits are made to extend the assembly |
| programming model documented in the NV_gpu_program4 extension and extended |
| by NV_gpu_program5, EXT_shader_image_load_store and NV_texture_multisample. |
| |
| If NV_gpu_program5, EXT_shader_image_load_store or NV_texture_multisample |
| are not supported, or if "OPTION ARB_shader_texture_image_samples" is not |
| specified in an assembly program, the contents of this dependencies section |
| should be ignored. |
| |
| Section 2.X.2, Program Grammar |
| |
| (add the following rules to the grammar) |
| |
| <ImageInstruction> ::= <IMQSop_instruction> |
| |
| <IMQSop_instruction> ::= <IMQSop> <opModifiers> <instResult> "," |
| <imageAccess> |
| |
| <IMQSop> ::= "IMQS" |
| |
| <TEXop_instruction> ::= <TXQSop> <opModifiers> <instResult> "," |
| <texAccess> |
| |
| <TXQSop> ::= "TXQS" |
| |
| |
| Modify Section 2.X.4, Program Execution Environment |
| |
| Instr- Modifiers |
| uction V F I C S H D Out Inputs Description |
| ------- -- - - - - - - --- -------- -------------------------------- |
| IMQS 50 - - - - - S s i image sample query |
| TXQS 50 - - - - - S s t texture sample query |
| |
| (Add to "Section 2.X.6, Program Options" of the NV_gpu_program4 extension, |
| as extended by NV_gpu_program5) |
| |
| + Texture and image sample query (ARB_shader_texture_image_samples) |
| |
| If a program specifies the "ARB_shader_texture_image_samples" option, it |
| may use the instructions TXQS and IMQS. If this option is not specified, |
| a program will fail to compile if it uses one of those two instructions. |
| |
| |
| Section 2.X.8.Z, IMQS: Image sample query |
| |
| The IMQS instruction returns the number of samples of the image unit |
| specified by <imageUnit>. Two image targets are supported: 2DMS and |
| ARRAY2DMS. If the texture bound to the image unit has a TEXTURE_SAMPLES |
| value of 0, the instruction will return 1. IMQS supports no data type |
| modifiers; the result scalar is interpreted as a signed integer. IMQS |
| supports no storage modifier, since the number of sample is independent of |
| the image unit format. |
| |
| |
| Section 2.X.8.Z, TXQS: Texture sample query |
| |
| The TXQS instruction returns the number of samples of the texture image |
| unit specified by <texImageUnit>. Two texture targets are supported: |
| 2DMS and ARRAY2DMS. If the texture has a TEXTURE_SAMPLES value of 0, the |
| instruction will return 1. TXQS supports no data type modifiers; the |
| result scalar is interpreted as a signed integer. |
| |
| |
| Conformance Tests |
| |
| <TBD> |
| |
| Issues |
| |
| (1) What should we call this extension? |
| |
| GL_ARB_shader_image_size added imageSize which apparently was missed |
| from GL_ARB_shader_image_load_store |
| GL_ARB_texture_multisample had textureSize built in, so no precedence |
| |
| Ideas: |
| * GL_ARB_shader_sample_count_query |
| * GL_ARB_shader_samples_query |
| * GL_ARB_shader_texture_image_sample_count_query |
| * GL_ARB_shader_texture_image_samples |
| * GL_ARB_shader_texture_image_size_multisample |
| * GL_ARB_shader_texture_image_samples |
| * GL_ARB_shader_texture_samples |
| |
| RESOLVED: ARB_shader_texture_image_samples for now to |
| follow the precedent set by GL_ARB_shader_image_size. |
| |
| Might change depending on what the final resolution is for Issue (2) |
| |
| (2) How should we expose this? |
| |
| (A) separate textureSamples/imageSamples functions to query |
| just the number of samples |
| |
| orthogonal to other functions, makes it also easy to add non-awkward |
| versions for non MS textures that return 1. |
| |
| (B) (like that other API): extend textureSize/imageSize to return another |
| component in the returned (vec) value |
| |
| impossible to overload functions based on return type |
| |
| (C) textureSizeMS/imageSizeMS functions that return the number |
| of samples in the last component of the returned (vec) value |
| |
| Closer to that other API, but ugly and awkward to have non-ms textures |
| as arguments for a *SizeMS function. |
| |
| GL_ARB_texture_multisample Issue (5) suggests A) or (C) as options |
| |
| RESOLVED: Option A |
| |
| (3) Do we need overloads for g*Shadow samplers |
| |
| For consistency with textureSize. |
| |
| RESOLVED: No, see issue (5). |
| |
| (4) What other extensions interact with this |
| |
| NV_gpu_program5, EXT_shader_image_load_store, and NV_texture_multisample. |
| |
| What's the minimal GL/GLSL version we need to depend on. |
| |
| RESOLVED: The functionality added by this extension is |
| perfectly well defined in any shading language version that |
| supports multisample textures. If the shading language, with |
| extensions, does not support images, then imageSamples is not |
| available. |
| |
| (5) Do we need overloads for non-MS textures and images |
| |
| RESOLVED: No, since the always would return 1. If required, users can create |
| their own overloads that return 1 for non-MS samplers. |
| |
| (6) Should we add functions to query the position of a sample |
| |
| RESOLVED: No because of the complexity and implementation burden |
| of supporting queries of multisample texture created with |
| fixedsamplelocation as false. In that case each pixel might have |
| different sample locations. If the app really needs to know the |
| sample location inside the shader it can pass in this data as |
| a uniforms initialized from GetMultisamplefv(SAMPLE_POSITION) |
| queries. |
| |
| Revision History |
| Revision 8, 2015/09/08 (idr) |
| - Add interactions with various GLSL versions and extensions so |
| that this extension can be used with any GLSL version. |
| |
| Revision 7, 2014/05/28 (mschott) |
| - Minor cleanups of NV_gpu_program5 dependencies in issue 5 and the introduction |
| |
| Revision 6, 2014/05/27 (jbreton) |
| - Add NV_gpu_program5 dependencies |
| |
| Revision 5, 2014/04/16 (pdaniell) |
| - Removed textureSamplePosition and imageSamplePosition |
| - Resolved issue 6 |
| |
| Revision 4, 2014/04/09 (mschott) |
| - added textureSamplePosition and imageSamplePosition |
| - added issue 6 |
| |
| Revision 3, 2014/03/31 (mschott) |
| - removed non-MS overloads |
| - added issue 5 |
| |
| Revision 2, 2013/12/13 (mschott) |
| - Renamed to GL_ARB_texture_image_samples |
| - added shadow sampler overloads |
| |
| Revision 1, 2013/12/13 (mschott) |
| - First draft |
