| Name |
| |
| OES_shader_image_atomic |
| |
| Name Strings |
| |
| GL_OES_shader_image_atomic |
| |
| Contact |
| |
| Bill Licea-Kane, Qualcomm Technologies, Inc. ( billl 'at' qti.qualcomm.com ) |
| |
| Contributors |
| |
| Jeff Bolz, NVIDIA |
| Pat Brown, NVIDIA |
| Daniel Koch, NVIDIA |
| Jon Leech |
| Barthold Lichtenbelt, NVIDIA |
| Bill Licea-Kane, AMD |
| Eric Werness, NVIDIA |
| Graham Sellers, AMD |
| Greg Roth, NVIDIA |
| Nick Haemel, AMD |
| Pierre Boudier, AMD |
| Piers Daniell, NVIDIA |
| |
| Notice |
| |
| Copyright (c) 2011-2015 The Khronos Group Inc. Copyright termsat |
| 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 ES 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. |
| Ratified by the Khronos Board of Promoters on 2014/03/14. |
| |
| Version |
| |
| Last Modified Date: April 30, 2015 |
| Revision: 5 |
| |
| Number |
| |
| OpenGL ES Extension #171 |
| |
| Dependencies |
| |
| This extension is written against the OpenGL ES Version 3.1 (April 29, |
| 2015) Specification. |
| |
| This extension is written against the OpenGL ES Shading Language 3.10, |
| Revision 3, 6 June 2014 Specification. |
| |
| OpenGL ES 3.1 and GLSL ES 3.10 are required. |
| |
| Overview |
| |
| This extension provides built-in functions allowing shaders to perform |
| atomic read-modify-write operations to a single level of a texture |
| object from any shader stage. These built-in functions are named |
| imageAtomic*(), and accept integer texel coordinates to identify the |
| texel accessed. These built-in functions extend the Images in ESSL 3.10. |
| |
| Additions to Chapter 7 of the OpenGL ES 3.1 specification (Programs and Shaders) |
| |
| Change the first paragraph of section 7.10 "Images" on p. 113: |
| |
| "Images are special uniforms used in the OpenGL ES Shading Language to |
| identify a level of a texture to be read or written using image load, |
| store, and atomic built-in functions in the manner ..." |
| |
| |
| Change the third paragraph of section 7.10: |
| |
| "The type of an image variable must match the texture target of the image |
| currently bound to the image unit, otherwise the result of a load, |
| store, or atomic operation..." |
| |
| |
| Change the first sentence of section 7.11 "Shader Memory Access" on p. |
| 113: |
| |
| "... shader buffer variables, or to texture or buffer object memory using |
| built-in image load, store, and atomic functions operating on shader |
| image variables..." |
| |
| Additions to Chapter 8 of the OpenGL ES 3.1 specification (Textures and Samplers) |
| |
| Change the caption to table 8.26, p. 199 |
| |
| "Table 8.26: Mapping of image load, store, and atomic texel..." |
| |
| |
| Change the first sentence of the second paragraph on p. 199: |
| |
| "When a shader accesses the texture bound to an image unit using a |
| built-in image load, store or atomic function..." |
| |
| |
| Change the fourth paragraph: |
| |
| "If the individual texel identified for an image load, store, or atomic |
| operation ... Invalid image stores will have no effect. Invalid image |
| atomics will not update any texture bound to the image unit and will |
| return zero. An access is considered invalid if..." |
| |
| |
| Change the first complete paragraph on p. 200: |
| |
| "Additionally, there are a number of cases where image load, store, or |
| atomic operations are considered to involve a format mismatch. In such |
| cases, undefined values will be returned by image loads and atomic |
| operations, and undefined values will be written by stores and atomic |
| operations. A format mismatch will occur if:" |
| |
| |
| Change the last paragraph on p. 200: |
| |
| "Any image variable used for shader loads or atomic memory operations |
| must be declared with a format <layout> qualifier matching ..." |
| |
| |
| Change the last paragraph on p. 200: |
| |
| "When the format associated with an image unit does not exactly match the |
| internal format of the texture bound to the image unit, image loads, |
| stores and atomic operations re-interpret the memory holding the |
| components of an accessed texel according to the format of the image |
| unit. The re-interpretation for image loads and the read portion of |
| image atomics is performed as though data were copied from the texel of |
| the bound texture to a similar texel represented in the format of the |
| image unit. Similarly, the re-interpretation for image stores and the |
| write portion of image atomics is performed as though ..." |
| |
| Changes to Chapter 20 (State Tables) |
| |
| Modify the description of MAX_IMAGE_UNITS in table 20.47 on p. 404: |
| |
| "MAX_IMAGE_UNITS ... No. of units for image load/store/atomics" |
| |
| Additions to Appendix A of the OpenGL ES 3.1 specification (Invariance) |
| |
| Change the third sentence of the first paragraph in section A.1, p. 408: |
| |
| "This repeatability requirement doesn't apply when using shaders |
| containing side effects (image stores, image atomic operations, atomic |
| counter operations ..." |
| |
| |
| Change the last sentence of Rule 4 in section A.3, p. 310: |
| |
| "Invariance is relaxed for shaders with side effects, such as image |
| stores, image atomic operations, or accessing atomic counters (see |
| section A.4)." |
| |
| |
| Change the first sentence of the second paragraph of Rule 5, p. 310: |
| |
| "If a sequence of GL commands specifies primitives to be rendered with |
| shaders containing side effects (image stores, image atomic operations, |
| atomic counter operations ..." |
| |
| |
| Change the first sentence of Rule 6, p. 411: |
| |
| "For any given GL and framebuffer state vector, and for any given GL |
| command, the contents of any framebuffer state not directly or |
| indirectly affected by results of shader image stores, image atomic |
| operations, or atomic counter operations ..." |
| |
| |
| Change the first bullet of Rule 7, p. 411: |
| |
| "* shader invocations do not use image atomic operations or atomic |
| counters;" |
| |
| |
| Change the first sentence of the second paragraph of Rule 7: |
| |
| "When any sequence of GL commands triggers shader invocations that |
| perform image stores, image atomic operations, atomic counter |
| operations ..." |
| |
| |
| Modifications to the OpenGL ES 3.10 Shading Language Specification |
| |
| Including the following line in a shader can be used to control the |
| language features described in this extension: |
| |
| #extension GL_OES_shader_image_atomic : <behavior> |
| |
| where <behavior> is as specified in section 3.3. |
| |
| New preprocessor #defines are added to the OpenGL Shading Language: |
| |
| #define GL_OES_shader_image_atomic |
| |
| |
| Modifications to Chapter 4 (Variables and Types) of the OpenGL ES 3.10 |
| Shading Language Specification |
| |
| Change the first sentence of the third paragraph of section 4.1.7.2 |
| (Images), p. 28: |
| |
| "Image variables are used in the image load, store, and |
| atomic functions described in section 8.12 ..." |
| |
| |
| Add to section 8.12 (Image Functions) |
| |
| Add new overview and syntax and description table following existing |
| Image Functions table, p. 129: |
| |
| "The atomic functions perform operations on individual texels or samples |
| of an image variable. Atomic memory operations read a value from the |
| selected texel, compute a new value using one of the operations |
| described below, write the new value to the selected texel, and return |
| the original value read. The contents of the texel being updated by the |
| atomic operation are guaranteed not to be updated by any other image |
| store or atomic function between the time the original value is read and |
| the time the new value is written. |
| |
| Atomic memory operations are supported on only a subset of all image |
| variable types; <image> must be either: |
| |
| * a signed integer image variable (type starts "iimage") and a format |
| qualifier of "r32i", used with a <data> argument of type "int", or |
| * an unsigned integer image variable (type starts "uimage") and a |
| format qualifier of "r32ui", used with a <data> argument of type |
| "uint", or |
| * a float image variable (type starts "image") and a format qualifier |
| of "r32f", used with a <data> argument of type "float" |
| (imageAtomicExchange only). |
| |
| Add to the table of image functions, p. 129: |
| |
| Syntax Description |
| ------------------------------- ------------------------------------- |
| highp uint imageAtomicAdd( Computes a new value by adding the |
| coherent IMAGE_PARAMS, value of <data> to the contents of |
| uint data); the selected texel. |
| highp int imageAtomicAdd( |
| coherent IMAGE_PARAMS, |
| int data); |
| ----------------------------------------------------------------------- |
| highp uint imageAtomicMin( Computes a new value by taking the |
| coherent IMAGE_PARAMS, minimum of the value of <data> and |
| uint data); the contents of the selected texel. |
| highp int imageAtomicMin( |
| coherent IMAGE_PARAMS, |
| int data); |
| ----------------------------------------------------------------------- |
| highp uint imageAtomicMax( Computes a new value by taking the |
| coherent IMAGE_PARAMS, maximum of the value of <data> and |
| uint data); the contents of the selected texel. |
| highp int imageAtomicMax( |
| coherent IMAGE_PARAMS, |
| int data); |
| ----------------------------------------------------------------------- |
| highp uint imageAtomicAnd( Computes a new value by performing a |
| coherent IMAGE_PARAMS, bitwise AND of the value of <data> |
| uint data); and the contents of the selected |
| highp int imageAtomicAnd( texel. |
| coherent IMAGE_PARAMS, |
| int data); |
| ----------------------------------------------------------------------- |
| highp uint imageAtomicOr( Computes a new value by performing a |
| coherent IMAGE_PARAMS, bitwise OR of the value of <data> |
| uint data); and the contents of the selected |
| highp int imageAtomicOr( texel. |
| coherent IMAGE_PARAMS, |
| int data); |
| ----------------------------------------------------------------------- |
| highp uint imageAtomicXor( Computes a new value by performing a |
| coherent IMAGE_PARAMS, bitwise EXCLUSIVE OR of the value of |
| uint data); <data> and the contents of the |
| highp int imageAtomicXor( selected texel. |
| coherent IMAGE_PARAMS, |
| int data); |
| ----------------------------------------------------------------------- |
| highp uint imageAtomicExchange( Computes a new value by simply |
| coherent IMAGE_PARAMS, copying the value of <data>. |
| uint data); |
| highp int imageAtomicExchange( |
| coherent IMAGE_PARAMS, |
| int data); |
| highp float imageAtomicExchange( |
| coherent IMAGE_PARAMS, |
| float data); |
| ----------------------------------------------------------------------- |
| highp uint imageAtomicCompSwap( Compares the value of <compare> and |
| coherent IMAGE_PARAMS, the contents of the selected texel. |
| uint compare, If the values are equal, the new |
| uint data); value is given by <data>; otherwise, |
| highp int imageAtomicCompSwap( it is taken from the original value |
| coherent IMAGE_PARAMS, loaded from the texel. |
| int compare, |
| int data); |
| ----------------------------------------------------------------------- |
| |
| Issues |
| |
| (0) This extension is based on ARB_shader_image_load_store. What |
| are the major differences? |
| |
| 1 - This extension splits out only the image atomic operations |
| from ARB_shader_image_load_store. |
| 2 - It depends on image load/store functionality that is part of |
| OpenGL ES 3.1, and inherits the list of differences from |
| desktop implementations in ES 3.1. Note that issue 0 of the |
| (unpublished) XXX_shader_image_load_store used for prototyping |
| ES 3.1 language contains the list explicitly; perhaps it should |
| should be reproduced here as well. |
| |
| (1) Should the shading language built-ins have OES suffixes? |
| |
| RESOLVED: No. Per Bug 11637, the WG made a policy decision |
| that GLSL ES identifiers imported without semantic change |
| or subsetting as OES extensions from core GLSL do not carry |
| suffixes. The #extension mechanism must still be used to |
| enable the appropriate extension before the functionality can |
| be used. |
| |
| Revision History |
| |
| Rev. Date Author Changes |
| 1 2014-01-30 wwlk Initial draft |
| 2 2014-01-31 wwlk Update to current draft base specs |
| (further updates coming as |
| additional draft specs done. |
| Otherwise, this spec is probably |
| ready to review.) |
| 3 2014-02-11 dkoch remove GLSL builtin suffixes per issue 1. |
| 4 2014-03-04 dkoch add coherent to image parameter (Bug 11595) |
| 5 2015-04-30 Jon Leech Require OpenGL ES 3.1 and remove dependency |
| on nonexistent shader_image_load_store |
| extension. Rewrite changes against the |
| published ES 3.1 / ESSL 3.10 specifications. |
| Remove references to multisampled image |
| atomic support, which does not exist in ES |
| 3.1. (Bugs 13879, 13887) |
