Merge pull request #207 from jackohound/add_QCOM_shader_framebuffer_fetch_rate_2
Add QCOM_shader_framebuffer_fetch_rate
diff --git a/extensions/QCOM/QCOM_shader_framebuffer_fetch_rate.txt b/extensions/QCOM/QCOM_shader_framebuffer_fetch_rate.txt
new file mode 100644
index 0000000..99f6b45
--- /dev/null
+++ b/extensions/QCOM/QCOM_shader_framebuffer_fetch_rate.txt
@@ -0,0 +1,264 @@
+Name
+ QCOM_shader_framebuffer_fetch_rate
+
+Name Strings
+
+ GL_QCOM_shader_framebuffer_fetch_rate
+
+Contact
+
+ Jeff Leger ( jleger 'at' qti.qualcomm.com)
+
+Contributors
+
+ Jeff Leger, Qualcomm
+ Jonathan Wicks, Qualcomm
+
+Status
+
+ DRAFT
+
+Version
+
+ Last Modified Date: August 20, 2018
+ Revision: 1
+
+Number
+
+ OpenGL ES Extension #304
+
+
+Dependencies
+
+ OpenGL ES 2.0 and GLSL ES 1.00 are required.
+
+ This extension is written against the OpenGL ES 3.2 (May 14, 2018)
+ and the OpenGL ES Shading Language 3.20.4 Specification
+ (June 14, 2018) specifications.
+
+ This extension interacts with EXT_shader_framebuffer_fetch.
+ This extension interacts with ARM_shader_framebuffer_fetch_depth_stencil.
+
+Overview
+
+ When certain built-ins (e.g. gl_LastFragData, gl_LastFragStencilARM)
+ are referenced in the shader, the shader is required to execute at sample-rate
+ if the attachments are multisampled. In some use-cases executing such shaders
+ at fragment-rate is actually the preferred behavior. When this extension is
+ enabled, such GLSL shaders will execute at fragment-rate and the built-in
+ will return a per-fragment value. This avoids the significant performance
+ penalty that would otherwise be incurred with sample-rate shading.
+
+ The following built-ins are affected when the this extension is enabled:
+
+ gl_LastFragData (from EXT_shader_framebuffer_fetch)
+ gl_LastFragDepthARM (from ARM_shader_framebuffer_fetch_depth_stencil)
+
+ The following built-ins are disallowed when this extension is enabled:
+
+ gl_SampleID
+ gl_SamplePosition
+ interpolateAtSample()
+
+IP Status
+
+ No known IP claims.
+
+New Procedures and Functions
+
+ None
+
+New Tokens
+
+ None
+
+Additions to Chapter 13 of the OpenGL ES 3.2 Specification
+(Fixed-Function Primitive Assembly and Rasterization)
+
+ Modify Section 13.4.1, Sample Shading, p. 353
+
+ Modify the first paragraph:
+ "Sample shading can be used to specify a minimum number of unique samples
+ to process for each fragment. Sample shading is controlled by calling
+ Enable or Disable with target SAMPLE_SHADING."
+
+ by adding one sentence to the end:
+ "Sample shading can be used to specify a minimum number of unique samples
+ to process for each fragment. Sample shading is controlled by calling
+ Enable or Disable with target SAMPLE_SHADING. For any fragment shader
+ that has forced fragment-rate by enabling QCOM_shader_framebuffer_fetch_rate,
+ such shader will execute as if SAMPLE_SHADING is disabled."
+
+Additions to Chapter 14 (Programmable Fragment Processing) of the OpenGL ES 3.2 Specification
+
+
+ Modify Section 14.2.2 (Shader Inputs), p. 372
+
+ Modify the sentence:
+ "Using gl_SampleID in a fragment shader causes the entire shader to
+ be executed per-sample."
+
+ to:
+ "Using gl_SampleID in a fragment shader causes the entire shader to
+ be executed per-sample. If GL_QCOM_shader_framebuffer_fetch_rate is
+ enabled, any use of gl_SampleID will result in a compile or link error."
+
+ Modify the sentence:
+ "Using gl_SamplePosition in a fragment shader causes the entire shader to
+ be executed per-sample."
+
+ to:
+ "Using gl_SamplePosition in a fragment shader causes the entire shader to
+ be executed per-sample. If GL_QCOM_shader_framebuffer_fetch_rate is
+ enabled, any use of gl_SamplePosition will result in a compile or link
+ error."
+
+
+ Modify Section 14.2.3 (Shader Outputs), p. 372
+
+ [[ The following applies if EXT_shader_framebuffer_fetch is supported ]]
+
+ In the new paragraphs added by EXT_shader_framebuffer_fetch to the end
+ this section, change the following added sentence:
+
+ From:
+ "Reading from a user-defined fragment output declared inout
+ causes the shader to be evaluated per-sample, since the
+ framebuffer potentially contains different color values for
+ each sample."
+
+ To:
+ "If QCOM_shader_framebuffer_fetch_rate is not enabled, reading from
+ a user-defined fragment output declared inout causes the shader
+ to be evaluated per-sample, since the framebuffer potentially
+ contains different color values for each sample."
+
+ Add the following paragraph to the end of "Shader Outputs" section:
+
+ "If the current rendertarget is multisampled and if
+ QCOM_shader_framebuffer_fetch_rate is enabled, then reading from
+ a user-defined fragment output declared inout will return an
+ implementation-dependent weighted average of the samples within
+ the destination pixel covered by the current fragment. The value
+ will be between the minium and maximum value of the covered samples.
+ If the destination colors must be linearized from sRGB as
+ described in the preceding paragraphs, the conversion from sRGB
+ to linear happens before computing the weighted average.
+
+Additions to the EGL Specifications
+
+ None.
+
+Modifications to The OpenGL ES Shading Language Specification, Version 3.20.4
+
+ Changes to section 7.1.5. (Fragment Shader Special Variables), p 120.
+
+ Add the following at the start of this section:
+
+ "Static use of certain built-in variables described in this section
+ will cause the shader to be evaluated per-sample. This language feature
+ can be optionally disabled, forcing such shaders to evaluate per-
+ fragment. The optional behavior can be enabled using:
+
+ #extension GL_QCOM_shader_framebuffer_fetch_rate : <behavior>
+
+ where <behavior> is as specified in section 3.4 (Preprocessor).
+
+ If GL_QCOM_shader_framebuffer_fetch_rate is enabled, it is a compile-time
+ or link-time error if any variable is declared with the "sample"
+ qualifier or if the built-in function interpolateAtSample() is statically
+ referenced."
+
+ Add the New preprocessor #defines are added to the OpenGL ES Shading Language:
+
+ "#define GL_QCOM_shader_framebuffer_fetch_rate 1"
+
+ Modify the last sentence of the paragraph starting with "The input variable
+ gl_SampleID is filled with the sample number of the sample currently being
+ processed"
+
+ from:
+ "Any static use of this variable in a fragment shader causes the entire
+ shader to be evaluated per-sample."
+ to
+ "If GL_QCOM_shader_framebuffer_fetch_rate is not enabled, any static use
+ of this variable in a fragment shader causes the entire shader to be evaluated
+ per-sample. If GL_QCOM_shader_framebuffer_fetch_rate is enabled, an static
+ reference to gl_SampleID will cause a compile or link error."
+
+ Modify the last sentence of the paragraph starting with "The input variable
+ gl_SamplePosition contains the position of the current sample within the
+ multisample draw buffer."
+
+ from:
+ "Any static use of this variable in a fragment shader causes the entire
+ shader to be evaluated per-sample."
+ to
+ "If GL_QCOM_shader_framebuffer_fetch_rate is not enabled, any static use of
+ this variable in a fragment shader causes the entire shader to be evaluated
+ per-sample. If GL_QCOM_shader_framebuffer_fetch_rate is enabled, an static
+ reference to gl_SamplePosition will cause a compile or link error."
+
+Interactions with EXT_shader_framebuffer_fetch.
+
+ Extension EXT_shader_framebuffer_fetch adds built-ins (gl_LastFragData[] for
+ version 1.0 shaders and inout variables version 3.0 shaders) that cause fragment
+ shaders to run at sample-rate. This extension relaxes that requirement to
+ allow fragment-rate and specifies that the value returned from gl_LastFragData
+ will be an implementation-dependent weighted average of the covered pixels.
+
+Interactions with ARM_shader_framebuffer_fetch_depth_stencil.
+
+ Extension ARM_shader_framebuffer_fetch adds built-in "gl_LastFragDepthARM",
+ and specifies the value returned -- for both sample-rate and fragment-rate
+ execution. This extension can be used to control whether sample-rate or
+ fragment-rate execution is used.
+
+Errors
+
+ None.
+
+New State
+
+ None.
+
+New Implementation Dependent State
+
+ None
+
+Issues
+
+ (1) Does it make sense to enable this extension for a shader that references
+ per-sample built-ins like gl_SampleID and gl_SamplePosition?
+
+ RESOLVED: No. It doesn't make sense to force fragment-rate
+ execution using this extension, while also referencing per-sample
+ built-ins. Since there is no known use-case, this will be a compile
+ or link error.
+
+ For the same reason, using the "sample" qualifier or using
+ interpolateAtSample() will cause a compile or link error.
+
+ (2) How does this extension interact with API-controlled sample-rate shading?
+
+ RESOLVED: For shaders that enable this this extension, those the shaders
+ will always execute at fragment-rate, regardless of other API states.
+ In particular, the enable/disable of SAMPLE_SHADING and the value of
+ MIN_SAMPLE_SHADING_VALUE will have no effect on such shaders.
+
+ (3) How does this extension differ from ARM_shader_framebuffer_fetch?
+
+ ARM_shader_framebuffer_fetch provides a means for controlling whether
+ shaders fetching color from the framebuffer should execute at sample-rate or
+ fragement rate. The API state "FETCH_PER_SAMPLE_ARM" controls
+ this behavior.
+
+ This extension also provides control over sample-rate vs fragment-rate
+ for framebuffer fetch shaders, but does so in the GLSL shader. Some
+ implementations require this information at shader compile time.
+
+Revision History
+
+ Rev. Date Author Changes
+ ---- ---------- -------- -----------------------------------------
+ 1 2018-08-20 jleger initial version
diff --git a/extensions/esext.php b/extensions/esext.php
index a209ec6..8deb772 100644
--- a/extensions/esext.php
+++ b/extensions/esext.php
@@ -631,4 +631,6 @@
</li>
<li value=303><a href="extensions/AMD/AMD_framebuffer_multisample_advanced.txt">GL_AMD_framebuffer_multisample_advanced</a>
</li>
+<li value=304><a href="extensions/QCOM/QCOM_shader_framebuffer_fetch_rate.txt">GL_QCOM_shader_framebuffer_fetch_rate</a>
+</li>
</ol>
diff --git a/extensions/registry.py b/extensions/registry.py
index 2b0bec5..0f36d45 100644
--- a/extensions/registry.py
+++ b/extensions/registry.py
@@ -4324,11 +4324,31 @@
'flags' : { 'public' },
'url' : 'extensions/QCOM/QCOM_extended_get2.txt',
},
+ 'GL_QCOM_framebuffer_foveated' : {
+ 'esnumber' : 273,
+ 'flags' : { 'public' },
+ 'url' : 'extensions/QCOM/QCOM_framebuffer_foveated.txt',
+ },
'GL_QCOM_performance_monitor_global_mode' : {
'esnumber' : 56,
'flags' : { 'public' },
'url' : 'extensions/QCOM/QCOM_performance_monitor_global_mode.txt',
},
+ 'GL_QCOM_shader_framebuffer_fetch_noncoherent' : {
+ 'esnumber' : 277,
+ 'flags' : { 'public' },
+ 'url' : 'extensions/QCOM/QCOM_shader_framebuffer_fetch_noncoherent.txt',
+ },
+ 'GL_QCOM_shader_framebuffer_fetch_rate' : {
+ 'esnumber' : 304,
+ 'flags' : { 'public' },
+ 'url' : 'extensions/QCOM/QCOM_shader_framebuffer_fetch_rate.txt',
+ },
+ 'GL_QCOM_texture_foveated' : {
+ 'esnumber' : 293,
+ 'flags' : { 'public' },
+ 'url' : 'extensions/QCOM/QCOM_texture_foveated.txt',
+ },
'GL_QCOM_tiled_rendering' : {
'esnumber' : 70,
'flags' : { 'public' },
@@ -4340,21 +4360,6 @@
'flags' : { 'public' },
'url' : 'extensions/QCOM/QCOM_writeonly_rendering.txt',
},
- 'GL_QCOM_framebuffer_foveated' : {
- 'esnumber' : 273,
- 'flags' : { 'public' },
- 'url' : 'extensions/QCOM/QCOM_framebuffer_foveated.txt',
- },
- 'GL_QCOM_texture_foveated' : {
- 'esnumber' : 293,
- 'flags' : { 'public' },
- 'url' : 'extensions/QCOM/QCOM_texture_foveated.txt',
- },
- 'GL_QCOM_shader_framebuffer_fetch_noncoherent' : {
- 'esnumber' : 277,
- 'flags' : { 'public' },
- 'url' : 'extensions/QCOM/QCOM_shader_framebuffer_fetch_noncoherent.txt',
- },
'GL_REND_screen_coordinates' : {
'number' : 155,
'flags' : { 'public' },
diff --git a/xml/gl.xml b/xml/gl.xml
index 067b3b3..1b36b68 100644
--- a/xml/gl.xml
+++ b/xml/gl.xml
@@ -49090,6 +49090,8 @@
<command name="glFramebufferFetchBarrierQCOM"/>
</require>
</extension>
+ <extension name="GL_QCOM_shader_framebuffer_fetch_rate" supported="gles2">
+ </extension>
<extension name="GL_QCOM_tiled_rendering" supported="gles1|gles2">
<require>
<enum name="GL_COLOR_BUFFER_BIT0_QCOM"/>
