WebGL EXT_shader_framebuffer_fetch Extension Rejected Specification

Name

EXT_shader_framebuffer_fetch

Contact

WebGL working group (public_webgl 'at' khronos.org)

Contributors

PlayCanvas, Snap Inc

Version

Last modified date: February 01, 2022
Revision: 2

Number

WebGL extension #XYZ

Dependencies

Written against the WebGL API 1.0 specification.

Overview

This extension exposes the EXT_shader_framebuffer_fetch functionality to WebGL.

There are no WebGL-specific behavioral changes.

Consult the above extension for documentation, issues and new functions and enumerants.

When this extension is enabled:

• It provides a mechanism whereby a fragment shader may read existing framebuffer data as input.
• Prior to fragment shading, if GL_EXT_shader_framebuffer_fetch is enabled, gl_LastFragData[] is populated with the value last written to the framebuffer at the same (x,y,sample) position.
• If EXT_shader_framebuffer_fetch_non_coherent is supported, a call to FramebufferFetchBarrierEXT(void) can be made to ensure gl_LastFragData[] is populated with fragment data drawn before the barrier.

IDL

    [Exposed=(Window,Worker), LegacyNoInterfaceObject]
    interface EXT_shader_framebuffer_fetch {
    };

    [Exposed=(Window,Worker), LegacyNoInterfaceObject]
    interface EXT_shader_framebuffer_fetch_non_coherent {
      undefined FramebufferFetchBarrierEXT(void);
    };
  

Sample Code

    void main(){
        gl_FragColor = gl_LastFragData[0];
    }
    

Revision History

Revision 1, 2020/05/22

• Initial revision.

Revision 2, 2022/02/01

• Moved to "Rejected". Recommend pursuing this functionality in WebGPU instead.