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WebGPURenderer: Make MSAA with MRT work with WebGL backend. #31228

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Merged
merged 2 commits into from
Jun 6, 2025
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WebGPURenderer: Make MSAA with MRT work with WebGL backend. #31228

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192a456
WebGPURenderer: Make MSAA with MRT work with WebGL backend.
Mugen87 Jun 5, 2025
693396e
E2E: Update screenshots.
Mugen87 Jun 5, 2025
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Binary file modified examples/screenshots/webgpu_custom_fog_background.jpg
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7 changes: 0 additions & 7 deletions src/nodes/display/PassNode.js
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Original file line number Diff line number Diff line change
Expand Up @@ -586,13 +586,6 @@ class PassNode extends TempNode {

this.renderTarget.samples = this.options.samples === undefined ? renderer.samples : this.options.samples;

// TODO: Disable MSAA for WebGL backend for now
if ( renderer.backend.isWebGLBackend === true ) {

this.renderTarget.samples = 0;

}

this.renderTarget.texture.type = renderer.getColorBufferType();

return this.scope === PassNode.COLOR ? this.getTextureNode() : this.getLinearDepthNode();
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48 changes: 45 additions & 3 deletions src/renderers/webgl-fallback/WebGLBackend.js
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Original file line number Diff line number Diff line change
Expand Up @@ -563,15 +563,40 @@ class WebGLBackend extends Backend {
}

const msaaFrameBuffer = renderTargetContextData.msaaFrameBuffer;
const msaaRenderbuffers = renderTargetContextData.msaaRenderbuffers;

const textures = renderContext.textures;
const isMRT = textures.length > 1;

state.bindFramebuffer( gl.READ_FRAMEBUFFER, msaaFrameBuffer );
state.bindFramebuffer( gl.DRAW_FRAMEBUFFER, fb );

if ( isMRT ) {

// blitFramebuffer() can only copy/resolve the first color attachment of a framebuffer. When using MRT,
// the engine temporarily removes all attachments and then configures each attachment for the resolve.

for ( let i = 0; i < textures.length; i ++ ) {

gl.framebufferRenderbuffer( gl.READ_FRAMEBUFFER, gl.COLOR_ATTACHMENT0 + i, gl.RENDERBUFFER, null );
gl.framebufferTexture2D( gl.DRAW_FRAMEBUFFER, gl.COLOR_ATTACHMENT0 + i, gl.TEXTURE_2D, null, 0 );

}

}

for ( let i = 0; i < textures.length; i ++ ) {

// TODO Add support for MRT
if ( isMRT ) {

// configure attachment for resolve

const { textureGPU } = this.get( textures[ i ] );

gl.framebufferRenderbuffer( gl.READ_FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, msaaRenderbuffers[ i ] );
gl.framebufferTexture2D( gl.DRAW_FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, textureGPU, 0 );

}

if ( renderContext.scissor ) {

Expand Down Expand Up @@ -601,6 +626,21 @@ class WebGLBackend extends Backend {

}

if ( isMRT ) {

// restore attachments

for ( let i = 0; i < textures.length; i ++ ) {

const { textureGPU } = this.get( textures[ i ] );

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Not sure but I think you should bind the MSAA FBO and the FBO here @Mugen87:

state.bindFramebuffer( _gl.FRAMEBUFFER, msaaFrameBuffer);

gl.framebufferRenderbuffer( gl.READ_FRAMEBUFFER, gl.COLOR_ATTACHMENT0 + i, gl.RENDERBUFFER, msaaRenderbuffers[ i ] );

state.bindFramebuffer( _gl.FRAMEBUFFER, fb);

gl.framebufferTexture2D( gl.DRAW_FRAMEBUFFER, gl.COLOR_ATTACHMENT0 + i, gl.TEXTURE_2D, textureGPU, 0 );

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@RenaudRohlinger RenaudRohlinger Jun 5, 2025 •
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also unbind before the loop:

state.bindFramebuffer( _gl.READ_FRAMEBUFFER, null );
state.bindFramebuffer( _gl.DRAW_FRAMEBUFFER, null );

and rebind after:

state.bindFramebuffer( gl.READ_FRAMEBUFFER, msaaFrameBuffer );

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Unfortunately, that does not do any difference. In fact, it seems some bindings in WebGLRenderer are redundant. A single bind of the draw and read buffer at the beginning of the blit process should be sufficinet. Removing all these bindings in WebGLRenderer does not break webgl_multiple_rendertargets.

gl.framebufferRenderbuffer( gl.READ_FRAMEBUFFER, gl.COLOR_ATTACHMENT0 + i, gl.RENDERBUFFER, msaaRenderbuffers[ i ] );
gl.framebufferTexture2D( gl.DRAW_FRAMEBUFFER, gl.COLOR_ATTACHMENT0 + i, gl.TEXTURE_2D, textureGPU, 0 );

}

}

} else if ( renderTarget.resolveDepthBuffer === false && renderTargetContextData.framebuffers ) {

const fb = renderTargetContextData.framebuffers[ renderContext.getCacheKey() ];
Expand Down Expand Up @@ -2095,8 +2135,6 @@ class WebGLBackend extends Backend {

}

state.drawBuffers( descriptor, fb );

}

const depthStyle = stencilBuffer ? gl.DEPTH_STENCIL_ATTACHMENT : gl.DEPTH_ATTACHMENT;
Expand Down Expand Up @@ -2271,6 +2309,8 @@ class WebGLBackend extends Backend {

}

gl.bindRenderbuffer( gl.RENDERBUFFER, null );

renderTargetContextData.msaaFrameBuffer = msaaFb;
renderTargetContextData.msaaRenderbuffers = msaaRenderbuffers;

Expand Down Expand Up @@ -2298,6 +2338,8 @@ class WebGLBackend extends Backend {

}

state.drawBuffers( descriptor, fb );

}

state.bindFramebuffer( gl.FRAMEBUFFER, currentFrameBuffer );
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2 changes: 2 additions & 0 deletions src/renderers/webgl-fallback/utils/WebGLTextureUtils.js
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Expand Up @@ -1021,6 +1021,8 @@ class WebGLTextureUtils {

}

gl.bindRenderbuffer( gl.RENDERBUFFER, null );

}

/**
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