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Merged
merged 6 commits into from
Sep 25, 2025
Merged

Add Primitive Picking sample #539

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411e08e
Primitive Picking sample
toji Sep 23, 2025
8051691
Fix lint errors
toji Sep 23, 2025
b6b9535
Address feedback from Gregg
toji Sep 23, 2025
5f35c34
More consistent WGSL formatting
toji Sep 23, 2025
22f1503
Address feedback from Francois
toji Sep 24, 2025
2d82e0f
Update sample/primitivePicking/main.ts
toji Sep 25, 2025
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14 changes: 14 additions & 0 deletions sample/primitivePicking/computePickPrimitive.wgsl
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Original file line number Diff line number Diff line change
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struct Frame {
viewProjectionMatrix : mat4x4f,
invViewProjectionMatrix : mat4x4f,
pickCoord: vec2f,
pickedPrimitive: u32,
}
@group(0) @binding(0) var<storage, read_write> frame : Frame;
@group(0) @binding(1) var primitiveTex: texture_2d<u32>;

@compute @workgroup_size(1)
fn main() {
let texel = vec2u(frame.pickCoord);
frame.pickedPrimitive = textureLoad(primitiveTex, texel, 0).x;
}
37 changes: 37 additions & 0 deletions sample/primitivePicking/fragmentForwardRendering.wgsl
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enable primitive_index;

struct Frame {
viewProjectionMatrix : mat4x4f,
invViewProjectionMatrix : mat4x4f,
pickCoord: vec2f,
pickedPrimitive: u32,
}
@group(0) @binding(1) var<uniform> frame : Frame;

struct PassOutput {
@location(0) color : vec4f,
@location(1) primitive : u32,
}

@fragment
fn main(
@location(0) fragNormal: vec3f,
@builtin(primitive_index) primIndex: u32
) -> PassOutput {
let lightDirection = normalize(vec3f(4, 10, 6));
let light = dot(normalize(fragNormal), lightDirection) * 0.5 + 0.5;
let surfaceColor = vec4f(0.8, 0.8, 0.8, 1.0);

var output : PassOutput;

// Highlight the primitive if it's the selected one, otherwise shade normally.
if (primIndex+1 == frame.pickedPrimitive) {
output.color = vec4f(1.0, 1.0, 0.0, 1.0);
} else {
output.color = vec4f(surfaceColor.xyz * light, surfaceColor.a);
}

// Adding one to each primitive so that 0 can mean "nothing picked"
output.primitive = primIndex+1;
return output;
}
14 changes: 14 additions & 0 deletions sample/primitivePicking/fragmentPrimitivesDebugView.wgsl
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@group(0) @binding(0) var primitiveTex: texture_2d<u32>;

@fragment
fn main(
@builtin(position) coord : vec4f
) -> @location(0) vec4f {
let primitiveIndex = textureLoad(primitiveTex, vec2i(floor(coord.xy)), 0).x;
var result : vec4f;
result.r = f32(primitiveIndex % 8) / 8;
result.g = f32((primitiveIndex / 8) % 8) / 8;
result.b = f32((primitiveIndex / 64) % 8) / 8;
result.a = 1.0;
return result;
}
40 changes: 40 additions & 0 deletions sample/primitivePicking/index.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<title>webgpu-samples: primitivePicking</title>
<!-- WebGPUCompatibilityMode origin token for https://webgpu.github.io expiring April 21, 2026 -->
<meta
http-equiv="origin-trial"
content="Aktu7041jFm00ls336/bRinubASRzg1tPs4wxXOZkF1uP0LaIURinGC7ti0Vf352Q9OKFL1siRfpptLjNIKpKQcAAABheyJvcmlnaW4iOiJodHRwczovL3dlYmdwdS5naXRodWIuaW86NDQzIiwiZmVhdHVyZSI6IldlYkdQVUNvbXBhdGliaWxpdHlNb2RlIiwiZXhwaXJ5IjoxNzc2NzI5NjAwfQ=="
/>
<!-- WebGPUCompatibilityMode origin token for http://localhost:8080 expiring April 21, 2026 -->
<meta
http-equiv="origin-trial"
content="AqW27Ayelg5vbcAaYcweU+sLjZq5r6idHCWU4MJgnkP1YBgmOMqazdGuakSnGylTkyA/bRHkCJZFdfYjFlylOgAAAABaeyJvcmlnaW4iOiJodHRwOi8vbG9jYWxob3N0OjgwODAiLCJmZWF0dXJlIjoiV2ViR1BVQ29tcGF0aWJpbGl0eU1vZGUiLCJleHBpcnkiOjE3NzY3Mjk2MDB9"
/>
<style>
:root {
color-scheme: light dark;
}
html, body {
margin: 0; /* remove default margin */
height: 100%; /* make body fill the browser window */
display: flex;
place-content: center center;
}
canvas {
width: 600px;
height: 600px;
max-width: 100%;
display: block;
}
</style>
<script defer src="main.js" type="module"></script>
<script defer type="module" src="../../js/iframe-helper.js"></script>
</head>
<body>
<canvas></canvas>
</body>
</html>
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