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Tweak Particle Sample #492

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Merged
merged 2 commits into from
Jan 28, 2025
Merged

Tweak Particle Sample #492

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7d721a4
Tweak Particle Sample
greggman Jan 25, 2025
d2f55d0
address comments
greggman Jan 28, 2025
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75 changes: 36 additions & 39 deletions sample/particles/main.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -182,39 +182,30 @@ quadVertexBuffer.unmap();
//////////////////////////////////////////////////////////////////////////////
// Texture
//////////////////////////////////////////////////////////////////////////////
let texture: GPUTexture;
let textureWidth = 1;
let textureHeight = 1;
let numMipLevels = 1;
{
const response = await fetch('../../assets/img/webgpu.png');
const imageBitmap = await createImageBitmap(await response.blob());

// Calculate number of mip levels required to generate the probability map
while (
textureWidth < imageBitmap.width ||
textureHeight < imageBitmap.height
) {
textureWidth *= 2;
textureHeight *= 2;
numMipLevels++;
}
texture = device.createTexture({
size: [imageBitmap.width, imageBitmap.height, 1],
mipLevelCount: numMipLevels,
format: 'rgba8unorm',
usage:
GPUTextureUsage.TEXTURE_BINDING |
GPUTextureUsage.STORAGE_BINDING |
GPUTextureUsage.COPY_DST |
GPUTextureUsage.RENDER_ATTACHMENT,
});
device.queue.copyExternalImageToTexture(
{ source: imageBitmap },
{ texture: texture },
[imageBitmap.width, imageBitmap.height]
);
}
const isPowerOf2 = (v: number) => Math.log2(v) % 1 === 0;
const response = await fetch('../../assets/img/webgpu.png');
const imageBitmap = await createImageBitmap(await response.blob());
assert(imageBitmap.width === imageBitmap.height, 'image must be square');
assert(isPowerOf2(imageBitmap.width), 'image must be a power of 2');

// Calculate number of mip levels required to generate the probability map
const mipLevelCount =
(Math.log2(Math.max(imageBitmap.width, imageBitmap.height)) + 1) | 0;
const texture = device.createTexture({
size: [imageBitmap.width, imageBitmap.height, 1],
mipLevelCount,
format: 'rgba8unorm',
usage:
GPUTextureUsage.TEXTURE_BINDING |
GPUTextureUsage.STORAGE_BINDING |
GPUTextureUsage.COPY_DST |
GPUTextureUsage.RENDER_ATTACHMENT,
});
device.queue.copyExternalImageToTexture(
{ source: imageBitmap },
{ texture: texture },
[imageBitmap.width, imageBitmap.height]
);

//////////////////////////////////////////////////////////////////////////////
// Probability map generation
Expand Down Expand Up @@ -247,22 +238,22 @@ let numMipLevels = 1;
usage: GPUBufferUsage.UNIFORM | GPUBufferUsage.COPY_DST,
});
const buffer_a = device.createBuffer({
size: textureWidth * textureHeight * 4,
size: texture.width * texture.height * 4,
usage: GPUBufferUsage.STORAGE,
});
const buffer_b = device.createBuffer({
size: textureWidth * textureHeight * 4,
size: buffer_a.size,
usage: GPUBufferUsage.STORAGE,
});
device.queue.writeBuffer(
probabilityMapUBOBuffer,
0,
new Int32Array([textureWidth])
new Uint32Array([texture.width])
);
const commandEncoder = device.createCommandEncoder();
for (let level = 0; level < numMipLevels; level++) {
const levelWidth = textureWidth >> level;
const levelHeight = textureHeight >> level;
for (let level = 0; level < texture.mipLevelCount; level++) {
const levelWidth = Math.max(1, texture.width >> level);
const levelHeight = Math.max(1, texture.height >> level);
const pipeline =
level == 0
? probabilityMapImportLevelPipeline.getBindGroupLayout(0)
Expand Down Expand Up @@ -472,3 +463,9 @@ function frame() {
}
configureContext();
requestAnimationFrame(frame);

function assert(cond: boolean, msg = '') {
if (!cond) {
throw new Error(msg);
}
}
29 changes: 13 additions & 16 deletions sample/particles/probabilityMap.wgsl
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Original file line number Diff line number Diff line change
Expand Up @@ -2,17 +2,12 @@ struct UBO {
width : u32,
}

struct Buffer {
weights : array<f32>,
}

@binding(0) @group(0) var<uniform> ubo : UBO;
@binding(1) @group(0) var<storage, read> buf_in : Buffer;
@binding(2) @group(0) var<storage, read_write> buf_out : Buffer;
@binding(1) @group(0) var<storage, read> buf_in : array<f32>;
@binding(2) @group(0) var<storage, read_write> buf_out : array<f32>;
@binding(3) @group(0) var tex_in : texture_2d<f32>;
@binding(3) @group(0) var tex_out : texture_storage_2d<rgba8unorm, write>;


////////////////////////////////////////////////////////////////////////////////
// import_level
//
Expand All @@ -21,9 +16,11 @@ struct Buffer {
////////////////////////////////////////////////////////////////////////////////
@compute @workgroup_size(64)
fn import_level(@builtin(global_invocation_id) coord : vec3u) {
_ = &buf_in;
let offset = coord.x + coord.y * ubo.width;
buf_out.weights[offset] = textureLoad(tex_in, vec2i(coord.xy), 0).w;
_ = &buf_in; // so the bindGroups are similar.
if (all(coord.xy < vec2u(textureDimensions(tex_in)))) {
let offset = coord.x + coord.y * ubo.width;
buf_out[offset] = textureLoad(tex_in, vec2i(coord.xy), 0).w;
}
}

////////////////////////////////////////////////////////////////////////////////
Expand All @@ -40,13 +37,13 @@ fn export_level(@builtin(global_invocation_id) coord : vec3u) {
let dst_offset = coord.x + coord.y * ubo.width;
let src_offset = coord.x*2u + coord.y*2u * ubo.width;

let a = buf_in.weights[src_offset + 0u];
let b = buf_in.weights[src_offset + 1u];
let c = buf_in.weights[src_offset + 0u + ubo.width];
let d = buf_in.weights[src_offset + 1u + ubo.width];
let sum = dot(vec4f(a, b, c, d), vec4f(1.0));
let a = buf_in[src_offset + 0u];
let b = buf_in[src_offset + 1u];
let c = buf_in[src_offset + 0u + ubo.width];
let d = buf_in[src_offset + 1u + ubo.width];
let sum = a + b + c + d;

buf_out.weights[dst_offset] = sum / 4.0;
buf_out[dst_offset] = sum / 4.0;

let probabilities = vec4f(a, a+b, a+b+c, sum) / max(sum, 0.0001);
textureStore(tex_out, vec2i(coord.xy), probabilities);
Expand Down
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