Dmitry Sergeev
73 lines
2.6 KiB
WebGPU Shading Language
73 lines
2.6 KiB
WebGPU Shading Language
// 13-step grayscale bars (Y 64..940 in even 73-code steps), Rec.709, 10-bit
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// Y'CbCr, packed as v210 (4:2:2). Chroma neutral.
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// One work-item per 16-byte block = 6 pixels (6 Y + 3 Cb + 3 Cr).
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struct Params {
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width: u32,
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height: u32,
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frame: u32, // animation tick (0,1,2,... per generated frame), NOT the raw grain index
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_pad0: u32,
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};
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@group(0) @binding(0) var<storage, read_write> out: array<u32>;
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@group(0) @binding(1) var<uniform> params: Params;
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fn bar_index(px: u32) -> u32 {
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return min((px * 13u) / params.width, 12u);
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}
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@compute @workgroup_size(64)
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fn main(@builtin(global_invocation_id) gid: vec3<u32>) {
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let block = gid.x;
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let blocks_per_row = (params.width + 5u) / 6u;
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let total = blocks_per_row * params.height;
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if (block >= total) {
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return;
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}
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let y_tab = array<u32, 13>(64u, 137u, 210u, 283u, 356u, 429u, 502u, 575u, 648u, 721u, 794u, 867u, 940u);
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let x = (block % blocks_per_row) * 6u;
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let py = block / blocks_per_row;
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// Moving square: horizontal oscillation around screen center.
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// frame is a small tick; converting the huge raw grain index here
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// would destroy f32 precision and freeze the motion.
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let centerX = f32(params.width) / 2.0;
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let centerY = f32(params.height) / 2.0;
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let fps = 25.0;
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let t = f32(params.frame) / fps;
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const squareSize = 150u;
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let half = f32(squareSize) / 2.0;
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let offsetPixels = sin(t * 0.5) * (centerX - half);
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let sq_x_min = centerX - half + offsetPixels;
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let sq_x_max = centerX + half + offsetPixels;
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let sq_y_min = centerY - half;
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let sq_y_max = centerY + half;
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let py_f = f32(py);
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var y: array<u32, 6>;
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var cb: array<u32, 6>;
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var cr: array<u32, 6>;
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for (var i = 0u; i < 6u; i++) {
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let b = bar_index(x + i);
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let px = f32(x + i);
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y[i] = y_tab[b];
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cb[i] = 512u;
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cr[i] = 512u;
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if (px >= sq_x_min && px < sq_x_max && py_f >= sq_y_min && py_f < sq_y_max) {
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y[i] = 1004u - y[i];
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cb[i] = 1024u - cb[i];
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cr[i] = 1024u - cr[i];
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}
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}
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// v210 word layout, chroma co-sited with luma samples 0/2/4:
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// w0 = Cb0|Y0<<10|Cr0<<20; w1 = Y1|Cb2<<10|Y2<<20;
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// w2 = Cr2|Y3<<10|Cb4<<20; w3 = Y4|Cr4<<10|Y5<<20
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out[block * 4u + 0u] = (cb[0] & 0x3FFu) | ((y[0] & 0x3FFu) << 10u) | ((cr[0] & 0x3FFu) << 20u);
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out[block * 4u + 1u] = (y[1] & 0x3FFu) | ((cb[2] & 0x3FFu) << 10u) | ((y[2] & 0x3FFu) << 20u);
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out[block * 4u + 2u] = (cr[2] & 0x3FFu) | ((y[3] & 0x3FFu) << 10u) | ((cb[4] & 0x3FFu) << 20u);
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out[block * 4u + 3u] = (y[4] & 0x3FFu) | ((cr[4] & 0x3FFu) << 10u) | ((y[5] & 0x3FFu) << 20u);
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}
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