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<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Plasma-Arc: WGPU Experiment</title>
</head>

<body>
    <canvas></canvas>
    <script type="module">
        import { mat4 } from 'https://webgpufundamentals.org/3rdparty/wgpu-matrix.module.js';
        import { fetchShaderCode, generateGlyphTextureAtlas } from './utility.js';
        import { CONFIG } from './config.js';
        import { CANVAS, CTX, COLORS, RENDER_PASS_DESCRIPTOR } from './constants.js';

        const canvas = document.querySelector('canvas');
        const context = canvas.getContext('webgpu');
        const presentationFormat = navigator.gpu.getPreferredCanvasFormat();
        let device, pipeline, vertexBuffer, indexBuffer, uniformBuffer, texture, sampler, bindGroup;

        async function main() {
            const adapter = await navigator.gpu?.requestAdapter();
            device = await adapter?.requestDevice();
            if (!device) return alert('WebGPU support required');

            context.configure({ device, format: presentationFormat });

            const shaderCode = await fetchShaderCode('shaders.wgsl');
            const module = device.createShaderModule({ label: 'textured quad shaders', code: shaderCode });

            const glyphCanvas = generateGlyphTextureAtlas(CANVAS, CTX, CONFIG);
            document.body.appendChild(glyphCanvas).style.backgroundColor = '#222';

            const vertexSize = CONFIG.floatsPerVertex * 4;
            const vertexBufferSize = CONFIG.maxGlyphs * CONFIG.vertsPerGlyph * vertexSize;
            vertexBuffer = device.createBuffer({ label: 'vertices', size: vertexBufferSize, usage: GPUBufferUsage.VERTEX | GPUBufferUsage.COPY_DST });
            indexBuffer = device.createBuffer({ label: 'indices', size: CONFIG.maxGlyphs * CONFIG.vertsPerGlyph * 4, usage: GPUBufferUsage.INDEX | GPUBufferUsage.COPY_DST });

            const indices = Array.from({ length: CONFIG.maxGlyphs * 6 }, (_, i) => {
                const ndx = Math.floor(i / 6) * 4;
                return (i % 6 < 3 ? [ndx, ndx + 1, ndx + 2] : [ndx + 2, ndx + 1, ndx + 3])[i % 3];
            });
            device.queue.writeBuffer(indexBuffer, 0, new Uint32Array(indices));

            const { vertexData, numGlyphs, width, height } = generateGlyphVerticesForText('Hello\nworld!\nText in\nWebGPU!', COLORS, glyphCanvas);
            device.queue.writeBuffer(vertexBuffer, 0, vertexData);
            
            pipeline = device.createRenderPipeline({
                label: 'textured quad pipeline',
                layout: 'auto',
                vertex: {
                    module,
                    entryPoint: 'vs',
                    buffers: [
                        {
                            arrayStride: vertexSize,
                            attributes: [
                                { shaderLocation: 0, offset: 0, format: 'float32x2' },  // pos
                                { shaderLocation: 1, offset: 8, format: 'float32x2' },  // tex
                                { shaderLocation: 2, offset: 16, format: 'float32x4' }  // col
                            ],
                        },
                    ],
                },
                fragment: {
                    module,
                    entryPoint: 'fs',
                    targets: [{
                        format: presentationFormat,
                        blend: {
                            color: { srcFactor: 'one', dstFactor: 'one-minus-src-alpha', operation: 'add' },
                            alpha: { srcFactor: 'one', dstFactor: 'one-minus-src-alpha', operation: 'add' }
                        },
                    }],
                },
            });

            texture = createTextureFromSource(device, glyphCanvas);
            sampler = device.createSampler({ minFilter: 'linear', magFilter: 'linear' });
            uniformBuffer = device.createBuffer({ label: 'uniforms for quad', size: CONFIG.uniformBufferSize, usage: GPUBufferUsage.UNIFORM | GPUBufferUsage.COPY_DST });

            const uniformValues = new Float32Array(CONFIG.uniformBufferSize / 4);
            const matrix = uniformValues.subarray(0, 16);

            bindGroup = device.createBindGroup({
                layout: pipeline.getBindGroupLayout(0),
                entries: [
                    { binding: 0, resource: sampler },
                    { binding: 1, resource: texture.createView() },
                    { binding: 2, resource: { buffer: uniformBuffer } },
                ],
            });

            function render(time) {
                time *= CONFIG.time.phase;
                const fov = 60 * Math.PI / 180;
                const aspect = canvas.clientWidth / canvas.clientHeight;
                const projectionMatrix = mat4.perspective(fov, aspect, CONFIG.render.zNear, CONFIG.render.zFar);
                const viewMatrix = mat4.lookAt([0, 0, 5], [0, 0, 0], [0, 1, 0]);
                const viewProjectionMatrix = mat4.multiply(projectionMatrix, viewMatrix);
                RENDER_PASS_DESCRIPTOR.colorAttachments[0].view = context.getCurrentTexture().createView();
                const encoder = device.createCommandEncoder();
                const pass = encoder.beginRenderPass(RENDER_PASS_DESCRIPTOR);
                pass.setPipeline(pipeline);
                mat4.rotateY(viewProjectionMatrix, time, matrix);
                mat4.translate(matrix, [-width / 2, -height / 2, 0], matrix);
                device.queue.writeBuffer(uniformBuffer, 0, uniformValues);
                pass.setBindGroup(0, bindGroup);
                pass.setVertexBuffer(0, vertexBuffer);
                pass.setIndexBuffer(indexBuffer, 'uint32');
                pass.drawIndexed(numGlyphs * 6);
                pass.end();
                device.queue.submit([encoder.finish()]);
                requestAnimationFrame(render);
            }

            requestAnimationFrame(render);
        }

        function generateGlyphVerticesForText(s, COLORS, glyphCanvas) {
            const vertexData = new Float32Array(CONFIG.maxGlyphs * CONFIG.floatsPerVertex * CONFIG.vertsPerGlyph);
            const glyphUVWidth = CONFIG.glyphWidth / glyphCanvas.width;
            const glyphUVHeight = CONFIG.glyphHeight / glyphCanvas.height;
            let offset = 0, x0 = 0, y0 = 0, x1 = 1, y1 = 1, width = 0;
            let colorNdx = 0;

            const addVertex = (x, y, u, v, color) => {
                vertexData.set([x, y, u, v, ...color], offset);
                offset += 8;
            };

            for (let i = 0; i < s.length; ++i) {
                const c = s.charCodeAt(i);
                if (c >= 33) {
                    const cIndex = c - 33;
                    const glyphX = cIndex % CONFIG.glyphsAcrossTexture;
                    const glyphY = Math.floor(cIndex / CONFIG.glyphsAcrossTexture);
                    const u0 = glyphX * CONFIG.glyphWidth / glyphCanvas.width;
                    const v1 = glyphY * CONFIG.glyphHeight / glyphCanvas.height;
                    const u1 = u0 + glyphUVWidth;
                    const v0 = v1 + glyphUVHeight;
                    width = Math.max(x1, width);
                    addVertex(x0, y0, u0, v0, COLORS[colorNdx]);
                    addVertex(x1, y0, u1, v0, COLORS[colorNdx]);
                    addVertex(x0, y1, u0, v1, COLORS[colorNdx]);
                    addVertex(x1, y1, u1, v1, COLORS[colorNdx]);
                } else {
                    colorNdx = (colorNdx + 1) % COLORS.length;
                    if (c === 10) { // Newline
                        x0 = 0; x1 = 1; y0--; y1 = y0 + 1;
                        continue;
                    }
                }
                x0 += 0.55; x1 = x0 + 1;
            }
            return { vertexData, numGlyphs: offset / CONFIG.floatsPerVertex, width, height: y1 };
        }

        function createTextureFromSource(device, source) {
            const texture = device.createTexture({
                format: 'rgba8unorm',
                size: [source.width, source.height],
                usage: GPUTextureUsage.TEXTURE_BINDING | GPUTextureUsage.COPY_DST | GPUTextureUsage.RENDER_ATTACHMENT,
            });

            device.queue.copyExternalImageToTexture(
                { source, flipY: true },
                { texture, premultipliedAlpha: true },
                { width: source.width, height: source.height }
            );

            return texture;
        }

        main();
    </script>
</body>

</html>