WebGL Rendering: How Browsers Became Graphics Engines

Ten years ago, 3D graphics required native apps. Now browsers run AAA-quality games.

Here's how.

The Big Idea

Your GPU has 3000+ cores. WebGL lets JavaScript control them.

Result: Parallel processing for graphics. Thousands of calculations simultaneously.

The Pipeline (Vertices → Pixels in 5 Steps)

1. JavaScript Sets Up Data

const vertices = new Float32Array([
    -1, -1, 0,  // Triangle point 1
     1, -1, 0,  // Point 2
     0,  1, 0   // Point 3
]);

2. Vertex Shader (GPU Program #1)

attribute vec3 position;
uniform mat4 transform;

void main() {
    gl_Position = transform * vec4(position, 1.0);
}

Runs once per vertex. Calculates final position.

3. Rasterization (Hardware Does This)

GPU determines which pixels the triangle covers.

4. Fragment Shader (GPU Program #2)

void main() {
    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);  // Red
}

Runs once per pixel. Calculates color.

5. Display

Pixels appear on screen.

The magic: Steps 2-4 run in parallel on thousands of cores.

Why It's So Fast

CPU rendering (old way):

for each triangle:
    for each pixel it covers:
        calculate color  // Sequential, slow

GPU rendering (WebGL way):

All pixels calculate color simultaneously  // Parallel, fast

Result: 1000x faster.

Three.js Hides the Complexity

Raw WebGL:

• 100+ lines to draw a cube
• Manual matrix math
• Shader compilation code
• Buffer management

Three.js:

const geometry = new THREE.BoxGeometry();
const material = new THREE.MeshBasicMaterial({color: 0x00ff00});
const cube = new THREE.Mesh(geometry, material);
scene.add(cube);

Same result, 4 lines.

What You Can Build

• Data visualizations (millions of data points)
• 3D product configurators
• Browser-based CAD tools
• Particle systems (our Mad Science experiments!)
• Real-time simulations

The Future: WebGPU

WebGL's successor. Even more powerful:

• Compute shaders (general GPU programming)
• Better performance
• Modern API design

Chrome/Firefox support it now.

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Try: three.js examples showcase Related: Our experiments page uses WebGL heavily