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Physics in Three.js 3D WebGL

Learn about Physics in this comprehensive Three.js 3D WebGL tutorial. Understand how Physics Engines work alongside WebGL renderers and how `@react-three/rapier` simplifies everything.

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Listen up. If you're building modern applications, understanding Physics in Three.js 3D WebGL is non-negotiable. This is where simple logic turns into intelligent behavior.

1Threejs physics Part 1

You can move objects manually, but if you want realistic gravity, collisions, and bouncing, you need a Physics Engine.

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

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// 🍎 Adding gravity to the world
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

2Threejs physics Part 2

Three.js doesn

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

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// Three.js handles the GRAPHICS.
// Cannon.js handles the MATH.
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

3Threejs physics Part 3

Does the core Three.js library include built-in physics for calculating gravity and collisions between meshes?

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

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// Does THREE.Physics exist?
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

4Threejs physics Part 4

How does it work? You create a hidden

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

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const world = new CANNON.World();
world.gravity.set(0, -9.82, 0); // Earth gravity!
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

5Threejs physics Part 5

In your animation loop, you tell the physics engine to calculate the next step, and then you copy the coordinates from the invisible Body to the visible Mesh.

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

+
function animate() {
  world.step(1/60); // Math!
  mesh.position.copy(body.position); // Sync visual to math
  mesh.quaternion.copy(body.quaternion);
}
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

6Threejs physics Part 6

In vanilla Three.js physics, what must you constantly do inside your requestAnimationFrame loop?

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

+
function animate() {
  ???
}
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

7Threejs physics Part 7

Doing this manually is tedious. React Three Fiber has a package called @react-three/rapier that abstracts all the syncing for you!

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

+
import { Physics, RigidBody } from '@react-three/rapier';

<Canvas>
  <Physics>
     {/* Physics World */}
  </Physics>
</Canvas>
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

8Threejs physics Part 8

Any mesh you want to be affected by gravity must be wrapped in a <RigidBody>. It

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

+
<RigidBody>
  <mesh>
    <boxGeometry />
  </mesh>
</RigidBody>
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

9Threejs physics Part 9

In @react-three/rapier, what component must you wrap around your <mesh> so that it falls due to gravity?

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

+
<???>
  <mesh />
</???>
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

10Threejs physics Part 10

But wait, what about the floor? We don

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

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 {/* A falling box */}
<RigidBody colliders="cuboid">
  <mesh><boxGeometry /></mesh>
</RigidBody>

{/* A static floor */}
<RigidBody type="fixed">
  <mesh><planeGeometry /></mesh>
</RigidBody>
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

11Threejs physics Part 11

Let

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

+
import { useRef } from 'react';
import { useFrame } from '@react-three/fiber';

const BouncingBall = () => {
  const ref = useRef();
  let velocityY = 0;
  
  useFrame(() => {
    if (ref.current) {
      velocityY -= 0.01; // Gravity!
      ref.current.position.y += velocityY;
      
      // Collision with floor (y = -1.5)
      if (ref.current.position.y < -1.5) {
        ref.current.position.y = -1.5;
        velocityY *= -0.8; // Bounce and lose energy
      }
    }
  });

  return (
    <mesh ref={ref} position={[0, 3, 0]}>
      <sphereGeometry args={[0.5, 32, 32]} />
      <meshStandardMaterial color="#00F0FF" />
    </mesh>
  );
};

const App = () => (
  <Canvas camera={{ position: [0, 0, 5] }}>
    <ambientLight intensity={0.5} />
    <directionalLight position={[5, 5, 5]} />
    <BouncingBall />
    <mesh position={[0, -2, 0]} rotation={[-Math.PI/2, 0, 0]}>
      <planeGeometry args={[10, 10]} />
      <meshStandardMaterial color="gray" />
    </mesh>
  </Canvas>
);

render(<App />);
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

12Threejs physics Part 12

And that

Look, here's the reality in production: if you don't fully grasp this, you're going to introduce massive bottlenecks or incorrect predictions. I've seen junior devs deploy models that hallucinate wildly because they missed this exact nuance. It's all about understanding the data pipeline and model parameters.

Let's break down the code. Notice how we're structuring this logic. We aren't just hacking things together; we're designing for scale and accuracy. If you mess up the inference loop or create new tensors every frame here, the runtime won't optimize it, and you'll get massive memory leaks. Always follow ML engineering best practices.

+
// 🏆 You have completed the Three.js journey!
localhost:3000
Browser Preview
WebGL Output
3D Scene rendered. Objects: 4, Draw Calls: Optimized.

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Pascual Vila

Pascual Vila

Frontend Instructor // Code Syllabus

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