engine/docs/en/physics/overall.md

order, title, type, label

order	title	type	label
1	Overview of Physics	Physics	Physics

The physics engine is a very important part of the game engine. The industry generally adopts PhysX to introduce related functions. However, for lightweight scenarios, PhysX makes the final application size very large, exceeding the limits of these projects. Galacean is designed based on multiple backends. On one hand, it compiles PhysX.js through WebAssembly; on the other hand, it also provides a lightweight physics engine. Both are consistent in API design. Users only need to choose a specific physics backend when initializing the engine. It can meet the needs of various scenarios such as lightweight applications and heavyweight games. For the overall design of the physics components, you can refer to the Wiki.

For scenarios that need to use various physics components and InputManager that require Raycast picking, the physics engine needs to be initialized before use. Currently, the Galacean engine provides two built-in physics engine backend implementations:

• physics-lite
• physics-physx

Developers can set the physics backend in the Project Settings panel opened from the Main Menu interface.

If initializing the engine through a script, you only need to pass the physics backend object into the Engine:

import {LitePhysics} from "@galacean/engine-physics-lite";

const engine = await WebGLEngine.create({
  canvas: htmlCanvas,
  physics: new LitePhysics(),
});

Loading and Initializing the PhysX Version of the Physics Engine

import { PhysXPhysics } from "@galacean/engine-physics-physx";

const engine = await WebGLEngine.create({
  canvas: htmlCanvas,
  physics: new PhysXPhysics(),
});

Choosing a Physics Backend

Choosing a physics backend needs to consider three factors: functionality, performance, and package size:

1. Functionality: For complete physics engine functionality and high-performance physics simulation, it is recommended to choose the PhysX backend. The Lite backend only supports collision detection.
2. Performance: PhysX will automatically downgrade to pure JavaScript code on platforms that do not support WebAssembly, so performance will also decrease. However, due to the built-in data structures for scene search, the performance is still better than the Lite backend.
3. Package Size: Choosing the PhysX backend will additionally introduce nearly 2.5mb of wasm files (the size of the pure JavaScript version is similar), increasing the package size while reducing the application's initialization speed.