Collisions by Gravity – BabylonJS Series part 9

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Did you ever play to an FPS (First Person Shooter) game? We are to simulate the same camera movements: the camera is on the floor, in collision with the ground and any objects.


Final result

How can I do this ?

To replicate this movement, we have to do this in 3 simple steps:

1 – Define and apply gravity

The first thing to do is to define our gravity vector, defining the G force. In a classic world, on earth, the direction of the force of gravity is down on Y axis, but be free to change it!

scene.gravity = new BABYLON.Vector3(0, -9.81, 0);

Gravity can be applied to any camera that you have defined previously in your code.

camera.applyGravity = true;

2 – Define ellipsoid

An important step is now to define the ellipsoid around our camera. This ellipsoid is representing our player’s dimensions: a collision event will be raised when a mesh will be in contact with this ellipsoid, preventing camera to be too close to this mesh:


This ellipsoid is the one by default, but changing values will make you taller, bigger, or smaller, thinner, depending of the axis.

//Set the ellipsoid around the camera (e.g. your player's size)
camera.ellipsoid = new BABYLON.Vector3(1, 1, 1);

3 – Apply collision

Finally, when those previous elements are ready, we just have to declare that we are interested in collisions:

// Enable Collisions
scene.collisionsEnabled = true;

And what are the meshes which could be in collision with our camera:

ground.checkCollisions = true;
box.checkCollisions = true;

That’s it!

Now, your camera is going to fall on y-axis until it collide our ground.