CODEWITHSUNDEEP
javaandroidlibgdxbox2d
as lan
as lan

Reputation: 37

Infinite vertical world

I am created two bodies in Box2d, they are: Player and Platform;

I wanted to create game like Doodle Jump, but I don't know how to create "infinite world with generating platforms";

There is my code where I am creating Array:

buckets = new Array<Bucket>();

for(int i=1;i<BUCKET_COUNT;i++){
    buckets.add(new Bucket(W/2,BUCKET_MARGIN*i, world));
}

And this code where I am "Trying" to change position of each platform when camera position is change:

for(Bucket bucket : buckets){
        if(cam.position.y - (cam.viewportHeight/2) > bucket.getBody().getPosition().y + 22/PPM){
            bucket.repos(W/2,bucket.getBody().getPosition().y + BUCKET_MARGIN);
        }
    }

It works! But it changes last platform position to very far bottom:

Upvotes: 0

Views: 219

Answers (1)

Louis Langholtz
Louis Langholtz

Reputation: 3123

Regarding how to create an infinite world?

Use the world instance shift origin method. In the Box2D 2.3.2 C++ library code, this is the b2World::ShiftOrigin(const b2Vec2& newOrigin) method. Here's an excerpt of this method's declaration along with its documentation:

/// Shift the world origin. Useful for large worlds.
/// The body shift formula is: position -= newOrigin
/// @param newOrigin the new origin with respect to the old origin
void ShiftOrigin(const b2Vec2& newOrigin);

In Java, you should be able to find a similar interface method.

With shift origin you keep the viewport to the physics world centered on (or near) the physical world origin (of 0, 0). This is basically the practical means of accomplishing what Yevhen Danchenko suggested in the comments.

A reason for using this is that the implementation of floating-point arithmetic which Box2D relies on, is itself not infinitely wide ranging nor infinitely accurate. So shifting things helps keep things closer to the origin where the floating-point values are more accurate and keeps things from going off the range of practically usable values assuming that you'll only ever be showing a limited range of x and y values.

Upvotes: 2

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