LIBGDX speeding up a whole game (using box2d)

Question

I was wondering how i can speed up whole game done with libgdx (for example after clicking a button). The way i have in my game is modify a timestep variable used in

world.step(TIMESTEP, VELOCITYITERATIONS, POSITIONITERATIONS);

but im now sure if it's a good idea. If there a any better way to archive that?

Answer 1

When using Box2D you can speed up your game by modifying the physics step. One problem is that you should use a constant steptime. I use the following code below in my games:

private float accumulator = 0;

private void doPhysicsStep(float deltaTime) {
    // fixed time step
    // max frame time to avoid spiral of death (on slow devices)
    float frameTime = Math.min(deltaTime, 0.25f);
    accumulator += frameTime;
    while (accumulator >= Constants.TIME_STEP) {
        WorldManager.world.step(Constants.TIME_STEP, Constants.VELOCITY_ITERATIONS, Constants.POSITION_ITERATIONS);
        accumulator -= Constants.TIME_STEP;
    }
}

This makes sure that your steptime is constant, but it's synchronized with the render loop. You could use that and call it like doPhysicsStep(deltaTime * speedup) (speedup is 1 by default, and maybe 1.5 after a button was pressed). This might probably result in not optimal results, but you could give it a try.

Otherwise you can go the hard way like it was suggested in the comments and invest more time by modifiying every place in your code where it is necessary (all forces need to be modified, which in many cases isn't as trivial as force * speedup, because in the real/physics world, not everything acts linear).