Home/ Questions/Q 6715583
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-26T08:37:55+00:00

I am developing an android game with box2d and use a fixed timestep system

  • 0

I am developing an android game with box2d and use a fixed timestep system for advancing the physics.

However as I use this system it requires the box2d positions to be interpolates. I read this article
and have implemented an interpolation method very much like the one in the article.

The method seems to work nicely on the computer but on my phone the positions of objects are very jumpy. There is of course a big frame rate difference between PC and phone, but I think this algorithm should not mind that.

Here is the just of the code if you don’t feel like looking at the article :

void PhysicsSystem::smoothStates_ ()
{
    const float oneMinusRatio = 1.f - fixedTimestepAccumulatorRatio_;

    for (b2Body * b = world_->GetBodyList (); b != NULL; b = b->GetNext ())
    {
        if (b->GetType () == b2_staticBody)
        {
            continue;
        }

        PhysicsComponent & c = PhysicsComponent::b2BodyToPhysicsComponent (* b);
        c.smoothedPosition_ =
            fixedTimestepAccumulatorRatio_ * b->GetPosition () +
            oneMinusRatio * c.previousPosition_;
        c.smoothedAngle_ =
            fixedTimestepAccumulatorRatio_ * b->GetAngle () +
            oneMinusRatio * c.previousAngle_;
    }
}

Does anyone know why my game is acting like this?

Thanks for the help

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    That code in and of itself doesn’t appear to have any issues as compared to the article. You might want to try posting this on https://gamedev.stackexchange.com/ and see if they have any recommendations.

    Alternatively, here is a very well written article about having a semi-fixed time step, and decoupling physics and frame rate, which I imagine could be the problem. It isn’t for Box2D, but reading over it might help you pinpoint the issue with your physics.

    • 0