Real Physics Enabled Racing Game

Questions
24

I’ve taken the bit and parts and ported them over one by one. If I remember correctly, very few, if any, changes are needed to make it work.

In the castRay function of your raycaster, you simply put:

 rayCallback.m_collisionFilterMask = collisionFilterMask;
 rayCallback.m_collisionFilterGroup = collisionFilterGroup;

Before you do the rayTest.
So between setting the result callback and calling the rayTest function. Then it’s automatically handled.

Then you just need a way of setting your mask and group. The best way of doing this is to create a function that takes two ints, one for the mask and one for the group, and do collisionFilterMask = BIT(int)
Then export this function in the idl.

A cool feature of the SuperTuxKart project as well is auto-stabilization of the vehicle when airborne.
You can give it a Vector3 telling it which direction is up (0,1,0), and an int or float as an impulse to automatically stabilize the vehicle, so it hits the ground correctly.

        btVector3 kart_up    = getChassisWorldTransform().getBasis().getColumn(1);
        //btVector3 terrain_up = btVector3(0, 1, 0);
        // Length of axis depends on the angle - i.e. the further awat
        // the kart is from being upright, the larger the applied impulse
        // will be, resulting in fast changes when the kart is on its
        // side, but not overcompensating (and therefore shaking) when
        // the kart is not much away from being upright.
        btVector3 axis = kart_up.cross(terrain_up);

        // To avoid the kart going backwards/forwards (or rolling sideways),
        // set the pitch/roll to 0 before applying the 'straightening' impulse.
        // TODO: make this works if gravity is changed.
        btVector3 av = m_chassisBody->getAngularVelocity();
        av.setX(0);
        av.setZ(0);
        m_chassisBody->setAngularVelocity(av);
        // Give a nicely balanced feeling for rebalancing the kart
        m_chassisBody->applyTorqueImpulse(axis * stabImpulse);
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