ToyMaker: Physics System

What is it?

The ToyMaker::PhysicsSystem is responsible for applying physics updates each simulation frame to all eligible entities, especially those that are tagged with ToyMaker::PhysicsState::MODE_DYNAMIC. Additionally, it watches for and reports collision events detected between physics entities during each simulation frame.

In order for an entity to be eligible for the physics system, it must hold the following components:

• ToyMaker::ObjectBounds – Data defining a volume on which the physics system will operate.
• ToyMaker::AxisAlignedBounds – Derived from ToyMaker::ObjectBounds, this is used primarily during the physics systems broad phase collision detection stage to limit the number of collision checks performed.
• ToyMaker::PhysicsState – A collection of properties defining the behaviour of the object during physics updates.

Important API

Mainly, aside from setting object positions through ToyMaker::ObjectBounds rather than ToyMaker::Placement, one interacts with the physics system through the ToyMaker::PhysicsState component.

• ToyMaker::PhysicsState::mTraits – Which kind of physics updates this object is subscribed to, and how it responds to collision events.
  • ToyMaker::PhysicsState::MODE_DYNAMIC – This object responds to both position updates derived from its velocity and velocity updates derived from external forces.
  • ToyMaker::PhysicsState::MODE_KINEMATIC – This object does not respond to velocity updates through forces but does update object position & orientation based on velocity.
  • ToyMaker::PhysicsState::MODE_STATIC – This object doesn't respond to velocity or force updates, and is expected to stay in place more or less throughout its life.
  • ToyMaker::PhysicsState::COLLISION_SEPARATE – This object is configured to separate from other objects when collisions are detected.
  • ToyMaker::PhysicsState::COLLISION_SIGNAL – This object will signal on collision with or separation from other objects.
• ToyMaker::PhysicsState::mMassInverse & ToyMaker::PhysicsState::mRotationalInertiaInverse – Properties defining the resistance of this object to translational and rotational motion.
• ToyMaker::PhysicsState::mForce & ToyMaker::PhysicsState::mTorque – The sum external translational force and torque acting on this object for this physics update.
• ToyMaker::PhysicsState::mVelocity & ToyMaker::PhysicsState::mAngularVelocity – The current velocity of this object, in terms of translation and rotation respectively.
• ToyMaker::PhysicsState::mCoefficientFrictionDynamic & ToyMaker::PhysicsState::mCoefficientFrictionStatic – The object's resistance to motion relative to another object at its point of contact when it is moving and when it is stationary respectively.
• ToyMaker::PhysicsState::mCoefficientRestitution – The total kinetic energy preserved by two colliding objects after the collision as a fraction of their kinetic energy before collision.

Practical examples of this system may be found under Examples/.

Why does it exist?

It enables the creation of games and applications that require more complex physical interactions between objects.