Collision and Simple Physics - Game Coding Complete - page 589

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probably describing most of the readers of this topic, let s discuss this important

integration task.
Note that the code presented in this section is only a tiny part of integrating a phys-
ics SDK into a complete game. The functionality here won

' t get you much past

bouncing balls on a ground plane, so don t expect more than that. The goal is to

show you how a third-party physics system fits into the game architecture presented
in this topic. It

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s up to you to extend this class for additional functionality or use a
different SDK than the one I chose.
It helps to discuss an interface class for a simple physics system. The interface shown
here creates a few objects and manages their movements. If you want to abstract an
entire physics system, you

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' d extend this class quite a lot. Actually, you ' dextendthisinter-

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face and probably create a few new ones. We ll keep it simple for now, just to get you

started. After the interface discussion, we ' ll implement it using the Bullet Physics SDK
available from www.bulletphysics.com, which is available for free under the Zlib license.

class IGamePhysics
{
public:
// Initialization and Maintenance of the Physics World
virtual bool VInitialize()=0;
virtual void VOnUpdate( float deltaSeconds ) = 0;

virtual void VSyncVisibleScene() = 0;

// Initialization of Physics Objects
virtual void VAddSphere(float radius,
WeakActorPtr actor, const Mat4x4& initialTransform,
const std::string& densityStr, const std::string& physicsMaterial)=0;
virtual void VAddBox(const Vec3& dimensions,
WeakActorPtr gameActor, const Mat4x4& initialTransform,
const std::string& densityStr, const std::string& physicsMaterial) = 0;
virtual void VRemoveActor(ActorId id)=0;

// Debugging
virtual void VRenderDiagnostics() = 0;

// Physics world modifiers
virtual void VCreateTrigger(WeakActorPtr gameActor, const Vec3 &pos,
const float dim)=0;
virtual void VApplyForce(const Vec3 &dir, float newtons, ActorId aid)=0;
virtual void VApplyTorque(const Vec3 &dir, float newtons, ActorId aid)=0;
virtual bool VKinematicMove(const Mat4x4 &mat, ActorId aid)=0;

}