/* Copyright (c) 2007 Scott Lembcke *  * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: *  * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. *  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */struct cpBody;typedef void (*cpBodyVelocityFunc)(struct cpBody *body, cpVect gravity, cpFloat damping, cpFloat dt);typedef void (*cpBodyPositionFunc)(struct cpBody *body, cpFloat dt); typedef struct cpBody{	// *** Integration Functions.	// Function that is called to integrate the body's velocity. (Defaults to cpBodyUpdateVelocity)	cpBodyVelocityFunc velocity_func;		// Function that is called to integrate the body's position. (Defaults to cpBodyUpdatePosition)	cpBodyPositionFunc position_func;		// *** Mass Properties		// Mass and it's inverse.	// Always use cpBodySetMass() whenever changing the mass as these values must agree.	cpFloat m, m_inv;		// Moment of inertia and it's inverse.	// Always use cpBodySetMass() whenever changing the mass as these values must agree.	cpFloat i, i_inv;		// *** Positional Properties		// Linear components of motion (position, velocity, and force)	cpVect p, v, f;		// Angular components of motion (angle, angular velocity, and torque)	// Always use cpBodySetAngle() to set the angle of the body as a and rot must agree.	cpFloat a, w, t;		// Cached unit length vector representing the angle of the body.	// Used for fast vector rotation using cpvrotate().	cpVect rot;		// *** User Definable Fields		// User defined data pointer.	void *data;		// *** Internally Used Fields		// Velocity bias values used when solving penetrations and correcting joints.	cpVect v_bias;	cpFloat w_bias;	//	int active;} cpBody;// Basic allocation/destruction functionscpBody *cpBodyAlloc(void);cpBody *cpBodyInit(cpBody *body, cpFloat m, cpFloat i);cpBody *cpBodyNew(cpFloat m, cpFloat i);void cpBodyDestroy(cpBody *body);void cpBodyFree(cpBody *body);// Setters for some of the special properties (mandatory!)void cpBodySetMass(cpBody *body, cpFloat m);void cpBodySetMoment(cpBody *body, cpFloat i);void cpBodySetAngle(cpBody *body, cpFloat a);//  Modify the velocity of the body so that it will move to the specified absolute coordinates in the next timestep.// Intended for objects that are moved manually with a custom velocity integration function.void cpBodySlew(cpBody *body, cpVect pos, cpFloat dt);// Default Integration functions.void cpBodyUpdateVelocity(cpBody *body, cpVect gravity, cpFloat damping, cpFloat dt);void cpBodyUpdatePosition(cpBody *body, cpFloat dt);// Convert body local to world coordinatesstatic inline cpVectcpBodyLocal2World(cpBody *body, cpVect v){	return cpvadd(body->p, cpvrotate(v, body->rot));}// Convert world to body local coordinatesstatic inline cpVectcpBodyWorld2Local(cpBody *body, cpVect v){	return cpvunrotate(cpvsub(v, body->p), body->rot);}// Apply an impulse (in world coordinates) to the body.static inline voidcpBodyApplyImpulse(cpBody *body, cpVect j, cpVect r){	body->v = cpvadd(body->v, cpvmult(j, body->m_inv));	body->w += body->i_inv*cpvcross(r, j);}// Not intended for external use. Used by cpArbiter.c and cpJoint.c.static inline voidcpBodyApplyBiasImpulse(cpBody *body, cpVect j, cpVect r){	body->v_bias = cpvadd(body->v_bias, cpvmult(j, body->m_inv));	body->w_bias += body->i_inv*cpvcross(r, j);}// Zero the forces on a body.void cpBodyResetForces(cpBody *body);// Apply a force (in world coordinates) to a body.void cpBodyApplyForce(cpBody *body, cpVect f, cpVect r);// Apply a damped spring force between two bodies.void cpDampedSpring(cpBody *a, cpBody *b, cpVect anchr1, cpVect anchr2, cpFloat rlen, cpFloat k, cpFloat dmp, cpFloat dt);//int cpBodyMarkLowEnergy(cpBody *body, cpFloat dvsq, int max);