godot/servers/physics/body_pair_sw.cpp

/*************************************************************************/
/*  body_pair_sw.cpp                                                     */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                 */
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/* a copy of this software and associated documentation files (the       */
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#include "body_pair_sw.h"
#include "collision_solver_sw.h"
#include "space_sw.h"


/*
#define NO_ACCUMULATE_IMPULSES
#define NO_SPLIT_IMPULSES

#define NO_FRICTION
*/

#define NO_TANGENTIALS
/* BODY PAIR */


//#define ALLOWED_PENETRATION 0.01
#define RELAXATION_TIMESTEPS 3
#define MIN_VELOCITY 0.0001

void BodyPairSW::_contact_added_callback(const Vector3& p_point_A,const Vector3& p_point_B,void *p_userdata) {

	BodyPairSW* pair  = (BodyPairSW*)p_userdata;
	pair->contact_added_callback(p_point_A,p_point_B);

}

void BodyPairSW::contact_added_callback(const Vector3& p_point_A,const Vector3& p_point_B) {

	// check if we already have the contact

	//Vector3 local_A = A->get_inv_transform().xform(p_point_A);
	//Vector3 local_B = B->get_inv_transform().xform(p_point_B);

	Vector3 local_A = A->get_inv_transform().basis.xform(p_point_A);
	Vector3 local_B = B->get_inv_transform().basis.xform(p_point_B-offset_B);



	int new_index = contact_count;

	ERR_FAIL_COND( new_index >= (MAX_CONTACTS+1) );

	Contact contact;

	contact.acc_normal_impulse=0;
	contact.acc_bias_impulse=0;
	contact.acc_tangent_impulse=Vector3();
	contact.local_A=local_A;
	contact.local_B=local_B;
	contact.normal=(p_point_A-p_point_B).normalized();



	// attempt to determine if the contact will be reused
	real_t contact_recycle_radius=space->get_contact_recycle_radius();

	for (int i=0;i<contact_count;i++) {

		Contact& c = contacts[i];
		if (
		c.local_A.distance_squared_to( local_A ) < (contact_recycle_radius*contact_recycle_radius) &&
		c.local_B.distance_squared_to( local_B ) < (contact_recycle_radius*contact_recycle_radius) ) {

				contact.acc_normal_impulse=c.acc_normal_impulse;
				contact.acc_bias_impulse=c.acc_bias_impulse;
				contact.acc_tangent_impulse=c.acc_tangent_impulse;
				new_index=i;
				break;
		}
	}

	// figure out if the contact amount must be reduced to fit the new contact

	if (new_index == MAX_CONTACTS) {

		// remove the contact with the minimum depth

		int least_deep=-1;
		float min_depth=1e10;

		for (int i=0;i<=contact_count;i++) {

			Contact& c = (i==contact_count)?contact:contacts[i];
			Vector3 global_A = A->get_transform().basis.xform(c.local_A);
			Vector3 global_B = B->get_transform().basis.xform(c.local_B)+offset_B;

			Vector3 axis = global_A - global_B;
			float depth = axis.dot( c.normal );

			if (depth<min_depth) {

				min_depth=depth;
				least_deep=i;
			}
		}

		ERR_FAIL_COND(least_deep==-1);

		if (least_deep < contact_count) { //replace the last deep contact by the new one

			contacts[least_deep]=contact;
		}

		return;
	}

	contacts[new_index]=contact;

	if (new_index==contact_count) {

		contact_count++;
	}

}

void BodyPairSW::validate_contacts() {

	//make sure to erase contacts that are no longer valid

	real_t contact_max_separation=space->get_contact_max_separation();
	for (int i=0;i<contact_count;i++) {

		Contact& c = contacts[i];

		Vector3 global_A = A->get_transform().basis.xform(c.local_A);
		Vector3 global_B = B->get_transform().basis.xform(c.local_B)+offset_B;
		Vector3 axis = global_A - global_B;
		float depth = axis.dot( c.normal );

		if (depth < -contact_max_separation || (global_B + c.normal * depth - global_A).length() > contact_max_separation) {
			// contact no longer needed, remove


			if ((i+1) < contact_count) {
				// swap with the last one
				SWAP( contacts[i], contacts[ contact_count-1 ] );

			}

			i--;
			contact_count--;
		}
	}
}

bool BodyPairSW::setup(float p_step) {


	offset_B = B->get_transform().get_origin() - A->get_transform().get_origin();

	validate_contacts();

	Vector3 offset_A = A->get_transform().get_origin();
	Transform xform_Au = Transform(A->get_transform().basis,Vector3());
	Transform xform_A = xform_Au * A->get_shape_transform(shape_A);

	Transform xform_Bu = B->get_transform();
	xform_Bu.origin-=offset_A;
	Transform xform_B = xform_Bu * B->get_shape_transform(shape_B);

	ShapeSW *shape_A_ptr=A->get_shape(shape_A);
	ShapeSW *shape_B_ptr=B->get_shape(shape_B);

	bool collided = CollisionSolverSW::solve_static(shape_A_ptr,xform_A,shape_B_ptr,xform_B,_contact_added_callback,this,&sep_axis);
	this->collided=collided;

	if (!collided)
		return false;


	//cannot collide
	if (A->has_exception(B->get_self()) || B->has_exception(A->get_self()) || (A->get_mode()<=PhysicsServer::BODY_MODE_KINEMATIC && B->get_mode()<=PhysicsServer::BODY_MODE_KINEMATIC)) {
		return false;
	}

	real_t max_penetration = space->get_contact_max_allowed_penetration();

	float bias = 0.3f;

	if (shape_A_ptr->get_custom_bias() || shape_B_ptr->get_custom_bias()) {

		if (shape_A_ptr->get_custom_bias()==0)
			bias=shape_B_ptr->get_custom_bias();
		else if (shape_B_ptr->get_custom_bias()==0)
			bias=shape_A_ptr->get_custom_bias();
		else
			bias=(shape_B_ptr->get_custom_bias()+shape_A_ptr->get_custom_bias())*0.5;
	}


	real_t inv_dt = 1.0/p_step;

	for(int i=0;i<contact_count;i++) {

		Contact &c = contacts[i];
		c.active=false;

		Vector3 global_A = xform_Au.xform(c.local_A);
		Vector3 global_B = xform_Bu.xform(c.local_B);


		real_t depth = c.normal.dot(global_A - global_B);

		if (depth<=0) {
			c.active=false;
			continue;
		}

		c.active=true;

		int gather_A = A->can_report_contacts();
		int gather_B = B->can_report_contacts();

		c.rA = global_A;
		c.rB = global_B-offset_B;

		// contact query reporting...
#if 0
		if (A->get_body_type() == PhysicsServer::BODY_CHARACTER)
			static_cast<CharacterBodySW*>(A)->report_character_contact( global_A, global_B, B );
		if (B->get_body_type() == PhysicsServer::BODY_CHARACTER)
			static_cast<CharacterBodySW*>(B)->report_character_contact( global_B, global_A, A );
		if (A->has_contact_query())
			A->report_contact( global_A, global_B, B );
		if (B->has_contact_query())
			B->report_contact( global_B, global_A, A );
#endif

		if (A->can_report_contacts()) {
			Vector3 crB = A->get_angular_velocity().cross( c.rA ) + A->get_linear_velocity();
			A->add_contact(global_A,-c.normal,depth,shape_A,global_B,shape_B,B->get_instance_id(),B->get_self(),crB);
		}

		if (B->can_report_contacts()) {
			Vector3 crA = A->get_angular_velocity().cross( c.rB ) + A->get_linear_velocity();
			B->add_contact(global_B,c.normal,depth,shape_B,global_A,shape_A,A->get_instance_id(),A->get_self(),crA);
		}

		c.active=true;

		// Precompute normal mass, tangent mass, and bias.
		Vector3 inertia_A = A->get_inv_inertia_tensor().xform( c.rA.cross( c.normal ) );
		Vector3 inertia_B = B->get_inv_inertia_tensor().xform( c.rB.cross( c.normal ) );
		real_t kNormal = A->get_inv_mass() + B->get_inv_mass();
		kNormal += c.normal.dot( inertia_A.cross(c.rA ) ) + c.normal.dot( inertia_B.cross( c.rB ));
		c.mass_normal = 1.0f / kNormal;

#if 1
		c.bias = -bias * inv_dt * MIN(0.0f, -depth + max_penetration);

#else
		if (depth > max_penetration) {
			c.bias = (depth - max_penetration) * (1.0/(p_step*(1.0/RELAXATION_TIMESTEPS)));
		} else {
			float approach = -0.1f * (depth - max_penetration) / (CMP_EPSILON + max_penetration);
			approach = CLAMP( approach, CMP_EPSILON, 1.0 );
			c.bias = approach * (depth - max_penetration) * (1.0/p_step);
		}
#endif
		c.depth=depth;

		Vector3 j_vec = c.normal * c.acc_normal_impulse + c.acc_tangent_impulse;
		A->apply_impulse( c.rA, -j_vec );
		B->apply_impulse( c.rB, j_vec );
		c.acc_bias_impulse=0;
		Vector3 jb_vec = c.normal * c.acc_bias_impulse;
		A->apply_bias_impulse( c.rA, -jb_vec );
		B->apply_bias_impulse( c.rB, jb_vec );

	}

	return true;
}

void BodyPairSW::solve(float p_step) {

	if (!collided)
		return;


	for(int i=0;i<contact_count;i++) {

		Contact &c = contacts[i];
		if (!c.active)
			continue;

		c.active=false; //try to deactivate, will activate itself if still needed

		//bias impule

		Vector3 crbA = A->get_biased_angular_velocity().cross( c.rA );
		Vector3 crbB = B->get_biased_angular_velocity().cross( c.rB );
		Vector3 dbv = B->get_biased_linear_velocity() + crbB - A->get_biased_linear_velocity() - crbA;

		real_t vbn = dbv.dot(c.normal);

		if (Math::abs(-vbn+c.bias)>MIN_VELOCITY) {

			real_t jbn = (-vbn + c.bias)*c.mass_normal;
			real_t jbnOld = c.acc_bias_impulse;
			c.acc_bias_impulse = MAX(jbnOld + jbn, 0.0f);

			Vector3 jb = c.normal * (c.acc_bias_impulse - jbnOld);


			A->apply_bias_impulse(c.rA,-jb);
			B->apply_bias_impulse(c.rB, jb);

			c.active=true;
		}


		Vector3 crA = A->get_angular_velocity().cross( c.rA );
		Vector3 crB = B->get_angular_velocity().cross( c.rB );
		Vector3 dv = B->get_linear_velocity() + crB - A->get_linear_velocity() - crA;

		//normal impule
		real_t vn = dv.dot(c.normal);

		if (Math::abs(vn)>MIN_VELOCITY) {

			real_t bounce=0;
			real_t jn = (-bounce -vn)*c.mass_normal;
			real_t jnOld = c.acc_normal_impulse;
			c.acc_normal_impulse = MAX(jnOld + jn, 0.0f);


			Vector3 j =c.normal * (c.acc_normal_impulse - jnOld);


			A->apply_impulse(c.rA,-j);
			B->apply_impulse(c.rB, j);

			c.active=true;
		}

		//friction impule

		real_t friction = A->get_friction() * B->get_friction();

		Vector3 lvA = A->get_linear_velocity() + A->get_angular_velocity().cross( c.rA );
		Vector3 lvB = B->get_linear_velocity() + B->get_angular_velocity().cross( c.rB );

		Vector3 dtv = lvB - lvA;
		real_t tn = c.normal.dot(dtv);

		// tangential velocity
		Vector3 tv = dtv - c.normal * tn;
		real_t tvl = tv.length();

		if (tvl > MIN_VELOCITY) {

			tv /= tvl;

			Vector3 temp1 = A->get_inv_inertia_tensor().xform( c.rA.cross( tv ) );
			Vector3 temp2 = B->get_inv_inertia_tensor().xform( c.rB.cross( tv ) );

			real_t t = -tvl /
				(A->get_inv_mass() + B->get_inv_mass() + tv.dot(temp1.cross(c.rA) + temp2.cross(c.rB)));

			Vector3 jt = t * tv;


			Vector3 jtOld = c.acc_tangent_impulse;
			c.acc_tangent_impulse += jt;

			real_t fi_len = c.acc_tangent_impulse.length();
			real_t jtMax = c.acc_normal_impulse * friction;

			if (fi_len > CMP_EPSILON && fi_len > jtMax) {

				c.acc_tangent_impulse*=jtMax / fi_len;
			}

			jt = c.acc_tangent_impulse - jtOld;


			A->apply_impulse( c.rA, -jt );
			B->apply_impulse( c.rB, jt );

			c.active=true;

		}


	}

}





BodyPairSW::BodyPairSW(BodySW *p_A, int p_shape_A,BodySW *p_B, int p_shape_B) : ConstraintSW(_arr,2) {

	A=p_A;
	B=p_B;
	shape_A=p_shape_A;
	shape_B=p_shape_B;
	space=A->get_space();
	A->add_constraint(this,0);
	B->add_constraint(this,1);
	contact_count=0;
	collided=false;

}


BodyPairSW::~BodyPairSW() {

	A->remove_constraint(this);
	B->remove_constraint(this);

}