godot/servers/physics/joints_sw.cpp

/*************************************************************************/
/*  joints_sw.cpp                                                        */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2016 Juan Linietsky, Ariel Manzur.                 */
/*                                                                       */
/* 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:                                             */
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/* 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  */
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/*************************************************************************/
#include "joints_sw.h"
#include "space_sw.h"

#if 0

//based on chipmunk joint constraints

/* 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.
 */

static inline real_t k_scalar(Body2DSW *a,Body2DSW *b,const Vector2& rA, const Vector2& rB, const Vector2& n) {


	real_t value=0;


	{
		value+=a->get_inv_mass();
		real_t rcn = rA.cross(n);
		value+=a->get_inv_inertia() * rcn * rcn;
	}

	if (b) {

		value+=b->get_inv_mass();
		real_t rcn = rB.cross(n);
		value+=b->get_inv_inertia() * rcn * rcn;
	}

	return value;

}


bool PinJoint2DSW::setup(float p_step) {

	Space2DSW *space = A->get_space();
	ERR_FAIL_COND_V(!space,false;)
	rA = A->get_transform().xform(anchor_A);
	rB = B?B->get_transform().xform(anchor_B):anchor_B;

	Vector2 delta = rB - rA;

	rA-= A->get_transform().get_origin();
	if (B)
		rB-=B->get_transform().get_origin();


	real_t jdist = delta.length();
	correct=false;
	if (jdist==0)
		return false; // do not correct

	correct=true;

	n = delta / jdist;

	// calculate mass normal
	mass_normal = 1.0f/k_scalar(A, B, rA, rB, n);

	// calculate bias velocity
	//real_t maxBias = joint->constraint.maxBias;
	bias = -(get_bias()==0?space->get_constraint_bias():get_bias())*(1.0/p_step)*(jdist-dist);
	bias = CLAMP(bias, -get_max_bias(), +get_max_bias());

	// compute max impulse
	jn_max = get_max_force() * p_step;

	// apply accumulated impulse
	Vector2 j = n * jn_acc;
	A->apply_impulse(rA,-j);
	if (B)
		B->apply_impulse(rB,j);

	return true;
}


static inline Vector2
relative_velocity(Body2DSW *a, Body2DSW *b, Vector2 rA, Vector2 rB){
	Vector2 sum = a->get_linear_velocity() -rA.tangent() * a->get_angular_velocity();
	if (b)
		return (b->get_linear_velocity() -rB.tangent() * b->get_angular_velocity()) - sum;
	else
		return -sum;
}

static inline real_t
normal_relative_velocity(Body2DSW *a, Body2DSW *b, Vector2 rA, Vector2 rB, Vector2 n){
	return relative_velocity(a, b, rA, rB).dot(n);
}


void PinJoint2DSW::solve(float p_step){

	if (!correct)
		return;

	Vector2 ln = n;

	// compute relative velocity
	real_t vrn = normal_relative_velocity(A,B, rA, rB, ln);

	// compute normal impulse
	real_t jn = (bias - vrn)*mass_normal;
	real_t jnOld = jn_acc;
	jn_acc = CLAMP(jnOld + jn,-jn_max,jn_max); //cpfclamp(jnOld + jn, -joint->jnMax, joint->jnMax);
	jn = jn_acc - jnOld;

	Vector2 j = jn*ln;

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

}


PinJoint2DSW::PinJoint2DSW(const Vector2& p_pos,Body2DSW* p_body_a,Body2DSW* p_body_b) : Joint2DSW(_arr,p_body_b?2:1) {

	A=p_body_a;
	B=p_body_b;
	anchor_A = p_body_a->get_inv_transform().xform(p_pos);
	anchor_B = p_body_b?p_body_b->get_inv_transform().xform(p_pos):p_pos;

	jn_acc=0;
	dist=0;

	p_body_a->add_constraint(this,0);
	if (p_body_b)
		p_body_b->add_constraint(this,1);

}

PinJoint2DSW::~PinJoint2DSW() {

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

}

//////////////////////////////////////////////
//////////////////////////////////////////////
//////////////////////////////////////////////


static inline void
k_tensor(Body2DSW *a, Body2DSW *b, Vector2 r1, Vector2 r2, Vector2 *k1, Vector2 *k2)
{
	// calculate mass matrix
	// If I wasn't lazy and wrote a proper matrix class, this wouldn't be so gross...
	real_t k11, k12, k21, k22;
	real_t m_sum = a->get_inv_mass() + b->get_inv_mass();

	// start with I*m_sum
	k11 = m_sum; k12 = 0.0f;
	k21 = 0.0f;  k22 = m_sum;

	// add the influence from r1
	real_t a_i_inv = a->get_inv_inertia();
	real_t r1xsq =  r1.x * r1.x * a_i_inv;
	real_t r1ysq =  r1.y * r1.y * a_i_inv;
	real_t r1nxy = -r1.x * r1.y * a_i_inv;
	k11 += r1ysq; k12 += r1nxy;
	k21 += r1nxy; k22 += r1xsq;

	// add the influnce from r2
	real_t b_i_inv = b->get_inv_inertia();
	real_t r2xsq =  r2.x * r2.x * b_i_inv;
	real_t r2ysq =  r2.y * r2.y * b_i_inv;
	real_t r2nxy = -r2.x * r2.y * b_i_inv;
	k11 += r2ysq; k12 += r2nxy;
	k21 += r2nxy; k22 += r2xsq;

	// invert
	real_t determinant = k11*k22 - k12*k21;
	ERR_FAIL_COND(determinant== 0.0);

	real_t det_inv = 1.0f/determinant;
	*k1 = Vector2( k22*det_inv, -k12*det_inv);
	*k2 = Vector2(-k21*det_inv,  k11*det_inv);
}

static _FORCE_INLINE_ Vector2
mult_k(const Vector2& vr, const Vector2 &k1, const Vector2 &k2)
{
	return Vector2(vr.dot(k1), vr.dot(k2));
}

bool GrooveJoint2DSW::setup(float p_step) {


	// calculate endpoints in worldspace
	Vector2 ta = A->get_transform().xform(A_groove_1);
	Vector2 tb = A->get_transform().xform(A_groove_2);
	Space2DSW *space=A->get_space();

	// calculate axis
	Vector2 n = -(tb - ta).tangent().normalized();
	real_t d = ta.dot(n);

	xf_normal = n;
	rB = B->get_transform().basis_xform(B_anchor);

	// calculate tangential distance along the axis of rB
	real_t td = (B->get_transform().get_origin() + rB).cross(n);
	// calculate clamping factor and rB
	if(td <= ta.cross(n)){
		clamp = 1.0f;
		rA = ta - A->get_transform().get_origin();
	} else if(td >= tb.cross(n)){
		clamp = -1.0f;
		rA = tb - A->get_transform().get_origin();
	} else {
		clamp = 0.0f;
		//joint->r1 = cpvsub(cpvadd(cpvmult(cpvperp(n), -td), cpvmult(n, d)), a->p);
		rA =  ((-n.tangent() * -td) + n*d) - A->get_transform().get_origin();
	}

	// Calculate mass tensor
	k_tensor(A, B, rA, rB, &k1, &k2);

	// compute max impulse
	jn_max = get_max_force() * p_step;

	// calculate bias velocity
//	cpVect delta = cpvsub(cpvadd(b->p, joint->r2), cpvadd(a->p, joint->r1));
//	joint->bias = cpvclamp(cpvmult(delta, -joint->constraint.biasCoef*dt_inv), joint->constraint.maxBias);


	Vector2 delta = (B->get_transform().get_origin() +rB) - (A->get_transform().get_origin() + rA);
	gbias=(delta*-(get_bias()==0?space->get_constraint_bias():get_bias())*(1.0/p_step)).clamped(get_max_bias());

	// apply accumulated impulse
	A->apply_impulse(rA,-jn_acc);
	B->apply_impulse(rB,jn_acc);

	correct=true;
	return true;
}

void GrooveJoint2DSW::solve(float p_step){


	// compute impulse
	Vector2 vr = relative_velocity(A, B, rA,rB);

	Vector2 j = mult_k(gbias-vr, k1, k2);
	Vector2 jOld = jn_acc;
	j+=jOld;

	jn_acc = (((clamp * j.cross(xf_normal)) > 0) ? j : xf_normal.project(j)).clamped(jn_max);

	j = jn_acc - jOld;

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


GrooveJoint2DSW::GrooveJoint2DSW(const Vector2& p_a_groove1,const Vector2& p_a_groove2, const Vector2& p_b_anchor, Body2DSW* p_body_a,Body2DSW* p_body_b) : Joint2DSW(_arr,2) {

	A=p_body_a;
	B=p_body_b;

	A_groove_1 = A->get_inv_transform().xform(p_a_groove1);
	A_groove_2 = A->get_inv_transform().xform(p_a_groove2);
	B_anchor=B->get_inv_transform().xform(p_b_anchor);
	A_groove_normal = -(A_groove_2 - A_groove_1).normalized().tangent();

	A->add_constraint(this,0);
	B->add_constraint(this,1);

}

GrooveJoint2DSW::~GrooveJoint2DSW() {

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


//////////////////////////////////////////////
//////////////////////////////////////////////
//////////////////////////////////////////////


bool DampedSpringJoint2DSW::setup(float p_step) {

	rA = A->get_transform().basis_xform(anchor_A);
	rB = B->get_transform().basis_xform(anchor_B);

	Vector2 delta = (B->get_transform().get_origin() + rB) - (A->get_transform().get_origin() + rA) ;
	real_t dist = delta.length();

	if (dist)
		n=delta/dist;
	else
		n=Vector2();

	real_t k = k_scalar(A, B, rA, rB, n);
	n_mass = 1.0f/k;

	target_vrn = 0.0f;
	v_coef = 1.0f - Math::exp(-damping*(p_step)*k);

	// apply spring force
	real_t f_spring = (rest_length - dist) * stiffness;
	Vector2 j = n * f_spring*(p_step);

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


	return true;
}

void DampedSpringJoint2DSW::solve(float p_step) {

	// compute relative velocity
	real_t vrn = normal_relative_velocity(A, B, rA, rB, n) - target_vrn;

	// compute velocity loss from drag
	// not 100% certain this is derived correctly, though it makes sense
	real_t v_damp = -vrn*v_coef;
	target_vrn = vrn + v_damp;
	Vector2 j=n*v_damp*n_mass;

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

}

void DampedSpringJoint2DSW::set_param(Physics2DServer::DampedStringParam p_param, real_t p_value) {

	switch(p_param) {

		case Physics2DServer::DAMPED_STRING_REST_LENGTH: {

			rest_length=p_value;
		} break;
		case Physics2DServer::DAMPED_STRING_DAMPING: {

			damping=p_value;
		} break;
		case Physics2DServer::DAMPED_STRING_STIFFNESS: {

			stiffness=p_value;
		} break;
	}

}

real_t DampedSpringJoint2DSW::get_param(Physics2DServer::DampedStringParam p_param) const{

	switch(p_param) {

		case Physics2DServer::DAMPED_STRING_REST_LENGTH: {

			return rest_length;
		} break;
		case Physics2DServer::DAMPED_STRING_DAMPING: {

			return damping;
		} break;
		case Physics2DServer::DAMPED_STRING_STIFFNESS: {

			return stiffness;
		} break;
	}

	ERR_FAIL_V(0);
}


DampedSpringJoint2DSW::DampedSpringJoint2DSW(const Vector2& p_anchor_a,const Vector2& p_anchor_b, Body2DSW* p_body_a,Body2DSW* p_body_b) : Joint2DSW(_arr,2) {


	A=p_body_a;
	B=p_body_b;
	anchor_A = A->get_inv_transform().xform(p_anchor_a);
	anchor_B = B->get_inv_transform().xform(p_anchor_b);

	rest_length=p_anchor_a.distance_to(p_anchor_b);
	stiffness=20;
	damping=1.5;


	A->add_constraint(this,0);
	B->add_constraint(this,1);

}

DampedSpringJoint2DSW::~DampedSpringJoint2DSW() {

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

}


#endif