nuclear@0: #include <stdio.h>
nuclear@0: #include <float.h>
nuclear@0: #include "cloth.h"
nuclear@0: #include "object.h"
nuclear@0: #include "opengl.h"
nuclear@0: 
nuclear@0: Cloth::Cloth()
nuclear@0: {
nuclear@0: 	mass = 1.0;
nuclear@0: 	elast = 0.8;
nuclear@0: 	spring_k = 1.0;
nuclear@0: 	grav = Vector3(0, -9, 0);
nuclear@0: }
nuclear@0: 
nuclear@0: void Cloth::create_rect(int x, int y, float width, float height)
nuclear@0: {
nuclear@0: 	int num = x * y;
nuclear@0: 	float dx = width / (float)x;
nuclear@0: 	float dy = height / (float)y;
nuclear@0: 
nuclear@0: 	masses.resize(num);
nuclear@0: 	conn.resize(num);
nuclear@0: 	for(int i=0; i<num; i++) {
nuclear@0: 		conn[i].resize(num);
nuclear@0: 	}
nuclear@0: 
nuclear@0: 	int idx = 0;
nuclear@0: 	for(int i=0; i<y; i++) {
nuclear@0: 		for(int j=0; j<x; j++) {
nuclear@0: 			// position the mass
nuclear@0: 			masses[idx].pos.x = (float)j * dx - width / 2.0;
nuclear@0: 			masses[idx].pos.y = 0;
nuclear@0: 			masses[idx].pos.z = (float)i * dy - height / 2.0;
nuclear@0: 			masses[idx].fixed = i == 0 && (j == 0 || j == x - 1);	// XXX debug hack
nuclear@0: 			++idx;
nuclear@0: 		}
nuclear@0: 	}
nuclear@0: 
nuclear@0: 	idx = 0;
nuclear@0: 	for(int i=0; i<y; i++) {
nuclear@0: 		for(int j=0; j<x; j++) {
nuclear@0: 			// not connected to itself
nuclear@0: 			conn[idx][idx] = -1;
nuclear@0: 
nuclear@0: 			// connect node to its neighbors
nuclear@0: 			for(int ni=0; ni<5; ni++) {
nuclear@0: 				for(int nj=0; nj<5; nj++) {
nuclear@0: 					int nx = j + nj - 2;
nuclear@0: 					int ny = i + ni - 2;
nuclear@0: 
nuclear@0: 					if(!nx && !ny) continue;
nuclear@0: 					if(nx < 0 || nx >= x || ny < 0 || ny >= y) continue;
nuclear@0: 
nuclear@0: 					int nidx = ny * x + nx;
nuclear@0: 					float dist = length(masses[idx].pos - masses[nidx].pos);
nuclear@0: 
nuclear@0: 					conn[idx][nidx] = conn[nidx][idx] = dist;
nuclear@0: 				}
nuclear@0: 			}
nuclear@0: 
nuclear@0: 			++idx;
nuclear@0: 		}
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: void Cloth::transform(const Matrix4x4 &xform)
nuclear@0: {
nuclear@0: 	for(size_t i=0; i<masses.size(); i++) {
nuclear@0: 		masses[i].pos = masses[i].pos * xform;
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: void Cloth::add_collider(Object *o)
nuclear@0: {
nuclear@0: 	colliders.push_back(o);
nuclear@0: }
nuclear@0: 
nuclear@0: void Cloth::step(float dt)
nuclear@0: {
nuclear@0: 	int num_masses = (int)masses.size();
nuclear@0: 
nuclear@0: 	for(int i=0; i<num_masses; i++) {
nuclear@0: 		if(masses[i].fixed) continue;
nuclear@0: 
nuclear@0: 		Vector3 newpos = masses[i].pos + masses[i].vel * dt;
nuclear@0: 
nuclear@0: 		Vector3 force = grav + forces;
nuclear@0: 
nuclear@0: 		for(int j=0; j<num_masses; j++) {
nuclear@0: 			if(conn[i][j] <= 0.0) continue;	// skip unconnected
nuclear@0: 
nuclear@0: 			Vector3 dir = masses[j].pos - masses[i].pos;
nuclear@0: 			float dist = length(dir);
nuclear@0: 
nuclear@0: 			// apply an impulse based on the displacement from the original state
nuclear@0: 			force += dir * (dist - conn[i][j]) * spring_k;
nuclear@0: 		}
nuclear@0: 
nuclear@0: 		// update the velocity by integrating the accumulation of all forces
nuclear@0: 		masses[i].vel += force * dt;
nuclear@0: 
nuclear@0: 		Ray ray;
nuclear@0: 		ray.origin = masses[i].pos;
nuclear@0: 		ray.dir = newpos - masses[i].pos;
nuclear@0: 
nuclear@0: 		HitPoint pt;
nuclear@0: 		if(find_collision(ray, &pt)) {
nuclear@0: 			newpos = pt.pos;
nuclear@0: 			masses[i].vel = reflect(masses[i].vel, pt.normal) * elast;	// TODO collider elasticity
nuclear@0: 		}
nuclear@0: 		masses[i].pos = newpos;
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: bool Cloth::find_collision(const Ray &ray, HitPoint *hit) const
nuclear@0: {
nuclear@0: 	HitPoint nearest;
nuclear@0: 	nearest.obj = 0;
nuclear@0: 	nearest.t = FLT_MAX;
nuclear@0: 
nuclear@0: 	for(size_t i=0; i<colliders.size(); i++) {
nuclear@0: 		if(colliders[i]->intersect(ray, hit) && hit->t < nearest.t) {
nuclear@0: 			nearest = *hit;
nuclear@0: 		}
nuclear@0: 	}
nuclear@0: 
nuclear@0: 	if(nearest.obj) {
nuclear@0: 		*hit = nearest;
nuclear@0: 		return true;
nuclear@0: 	}
nuclear@0: 	return false;
nuclear@0: }
nuclear@0: 
nuclear@0: void Cloth::draw() const
nuclear@0: {
nuclear@0: 	glPushAttrib(GL_ENABLE_BIT);
nuclear@0: 
nuclear@0: 	glPointSize(7.0);
nuclear@0: 	glEnable(GL_POINT_SMOOTH);
nuclear@0: 
nuclear@0: 	glEnable(GL_BLEND);
nuclear@0: 	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
nuclear@0: 
nuclear@0: 	// draw masses
nuclear@0: 	glBegin(GL_POINTS);
nuclear@0: 	for(size_t i=0; i<masses.size(); i++) {
nuclear@0: 		if(masses[i].fixed) {
nuclear@0: 			glColor3f(1, 0, 0);
nuclear@0: 		} else {
nuclear@0: 			glColor3f(1, 0.4, 0.2);
nuclear@0: 		}
nuclear@0: 		glVertex3f(masses[i].pos.x, masses[i].pos.y, masses[i].pos.z);
nuclear@0: 	}
nuclear@0: 	glEnd();
nuclear@0: 
nuclear@0: 	glBlendFunc(GL_SRC_ALPHA, GL_ONE);
nuclear@0: 
nuclear@0: 	// draw neighbor connection lines
nuclear@0: 	glBegin(GL_LINES);
nuclear@0: 	glColor4f(0, 1, 0, 0.25);
nuclear@0: 
nuclear@0: 	for(size_t i=0; i<masses.size(); i++) {
nuclear@0: 		for(size_t j=0; j<masses.size(); j++) {
nuclear@0: 			if(i == j || conn[i][j] <= 0.0) continue;
nuclear@0: 
nuclear@0: 			glVertex3f(masses[i].pos.x, masses[i].pos.y, masses[i].pos.z);
nuclear@0: 			glVertex3f(masses[j].pos.x, masses[j].pos.y, masses[j].pos.z);
nuclear@0: 		}
nuclear@0: 	}
nuclear@0: 	glEnd();
nuclear@0: 
nuclear@0: 	glPopAttrib();
nuclear@0: }