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@roxlu
Created Dec 27, 2011
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Parallel Transport Frames - TEST
//--------------------------------------------------------------
void testApp::setup(){
ofSetFrameRate(60);
ofSetVerticalSync(true);
ofBackground(33);
donnie.create(125);
donnie.si.drawUsingQuads();
//renderer.addSceneItem(donnie.si);
renderer.translate(0,0,10);
// just creating some particles and springs.
Particle* a = ps.createParticle(Vec3(-5,9,0));
Particle* b = ps.createParticle(Vec3(-5,8.8,0));
Particle* c = ps.createParticle(Vec3(-5,8.6,0));
Particle* d = ps.createParticle(Vec3(-5,8.4,0));
a->disable();
ps.createSpring(a,b);
ps.createSpring(b,c);
ps.createSpring(c,d);
Particle* prev_particle = d;
int n = 15;
for(int i = 0; i < n; ++i) {
Particle* p = ps.createParticle(Vec3(-5+i*0.4, 7.5,0));
ps.createSpring(prev_particle, p);
p->setMass(0.5+(1.0-(float)i/n) * 4.0);
prev_particle = p;
}
wind = false;
invert = false;
paused = false;
}
//--------------------------------------------------------------
void testApp::update(){
static int counter = 0;
ofSetWindowTitle(ofToString(ofGetFrameRate()));
float t = ofGetElapsedTimeMillis() * noise_z;
donnie.noise(noise_x, noise_y, t, radius);
// apply some forces to the ParticleSystem (variable ps) so the springs move along.
if(!paused) {
++counter;
float x = 0.0f;
if(wind) {
x = sin(counter * 0.04) * 0.03;
}
float inv = (invert) ? -1 : 1;
ps.addForce(Vec3(x,-0.01 * inv,0));
ps.update();
}
}
//--------------------------------------------------------------
void testApp::draw(){
renderer.debugDraw();
ps.debugDraw();
// calculate orientation frames.
Vec3 V = ps.springs[0]->a->position - ps.springs[0]->b->position ; // these are the first points
Vec3 T(0,1,0);
Vec3 D(0,0,1);
Vec3 U(0,1,0);
Vec3 U_prev = U;
Vec3 D_prev = D;
Vec3 V_prev = V;
vector<Spring*>& springs = ps.springs;
int num = springs.size();
for(int i = 0; i < num-1; ++i) {
Spring* sa = springs[i];
Spring* sb = springs[i+1];
Particle* a = sa->a;
Particle* b = sa->b;
Particle* c = sb->b;
Vec3 t0 = (b->position - a->position).getNormalized();
Vec3 t1 = (c->position - b->position).getNormalized();
Vec3 B = cross(t0, t1);
if(B.length() <= 0.01) {
V = V_prev;
D = D_prev;
}
else {
B.normalize();
float theta = acos(dot(t0, t1));
V.rotate(theta, B);
D.rotate(theta, B);
U.rotate(theta, B);
}
float angle = acos(dot(t0, t1));
glBegin(GL_LINES);
// rotated up
glColor3f(0,1,0);
glVertex3fv(a->position.getPtr());
glVertex3fv((a->position + V).getPtr());
glColor3f(1,1,0);
glVertex3fv(a->position.getPtr());
glVertex3fv((a->position + D).getPtr());
glColor3f(0,1,1);
glVertex3fv(a->position.getPtr());
glVertex3fv((a->position + U).getPtr());
// corrected right
glColor3f(1,0,0);
glVertex3fv(a->position.getPtr());
glVertex3fv((a->position + B).getPtr());
glEnd();
// create circle around "U" axis.
int num_segments = 10;
Vec3 to_rotate = D;
float angle_to_rotate = TWO_PI/(float)num_segments;
V.normalize();
D.normalize();
glColor3f(1,1,1);
glBegin(GL_LINE_LOOP);
for(int i = 0; i < num_segments; ++i) {
to_rotate.rotate(angle_to_rotate, V);
glVertex3fv((a->position + to_rotate).getPtr());
}
glEnd();
V_prev = V;
D_prev = D;
}
}
@roxlu
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roxlu commented Dec 27, 2011

I can't spot something wrong with it. But also cannot believe it's so trivial :) please correct me if I'm wrong :)

@nardove
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nardove commented Mar 6, 2012

Vec3, Spring !? are these your custom classes? or are they part of the new OF 0071? Thanks for the code by the way I was just about to take a stab at it

@trentbrooks
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trentbrooks commented Mar 13, 2012

I've got the same question as nardove. And how have you defined the 3 properties/Particles (a,b,c) for a spring? Do you have the rest of the source code?

@roxlu
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roxlu commented Mar 13, 2012

Hi Trent and Nardove. The Vec3 is a typical vector3 class; you can use any, but if you're using openFrameworks that will be ofVec3f. The spring implements hooks law (http://en.wikipedia.org/wiki/Hooke's_law) It has two member "a" and "b" which are the particles. When a spring is create the distance between the particle (a and b) is used as the rest length.

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