cpBody* drawing_update(cpSpace *space, cpBody *drawing, cpFloat x, cpFloat y) {
Body_data *pa = cpBodyGetUserData(drawing);
int length = pa->x_values->len;
cpVect old = cpvzero;
old.x = g_array_index(pa->x_values, cpFloat, length - 1);
old.y = g_array_index(pa->y_values, cpFloat, length - 1);
old = cpBodyLocal2World(drawing, old);
cpVect point = cpv(x, y);
// if the difference between the new x and the previous x is greater than the threshold
if (cpvdistsq(old, point) > THRESHOLD) {
cpVect position = cpBodyGetPos(drawing);
point = cpvsub(point, position);
//cpBodyWorld2Local(drawing, point);
fprintf(stdout, "Point= (%5.2f, %5.2f) while x= %5.2f, y=%5.2f\n", point.x, point.y, x, y);
x = point.x;
y = point.y;
g_array_append_val(pa->x_values, x);
g_array_append_val(pa->y_values, y);
cpBodySetUserData(drawing, pa);
drawing = add_segment_to_body(space, drawing);
}
cpBodySetVel(drawing, cpvzero);
return drawing;
}
// set gravity (of previously chosen objects) to point towards black holes
void orbit(cpBody * body, cpVect gravity, cpFloat damping, cpFloat dt)
{
extern struct objnode objroot[];
struct objnode *objx;
struct cpBody *hole;
cpVect bpos, hpos, unitv, gvect;
cpFloat hmass, g, distsq;
objx = objroot;
while ((objx = objx->next) != NULL) {
if (objx->bhole == true && objx->b != body) {
hole = objx->b;
bpos = cpBodyGetPos(body);
hpos = cpBodyGetPos(hole);
distsq = cpvdistsq(hpos, bpos);
distsq = (distsq == 0) ? 1e-50 : distsq; // don't divide by zero
hmass = cpBodyGetMass(hole);
g = hmass * BGRAV * (1 / distsq);
g = (distsq < RDSQ) ? g * -REPFS : g; // shoot close balls away
unitv = cpvmult(cpvsub(hpos, bpos), (1 / sqrt(distsq)));
gvect = cpvmult(unitv, g);
cpBodyUpdateVelocity(body, gvect, damping, dt);
}
}
}
cpFloat
cpMomentForSegment(cpFloat m, cpVect a, cpVect b, cpFloat radius)
{
// TODO account for radius
cpVect offset = cpvmult(cpvadd(a, b), 0.5f);
return m*(cpvdistsq(b, a)/12.0f + cpvlengthsq(offset));
}
cpFloat
cpMomentForSegment(cpFloat m, cpVect a, cpVect b)
{
cpVect offset = cpvmult(cpvadd(a, b), 0.5f);
return m*(cpvdistsq(b, a)/12.0f + cpvlengthsq(offset));
}
