Calculate coordinate system based on direction vector

coordinate_system.cpp

void Tubes::computeEdgeCoordinateSystems() {
	Vec3 dir;
	float inv = 0.0f;
	vector<Edge*>::iterator it = graph.edges.begin();
	while(it != graph.edges.end()) {
		Edge* e = (*it);
		dir = graph.getEdgeDirection(e).normalize();
		e->z_axis = dir;
		if(fabsf(dir.x) > fabsf(dir.y)) {
			inv = 1.0f / sqrtf(dir.x*dir.x + dir.z*dir.z);
			e->y_axis.set(-dir.z * inv, 0.0f, dir.x * inv);
		}
		else {
			inv = 1.0f / sqrtf(dir.y*dir.y + dir.z*dir.z);
			e->y_axis.set(0.0f, dir.z * inv, -dir.y * inv);
		}
		e->x_axis = cross(e->z_axis, e->y_axis);
		++it;
	}	
}