velo works with a tree of Node objects, each of which has a position and a rotation relative to its parent Node. This concept is called scene graph.
Whenever the user changes a Node object's parent, position or rotation, the internal function _u() recomputes the absolute position _aP and absolute rotation _aR. The Node can then draw itself easily, using _aP and _aR.
This way, rendering will be fast, because nested transformations don't have to be recomputed on each render cycle.
velo sacrifices automatic scene graph management in favor of a smaller footprint. You have to manage the scene graph manually. If you don't keep the scene graph consistent, kittens will die! An inconsistent scene graph may lead to invisible or offset nodes. Also, take care that a node never is a child of two nodes.
To give you an example, let's say you have two nodes node1 and node2. When you add node2 to node1's list of children, don't forget to set node2's parent to node1, either on setup (method a) or later (method b).
velo.array.add(node1.children, node2);
// Method `a` – specify the parent on setup
node2 = velo.n({
…
parent: node1
…
});
// Method `b` – specify the parent later
node2.parent(node1);When you remove node2 from node1's list of children, don't forget to set node2's parent to null.
velo.array.remove(node1.children, node2);
node2.parent(null); // This is important!todo