# Posts tagged ‘notes’

1. In 3d the product of matrix multiplication is always in world space.

2. An objects transform is a product of its target space multiplied by its reference space.

This second part is really vital to understand, (I dont think I’ve phased it myself well enough here even) But basically it means that if your transforming an object by the world, but the object is parented the difference between the object and its target space need to be multiplied by the objects local space.

I’ll try to describe this more with pics.

Just wanted to give a quick run down of how my brain works tackling a problem, I recently saw a video of a dynamic tail a friend of mine had sent me – the obvious approach would be verlet, a system where you can keep overlaying solvers ontop of solvers. But another key system the tail had was to maintain its shape whilst being dynamic this sent my brain into overide! How is this possible – here’s how my brain would solve it (this hasn’t been tested, all theoretical):

A chain of controls, points and bones. Get the transform space of the second control onwards, build a verlet framework of the points, with stiff rods connecting them and point constraints made by getting the relative space of the control relative to its parent multiplied by the same points direction , i.e point 3 use the transform position of control 3 relative control 2 multiplied by the direction of point 2 – point 1. Finally build a matrix transform from this and apply it to the skeletal chain consecutively.

Now i dont know if this is correct, but this is how my mind thinks – i build little systems and stick them together, then i spend the biggest chunk of time getting the systems to talk nicely to each other.