Hello,

I’m trying to use skinning with collada and OSG. That’s my first skinning

experience.

The formula is given p 4-8 as:

```
outv = \Sum_i { ((v * BSM) * IBMi * JMi) * JW }
```

However v is in R^3 and BSM in R^{4x4} so the matrix product is not valid.

Am I missing something? What is the full formula?

I would have expected v to be replaced by [v(0) v(1) v(2) 1] but from my

tests with OSG, it seems more like [v(0) v(1) v(2) 0]. As a consequence

one cannot move the vertices located at [0 0 0].

Am I right? Is there a reason for this choice?

I’m trying to display forces (vectors in R^3) as animated arrows. My plan

is to attach a node to the tip of the arrow, and to translate it according

to the vector value.

In order to do this, I need to discard the orientation of the node, thus the

need for [0,0,0]-located vertices.

Here is a working (in OSG) example, illustrating this idea. The arrow is

a simple 2-vertices line.

http://gist.github.com/610049#file_skin_transl.dae

Here is a non-working one, where the vertex at [0,0,0] does not move.

http://gist.github.com/610049#file_skin … orking.dae

Maybe it would be simpler to scale and rotate the arrow. How would you do that?

Using matrix and scale? Or lookat and scale? Or rotate and scale (what happens

when the rotation axis is [0 0 0])?

Thank you for any insight.