The idea is to create quad_strip ribbon my filling up a matrix, with
the width of the ribbon being calculated using the crossproduct using
previous positions :

vector 1 being :
current position - previous position

vector 2 :
previous position - the position before that

and then calculating the crossproduct of those 2 vectors, normalizing
it, and then some stuff with adding the current position to the
crossproduct and using that value for the even vertices of the
quad_strip. (I think it sounds clearer in my head, but it is for
doing something like this :

http://www.youtube.com/watch?v=fM1qj_OFY4w )

On 27 Sep 2007, at 12:56, Ranja Achbar wrote:

> Hi Brecht,
>
> I'm not sure but maybe a shader can help. Parts of the shaders
> derivatives are don with matrix calculations.
> It's only an idea. Maybe a bit more complicated. But matrices
> calculations are much faster on gpu than on cpu.
>
> grr.
> Ranja
>
> 2007/9/27, Brecht Debackere :
> Just a quick question to all the mathbuffs out there...
>
> I want to get the crossproduct of 2 vectors, and for this I set up
> 2 matrices going into jit.expr with the following expression :
>
> expr "(in[1].p[2]*in[2].p[3])-(in[1].p[3]*in[2].p[2])" "(in[1].p[3]
> *in[2].p[1])-(in[1].p[1]-in[2].p[3])" "(in[1].p[1]*in[2].p[2])-(in
> [1].p[2]*in[1].p[3])"
>
> I was wondering if this is correct, and maybe if there's a much
> more simple expression or object for this...?
>
> grtz.
>
> Brecht Debackere
>
> www.autofasurer.net
> M+32(0)498319302
> F+32(0)70429559
> Skype : Bdebackere
> brecht@visualantics.net
>
>
>
>
>
>

Brecht Debackere

www.autofasurer.net
M+32(0)498319302
F+32(0)70429559
Skype : Bdebackere
brecht@visualantics.net