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

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