You can have a look at my blog post:
http://alokgandhi.com/blog/2012/05/28/barycentric-coordinates-and-the-magic-of-locations/
On Wed, Jul 17, 2013 at 12:58 PM, Ben Houston <b...@exocortex.com> wrote:
> BTW here is our code for calculating barycoordinates from points and
> creating points from barycoordinates:
>
> template<class T>
> class Triangle3 {
> public:
> Vec3<T> a;
> Vec3<T> b;
> Vec3<T> c;
>
> Matrix44<T> getPointToBarycoordMatrix() const;
> Matrix44<T> getBarycoordToPointMatrix() const;
> };
>
> template<class T>
> inline Matrix44<T> Triangle3<T>::getPointToBarycoordMatrix() const {
> M44x pointToBarycoordMatrix;
> bool success = inverseSafe( pointToBarycoordMatrix,
> getBarycoordToPointMatrix() );
> if( ! success ) {
> T oneThird = ((T)1.0)/((T)3.0);
> //Vec3<T> center = ( a + b + c ) * oneThird;
> return Matrix44<T>(
> 0, 0, 0, 0,
> 0, 0, 0, 0,
> 0, 0, 0, 0,
> oneThird, oneThird, oneThird, 0);
> }
> return pointToBarycoordMatrix;
> }
>
> template<class T>
> inline Matrix44<T> Triangle3<T>::getBarycoordToPointMatrix() const {
> Vec3<T> n = normal();
> return Matrix44<T>(
> a[0], a[1], a[2], 1,
> b[0], b[1], b[2], 1,
> c[0], c[1], c[2], 1,
> n[0], n[1], n[2], 0);
> }
>
> And this you just multiple your point by the "pointToBarycoordMatrix"
> matrix to get barycoords. And if you have barycoordinates, multiply
> it by "getBarycoordToPointMatrix()" to get your point.
>
> We are using 4 coordinate barycoordinates where the fourth element is
> the distance from the triangle plane in the normal direction. Just
> set it to zero and you should be fine. The above can be converted to
> Softimage Matrix types pretty easily. Probably could be added to the
> Softimage SDK as well if it isn't already there.
>
> Best regards,
> -ben
>
>
> On Wed, Jul 17, 2013 at 12:04 PM, Ben Houston <b...@exocortex.com> wrote:
> > So barycoords for a triangle works well and I believe there are tons
> > of references on the web for this. Barycoordinates for polygons is a
> > bit more problematic because they are no longer linear but rather
> > polynomials and thus harder to calculate. I'd stick with triangles
> > and then all those web references should work well.
> >
> > Is your problem calculating them from points?
> >
> > Basically this is a great guide:
> >
> > http://en.wikipedia.org/wiki/Barycentric_coordinate_system
> >
> > -ben
> >
> >
> > On Wed, Jul 17, 2013 at 11:38 AM, <p...@bustykelp.com> wrote:
> >> Hi, I have spent days on this and I cant work it out
> >>
> >> I have a selection of points (not on a flat plane) and I have a test
> >> position.
> >> It returns an array that represents the weighting, related to the
> proximity
> >> to the other points.
> >>
> >> I want to have it so that when the test position is directly at a
> point, the
> >> value for that point in the array = 1
> >> and the rest will be zero
> >> as the test point moves around the area it interpolates these values,
> but
> >> they always add up to 1
> >>
> >> It sounds really easy, but I’ve been literally* tearing my hair out over
> >> this for days.
> >>
> >> Ive managed to get barycentric interpolation working for a flat plane,
> and
> >> only 3 points, but I need it to accept multiple points in 3d space.
> >>
> >> Please help. I’m going bonkers over this
> >>
> >> Paul
> >>
> >> *(not really literally)
> >
> >
> >
> > --
> > Best regards,
> > Ben Houston
> > Voice: 613-762-4113 Skype: ben.exocortex Twitter: @exocortexcom
> > http://Exocortex.com - Passionate CG Software Professionals.
>
>
>
> --
> Best regards,
> Ben Houston
> Voice: 613-762-4113 Skype: ben.exocortex Twitter: @exocortexcom
> http://Exocortex.com - Passionate CG Software Professionals.
>
>
--
