No, I didnt find any problem like that. Guess Im luckyer!
On Tue, Sep 2, 2008 at 10:18 PM, Ari Braginsky <[EMAIL PROTECTED]> wrote:
>
> Li,
>
> Thank you for your post. I'm not sure if your solution is the same as
> the solution that I need for my problem.
>
> To clarify, I'm moving a point around on a mesh that has a bitmap
> image inside of it. When I move that point, I need to track the
> relative position of that point on the bitmap in normal 2D space in
> order to measure the pixel color value at that point.
>
> Because of the subdivision values, the bitmap image inside of the mesh
> is deformed such that when your point is on top of a feature in the
> bitmap mesh, it doesn't exactly line up with the same converted (by
> way of the mesh X and Y scale division method) point on the 2D
> bitmap. It is somewhat off.
>
> I need to be able to adjust for the subdivision distortion.
>
> Is this similar to your problem that was solved with your solution?
>
> Thanks,
> Ari
>
>
> On Sep 2, 8:06 pm, Li <[EMAIL PROTECTED]> wrote:
> > Hey Ari,
> >
> > Ive been working with a similar issue in reflections. The solution I used
> > might be useful to you. The particular problem I had was, once I obtained
> a
> > 3d point that I knew was on the surface of a plane, what would be the 2d
> > coordinates of that point on the plane? The solution involved determining
> > the top side and left side vectors of the plane, obtaining a vector from
> the
> > top left corner of the plane to the 3d point, and then using dot products
> to
> > project that vector onto the side vector. That gives you a scalar value
> that
> > corresponds to the coordinate system transformation of the point.
> >
> > If you think it might help you, here is the code:
> >
> > //Three vertices.
> > edgePoint = getVertexGlobalPosition(plane.vertices[0],
> > plane);
> > var p2:Number3D =
> getVertexGlobalPosition(plane.vertices[1],
> > plane);
> > var p3:Number3D =
> getVertexGlobalPosition(plane.vertices[4],
> > plane);
> >
> > //Side vectors.
> > topVector = new Number3D();
> > topVector.sub(p2, edgePoint);
> > sideVector = new Number3D();
> > sideVector.sub(p3, edgePoint);
> >
> > wRatio = MovieMaterial(plane.material).movie.width/plane.width;
> > hRatio =
> > MovieMaterial(plane.material).movie.height/plane.height;
> >
> > //TRANSLATE GLOBAL TO PLANE.
> > //Translates a world 3D point to a corresponding 2D point
> on
> > the plane's material.
> > private function
> > translateGlobalToPlane(point:Number3D):Point
> > {
> > /*
> > Finds a vector from one of the corners of the
> plane
> > to the point,
> > and projects this vector on its sides,
> considering
> > scaling.
> > */
> > var v:Number3D = new Number3D();
> > v.sub(point, edgePoint);
> > return new
> > Point(wRatio*v.dot(topVector)/topVector.modulo, hRatio*(this.height -
> > v.dot(sideVector)/sideVector.modulo));
> > }
> >
> > //GET VERTEX GLOBAL POSITION.
> > //Translates vertex coordinates to world coordinates.
> > private function getVertexGlobalPosition(vertex:Vertex,
> > vertexContainer:Object3D):Number3D
> > {
> > var m:Matrix3D = new Matrix3D();
> > m.tx = vertex.x;
> > m.ty = vertex.y;
> > m.tz = vertex.z;
> > m.multiply(vertexContainer.transform, m);
> > return new Number3D(m.tx, m.ty, m.tz);
> > }
> >
> > On Tue, Sep 2, 2008 at 9:34 PM, Ari Braginsky <[EMAIL PROTECTED]>
> wrote:
> >
> > > I'm having an issue retrieving 2D coordinates off of a mesh based on a
> > > 3D object's position on the mesh.
> >
> > > You can normally retrieve the 2D coordinates on the bitmap making up
> > > the mesh by dividing the coordinates of the object by the mesh's X and
> > > Y scale values (see extrusions/CollisionMap.as class).
> >
> > > However, if you look at the position on the mesh and compare it to the
> > > raw bitmap, due to some deformations that happen to the mesh with
> > > certain subdivision values, the objects that appear in the bitmap
> > > don't line up with the 2D coordinates on the raw bitmap. If you tweak
> > > the subdivision values, the objects on the bitmap in the mesh move
> > > around/get squashed/etc.
> >
> > > Example:
> >
> > > Create a bitmap with a circle in the center filled with the color red.
> >
> > > Create an elevation using a flat height map and use the bitmap for its
> > > skin.
> >
> > > When rendered in 3D, you will see the red circle in the center of the
> > > mesh. If you move your mouse over it, you can translate the 3D
> > > coordinates into 2D space and divide them by the mesh's X and Y scale
> > > values to get the real coordinates on the raw bitmap.
> >
> > > What I'm seeing with subdivision values X = 200 and y = 200 is that my
> > > point on the mesh doesn't correlate to the same point on the 2D bitmap
> > > when I convert the 3D coordinates to 2D, taking into account the mesh
> > > scale values.
> >
> > > Is there something else I need to do to account for the subdivision
> > > values?
> >
> > > If I didn't want any deformation of the mesh, are there subdivision
> > > values I can use such that 3D points on the mesh would exactly match
> > > up with 2D points on the associated bitmap?
> >
> > > Thanks,
> > > Ari
>
