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  Mapping mouse x,y to local world x,y equivalents  (Read 916 times)
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Offline jleone

Junior Newbie

« Posted 2006-02-10 16:59:47 »

I am capturing x,y mouseclicks on a Canvas3D and I want to see how they translate to x,y coordinates based on the coordinate system of  a specific shape in the scene.  I am able to convert the mouse coords to virtual world coords using a previously posted approach (pasted below), but I need the coords relative to the shape (which may be rotated,
translated, or zoomed in relation to the main virtual world). 

Is this clearly described?  Any ideas?

     * determines a corresponding virtual world point given a canvas point.
     * @param Point3d  the point on the canvas
     * @return Point3d  a virtual world point corresponding to thecanvas point
     *                  provided.
    public Point3d getCanvasPtToVworldPt(int x, int y) {
         // convert the canvas point to ImagePlate coords
        Point3d VworldPt = new Point3d();
        this.canvas.getPixelLocationInImagePlate(x, y, VworldPt);

        // transform the point from an imageplate coordinate to a
        // coordinate
        Transform3D imagePlateToVworld = new Transform3D();

        Point3d centerEyePt = new Point3d();

        //now compute the z=0 value  in the centereye to VworldPt pt
        //centerEyePt_VworldPt = alpha *centerEyePt_planePt with
        double alpha = 0.0;

        if ( VworldPt.z != centerEyePt.z ) {
            alpha = centerEyePt.z /(VworldPt.z - centerEyePt.z);

        Point3d planePt =  new Point3d(
                        centerEyePt.x- alpha *(VworldPt.x - centerEyePt.x),
                        centerEyePt.y - alpha *(VworldPt.y - centerEyePt.y),

      return planePt;
Offline Jeff

JGO Coder

Got any cats?

« Reply #1 - Posted 2006-02-11 01:55:18 »


If I am understanding you correctly I would getLocalToVWorld on the shape node and take the inverse.

But I dont knwo how you plan to map 2d coordinates into a 3D coordinate system.  Your missing one coord.

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