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Transformation of 2D coordinates to 3D coordinates

September 19, 2017 - 3:35am #1


I have a problem with transformation of 2D coordinates to 3D coordinates.

Based on the "Obje reco" example I've added my own 3d marker (motorcycle model) and above it I show a simple texture (simple png with text). After that I wrote a simple handler on tap event:


public boolean onSingleTapUp(MotionEvent e) {
    if (mRenderer.isTapOnScreenInsideTarget(e.getX(), e.getY())){
    } else {
        autofocusHandler.postDelayed(new Runnable() {
            public void run() {
                boolean result = CameraDevice.getInstance().setFocusMode(CameraDevice.FOCUS_MODE.FOCUS_MODE_TRIGGERAUTO);
                if (!result)
                    Log.e("SingleTapUp", "Unable to trigger focus");

        }, 1000L);
    return true;


In the ObjectTargetRenderer I have a method isTapOnScreenInsideTarget (I've found a java implementation of that method on some post of this forum):


public boolean isTapOnScreenInsideTarget(float x, float y) {
    Vec3F intersection;

    if (isTracked) {
        DisplayMetrics metrics = new DisplayMetrics();

        intersection = SampleMath.getPointToPlaneIntersection(
            modelViewMatrix_Vuforia, metrics.widthPixels, metrics.heightPixels,
            new Vec2F(x, y), new Vec3F(0, 0, 0), new Vec3F(0, 0, 1));

        float leftX = targetPositiveDimensions.getData()[0] - 0.5f * targetPositiveDimensions.getData()[0];

        float rightX = targetPositiveDimensions.getData()[0] + 0.5f * targetPositiveDimensions.getData()[0];

        float bottomY = targetPositiveDimensions.getData()[1] - 0.5f * targetPositiveDimensions.getData()[1];

        float topY = targetPositiveDimensions.getData()[1] + 0.5f * targetPositiveDimensions.getData()[1];

        if ((intersection.getData()[0] >= leftX) && (intersection.getData()[0] <= rightX)
            && (intersection.getData()[1] >= bottomY) && (intersection.getData()[1] <= topY)) {

            return true;
    return false;


Simple texture above the motorcycle model is in the position:


new double[]{ -0.50f, -0.50f, 1.50f, 0.50f, -0.50f, 1.50f, 0.50f, 0.50f, 1.50f, -0.50f, 0.50f, 1.50f}


I have a 3d marker so to have a texture above the 3d marker I've changed z axis.

The problem is in transforming the tap coordinates to the texture coordinates. In targetPositiveDimensions I have always coordinates of the beginning of my marker not my texture above it. Maybe I forgot about some transformation? Could you give me some advice?

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