PerspectiveOffCenterLens

/*
Usage:
_lens = new PerspectiveOffCenterLens(45);
_lens.left = 0.3;  // move projection center to 0.3 * width of viewPort
_lens.top = 0.5; // center of y-axis (0.5 * with of viewPort)
_view = new View3D(null, new Camera3D(_lens))
*/
package ait.components.object3d.camera.lens
{
    import away3d.cameras.lenses.LensBase;
    import away3d.core.math.Matrix3DUtils;

    import flash.geom.Vector3D;

    public class PerspectiveOffCenterLens extends LensBase
    {
        private var _fieldOfView : Number;
        private var _focalLengthInv : Number;
        private var _yMax : Number;
        private var _xMax : Number;
        private var _left:Number;
        private var _top:Number;


        public function PerspectiveOffCenterLens(fieldOfView : Number = 60, left:Number = 0.5, top:Number = 0.5)
        {
            this.fieldOfView = fieldOfView;
            this.left = left;
            this.top = top;
        }

        public override function project(point3d : Vector3D) : Vector3D
        {
            //In dev version of Away3D 4.1.0 - LensBase.as
            //TODO this function was affected by commit 21a6cea0fa644d812c418aca665e31ab5fb1f73e, applied reverting override

            var v : Vector3D = matrix.transformVector(point3d);
                v.x = v.x/v.w;
                v.y = -v.y/v.w;

                //z is unaffected by transform
                //v.z = point3d.z;

            return v;
        }

        /**
         * Calculates the position of the given normalized coordinates relative to the camera.
         * @param mX The x coordinate relative to the View3D. -1 corresponds to the utter left side of the viewport, 1 to the right.
         * @param mY The y coordinate relative to the View3D. -1 corresponds to the top side of the viewport, 1 to the bottom.
         * @param mZ The distance from the projection plane.
         * @return The scene position of the given screen coordinates.
         */
        public override function unproject(mX:Number, mY:Number, mZ : Number):Vector3D
        {
            //In dev version of Away3D 4.1.0 - LensBase.as
            //TODO this function was affected by commit 21a6cea0fa644d812c418aca665e31ab5fb1f73e, applied reverting override

            var v : Vector3D = new Vector3D(mX, -mY, mZ, 1.0);

            v = unprojectionMatrix.transformVector(v);

            var inv : Number = 1/v.w;

            v.x *= inv;
            v.y *= inv;
            v.z *= inv;
            v.w = 1.0;

            return v;
        }


        public function get fieldOfView() : Number { return _fieldOfView; }
        public function get left():Number { return _left };
        public function get top():Number { return _top };

        public function set fieldOfView(value : Number) : void
        {
            if (value == _fieldOfView) return;
            _fieldOfView = value;

            _focalLengthInv = Math.tan(_fieldOfView*Math.PI/360);
            invalidateMatrix();
        }

        /**
         *
         * @param value
         *
         */
        public function set left(value:Number):void
        {
            _left = value;
            invalidateMatrix();
        }

        /**
         *
         * @param value
         *
         */
        public function set top(value:Number):void
        {
            _top = value;
            invalidateMatrix();
        }

        /**
         *
         *
         */
        override protected function updateMatrix() : void
        {
            var yScale:Number = (1.0/Math.tan( (fieldOfView*Math.PI/360)));
            var xScale:Number = (yScale / _aspectRatio);

            var xScaleTotal:Number = 2 * _near / xScale;
            var left:Number = - _left * xScaleTotal;
            var right:Number = (1 - _left) * xScaleTotal;

            var yScaleTotal:Number = 2 * _near / yScale;
            var bottom:Number = (_top - 1) * yScaleTotal;
            var top:Number = _top * yScaleTotal;


            var raw : Vector.<Number> = Matrix3DUtils.RAW_DATA_CONTAINER;

            // assume symmetric frustum
            raw[uint(0)] = 2.0*_near/(right-left);
            raw[uint(5)] = -2.0*_near/(bottom-top);
            raw[uint(8)] = -1.0-2.0*left/(right-left);
            raw[uint(9)] = 1.0+2.0*top/(bottom-top);
            raw[uint(5)] = -2.0*_near/(bottom-top);
            raw[uint(10)] = -_far/(_near-_far);
            raw[uint(11)] = 1;
            raw[uint(1)] = raw[uint(2)] = raw[uint(3)] = raw[uint(4)] =
                raw[uint(6)] = raw[uint(7)] =
                raw[uint(12)] = raw[uint(13)] = raw[uint(15)] = 0;
            raw[uint(14)] = (_near*_far)/(_near-_far);

            _matrix.copyRawDataFrom(raw);

            _yMax = _near * _focalLengthInv;
            _xMax = _yMax * _aspectRatio;

            var yMaxFar:Number = _far * _focalLengthInv;
            var xMaxFar:Number = yMaxFar * _aspectRatio;

            _frustumCorners[0] = _frustumCorners[9] = -_xMax * _left;
            _frustumCorners[3] = _frustumCorners[6] = _xMax * (1 - _left);
            _frustumCorners[1] = _frustumCorners[4] = -_yMax * _top;
            _frustumCorners[7] = _frustumCorners[10] = _yMax * (1 - _top);

            _frustumCorners[12] = _frustumCorners[21] = -xMaxFar * _left;
            _frustumCorners[15] = _frustumCorners[18] = xMaxFar * (1 - _left);
            _frustumCorners[13] = _frustumCorners[16] = -yMaxFar * _top;
            _frustumCorners[19] = _frustumCorners[22] = yMaxFar * (1 - _top);

            _frustumCorners[2] = _frustumCorners[5] = _frustumCorners[8] = _frustumCorners[11] = _near;
            _frustumCorners[14] = _frustumCorners[17] = _frustumCorners[20] = _frustumCorners[23] = _far;

            _matrixInvalid = false;
        }
    }
}