I am trying to create a 2D Stage3D game where you can move the camera around the level in an RTS style. I thought about using Orthographic Matrix3D functions for this but when I try to scroll the whole "stage" also scrolls.

This is the Camera code:

    public function Camera2D(width:int, height:int, zoom:Number = 1) {
        resize(width, height);
                    _zoom = zoom;
    }

    public function resize(width:Number, height:Number):void {
        _width = width;
        _height = height;

        _projectionMatrix = makeMatrix(0, width, 0, height);

        _recalculate = true;
    }

    protected function makeMatrix(left:Number, right:Number, top:Number, bottom:Number, zNear:Number = 0, zFar:Number = 1):Matrix3D {
        return new Matrix3D(Vector.<Number>([
            2 / (right - left), 0, 0, 0,
            0, 2 / (top - bottom), 0, 0,
            0, 0, 1 / (zFar - zNear), 0,
            0, 0, zNear / (zNear - zFar), 1
        ]));
    }

    public function get viewMatrix():Matrix3D {
        if (_recalculate) {
            _recalculate = false;

            _viewMatrix.identity();
            _viewMatrix.appendTranslation( -_width / 2 - _x, -_height / 2 - y, 0);
            _viewMatrix.appendScale(_zoom, _zoom, 1);

            _renderMatrix.identity();
            _renderMatrix.append(_viewMatrix);

            _renderMatrix.append(_projectionMatrix);
        }

        return _renderMatrix;
    }

Here are two screenshots to show what I mean:

How do I only let the inside of the stage3D scroll and not the whole stage?