值
                    projMatrix : matrix.projMatrix,
                    returnPoint : true
                }
            );
            const { meshId, pickingId, point } = picked;
            return point;
        }

        function handleMouseDown(ev) {
            if (scanning) {
                mouseDown = true;
                lastMouseX = ev.clientX;
                lastMouseY = ev.clientY;
            } else if (drawing) {
                const drawPoint = getPickingPoint(ev.clientX, ev.clientY)