[]webGL模式下 graphic画线涂鸦，一直不停画会出现线条异常

pos0:Laya.Point=new Laya.Point();

    pos1:Laya.Point=new Laya.Point();

    __mouseDown(e:Event){

        this.pos0.x=this.bmp.mouseX;

        this.pos0.y=this.bmp.mouseY;

        this.pos1.x=this.bmp.mouseX

        this.pos1.y=this.bmp.mouseY;

        this.bmp.on(Laya.Event.MOUSE_MOVE, this, this.__mouseMove);

        this.bmp.on(Laya.Event.MOUSE_UP, this, this.__mouseUp);

        console.log(this.pos0.x);

    }

    __mouseMove(e:Event){

        this.pos1.x=this.bmp.mouseX

        this.pos1.y=this.bmp.mouseY;

        if(Utils3D.getThis.getDistance(this.pos0,this.pos1)>10){

            this.bmp.graphics.drawLine(this.pos0.x,this.pos0.y,this.pos1.x,this.pos1.y,"#ff0000",5);

            this.pos0.x=this.bmp.mouseX;

            this.pos0.y=this.bmp.mouseY;

        }

    }

    __mouseUp(e:Event){

        this.bmp.off(Laya.Event.MOUSE_MOVE, this, this.__mouseMove);

        this.bmp.off(Laya.Event.MOUSE_UP, this, this.__mouseUp);

        this.bmp.graphics.drawLine(this.pos0.x,this.pos0.y,this.pos1.x,this.pos1.y,"#ff0000",5);

    }