for (let c = r + 1; c < this._width; c++) {
                let k = (r*this._width + c)*2;
                let v1 = this._buffer[k];
                let v2 = this._buffer[k+1];
                if (isNaN(v1) || isNaN(v2) || v1*v1 + v2*v2 > epsilon*epsilon) {