th.round(index);
                if (i > idx) {
                    this._params.idx++;
                    let ps = positions[i];
                    if (!ps) {
                        const result = chunkLines.slice(i, i + trail);
                        ps = getChunkLinesPosition(result, layer, positionMap, centerPt).positions;
                        this._params.positions[i] = ps;
                    }
                    setLineGeometryAttribute(this.getObject3d().geometry, ps);
                    th