void readData(boolean isMapData) {
		isJvxl = false;
		endOfData = false;
		mappedDataMin = Float.MAX_VALUE;
		int nSurfaces = readVolumetricHeader();
		if (nSurfaces < fileIndex) {
			Logger.warn("not enough surfaces in file -- resetting fileIndex to " + nSurfaces);
			fileIndex = nSurfaces;
		}
		if (isJvxl && isMapData)
			try {
				int nPoints = nPointsX * nPointsY * nPointsZ;
				gotoData(fileIndex - 1, nPoints);
				jvxlSkipData(nPoints, false);
			}
			catch (Exception e) {
				Logger.error(null, e);
			}
		else readVolumetricData(isMapData);
	}