Abstract: The present invention relates to a method and system for processing a volumetric dataset for providing close-up visualization of a subset therefrom. A volumetric dataset is processed based on a dual access gradient quantization data structure. The data structure is generated in a fast pre-processing stage and provides substantially immediate access to a quantized gradient using either an index or an arbitrary normalized vector. The method provides a clear, enlarged high-resolution image of a user selected region of interest at interactive rates and allows the user to freely move and visualize the region of interest within the volumetric dataset and with any orientation.