We study in this paper the use of a 3D interface for OLAP. We analyze the state of the art in OLAP 3D visualizations. In a first step, we propose a new interface, called VR4OLAP, that combines the relative advantages of the studied methods. VR4OLAP can visualize 3 dimensions of an OLAP data cube and up to two measures. It represents the OLAP operators in the visualization with 3D widgets. It can use a 3D stereoscopic screen with a 3D mouse. In a second step, we perform a user study to evaluate this interface and to compare it with a standard cross-table. We evaluate the technical performances of the 3D interface. We conclude that, for the studied data and methods, 1) users are quite enthusiastic with a 3D representation, 2) the performances in 2D are equal or better than those obtained in 3D, 3) no advantage was found with the use of the 3D immersive setup.

In this paper, we propose a new method for the visual reorganization of online analytical processing (OLAP) cubes that aims at improving their visualization. Our method addresses dimensions with hierarchically organized members. It uses a genetic algorithm that reorganizes k-ary trees. Genetic operators perform permutations of subtrees to optimize a visual homogeneity function. We propose several ways to reorganize an OLAP cube depending on which set of members is selected for the reorganization: all of the members, only the displayed members, or the members at a given level (level by level approach). The results that are evaluated by using optimization criteria show that our algorithm has a reliable performance even when it is limited to 1 minute runs. Our algorithm was integrated in an interactive 3D interface for OLAP. A user study was conducted to evaluate our approach with users. The results highlight the usefulness of reorganization in two OLAP tasks.