A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy In The Department of Computer Science By Gaurav Khanduja B.E., Madan Mohan Malaviya Engg College, 2002 M.S., Louisiana State University, 2005 May 2009 MULTIPLE DATASET VISUALIZATION (MDV) FRAMEWORK FOR SCALAR VOLUME DATA ii To My Parents, Family And My beloved wife, Swati iii ACKNOWLEDGMENTS Foremost of all, I would like to thank my major advisor Dr. Bijaya B. Karki for guiding me through various stages of uncertainties and doubts. When I did not know what I was doing, he was the one who supported me, believed in me and guided me. I would also like to thank Dr. S. Sitharama Iyengar, Dr. Jianhua Chen and Dr. Brygg Ullmer for agreeing to be in my dissertation committee and providing valuable feedback. I would like to thank Dr. Charles Delzell, the dean’s representative, for his interest and constantly asking questions about the status of the work. I would like to acknowledge Dr. Ashok Verma and Dipesh Bhattarai for providing a stimulating intellectual environment in our laboratory and acting as a sounding board when I was not sure about the worth of my own thoughts. I would also like to express my thanks to Ms. Vera Watkins and Ms. Amy Fowler for taking care of the administrative details so that I could focus on my work. I would also like to express my gratitude to the whole Department of Computer Science for providing such an excellent environment for intellectual pursuit. I would also like to acknowledge the support from National Science Foundation and NASA for this research. I would not be here with this work if it were not for my family. Their excitement was always source of my energy that kept on motivating me through these four and half years. Last but not the least; I would like to express my sincere gratitude to my parents and my beloved wife, Swati, for pushing me hard so that I could finish this dissertation. They would not settle for less than the finished work. If it was not for them, I would not have been able to finish. This work belongs to them as much as it does to me. iv TABLE OF CONTENTS ACKNOWLEDGMENTS iii LIST OF TABLES …………………………………………………….…………………………………………………….vii LIST OF FIGURES viii ABSTRACT……………………………………………………………… ………………………………………………….xiv 1. INTRODUCTION 1 1.1 What Is Visualization? 1 1.2 Multiple Dataset Visualization 2 1.3 MDV Techniques 3 1.4 Challenges In MDV 5 1.4.1 Memory Requirement 5 1.4.2 Visualization Display 7 1.4.3 Performance and Interactivity 7 1.5 Areas of Application 8 1.6 Thesis Organization 10 2. RELATED WORK 11 2.1 Multiple Datasets 11 2.2 Computer Graphics 12 2.2.1 Coordinate System in 3D Computer Graphics 12 2.2.2 3D Graphics Rendering Pipeline 14 2.3 Overview of Visualization Techniques 15 2.3.1 Ray Casting 16 2.3.2 Splatting 17 2.3.3 Shear-Warp 17 2.3.4 2D and 3D Textures 18 2.3.5 Isosurface Extraction 18 2.4 Isosurface Rendering Technique 18 2.4.1 Introduction 18 2.4.2 Marching Cubes Algorithm 19 2.4.3 Dividing Cubes Algorithm 22 2.4.4 Span Space Based Approach 24 2.4.5 Isosurface Extraction Using Ray Tracing 25 2.5 Texture Mapping Technique 26 2.5.1 2D And 3D Textures 27 v 2.5.2 3D Texture Based Volume Rendering 28 2.5.3 Clipping 30 3. MDV FRAMEWORK 34 3.1 What Is Framework? 34 3.2 MDV Framework 35 3.2.1 Architecture 35 3.2.2 Multithreaded View 37 3.3 Data Loading Module 39 3.4 Visualization Module 40 3.5 Rendering Module 42 3.5.1 Rendering Time 43 3.6 Results 45 3.7 Implementation 47 4. ISOSURFACE EXTRACTION FOR MDV 49 4.1 MDV Framework and Isosurface Technique 49 4.2 Data Structure 49 4.3 Rendering Primitives 52 4.4 Visualization Techniques 53 4.4.1 All-In-Memory (AIM) Method 54 4.4.2 Only-Polygons-in-Memory (OPIM) Method 55 4.4.3 Performance Analysis 57 4.4.4 Performance Analysis (Points vs. Polygons) 60 4.5 Improving Isosurface Extraction for MDV 63 4.5.1 Data Coherency 63 4.5.2 Multi-Resolution 73 4.5.3 Quasi-4D Isosurface Extraction 84 5. TEXTURE-BASED RENDERING FOR MDV 88 5.1 Introduction 88 5.2 Texture Mapping 91 5.3 Transfer Function 91 5.4 Volume Rendering 92 5.5 External 3D Surface Rendering 94 5.6 Clipping 96 5.6.1 Clipping with External Surface Rendering 96 5.6.2 Volume Clipping 99 5.7 Hardware Isosurface Extraction 101 5.8 Hardware Based Isosurface Difference 102 5.9 DR Based Texture Mapping 103 5.10 Volume Shading 105 5.11 Performance Analysis 108 vi 6. APPLICATIONS: VISUALIZATION OF ELECTRON DENSITY DATA 112 6.1 Simulation Data 113 6.2 Simulation Data Visualization 114 6.2.1 MgO Data 114 6.2.2 MgSiO 3 Data 119 7. CONCLUSIONS AND FUTURE DIRECTIONS 124 7.1 Conclusions 124 7.2 Future Directions 126 REFERENCES…………………………………………………………………………………………………………… 128 APPENDIX A. PSEUDO CODE 136 A. 1. MDV Framework 137 A. 2. AIM Method 137 A. 3. OPIM Method 138 A. 4. Rendering Module 139 A. 5. Data Coherency 140 A. 6. Quasi-4D Isosurface Extraction 141 A. 7. Multi-Resolution 142 A. 8. Clipping 143 A. 9. Hardware Isosurface Extraction 144 APPENDIX B. PARALLEL IMPLEMENTATION OF THE FRAMEWORK 145 VITA………………………………. 148 vii LIST OF TABLES Table 1: Number of triangles with overlapping 69 Table 2: Description of terms in lighting equation 106 viii LIST OF FIGURES Figure 1: Ways for multiple dataset visualization 4 Figure 2: Two cubic volumes with spherical isosurface 6 Figure 3: MDV of 25 sets of electronic charged density using 3D surface texture mapping with planar clipping. The color and opacity values for each pixel are based on the density value associated with that pixel. A multiscale RGB color mapping is used. B represents values from 0 to 0.05, G is added to represent values up to 0.4 and then R is increased and both B and G are decreased for higher values. 9 Figure 4: Graphics Rendering Pipeline 14 Figure 5: Marching Cube cell 20 Figure 6: Different cases for intersection of surface with cube [4] 22 Figure 7: Span space for NIOSE algorithm 24 Figure 8: Division of span space for ISSUE algorithm 25 Figure 9: Relationship of 2D and 3D Textures 27 Figure 10: Basic steps in the visualization process 34 Figure 11: Multiple Dataset Visualization 36 Figure 12: Multithreaded Architecture 37 Figure 13: MDV Framework 38 ix Figure 14: Isosurface difference using GPU. Arrows show the difference in the isosurface in the box. First difference is based on data and second difference is based on depth using GPU. 41 Figure 15: Texture based difference for the magnesium silicate datasets. 43 Figure 16: Responsiveness and Latency for single and multi thread scenario 46 Figure 17: Single thread vs. Multi thread - Responsiveness (for marching cube and rendering time) 46 Figure 18: MDV Framework for isosurface extraction 49 Figure 19:Quadtree for calculating isosurfaces [71] 50 Figure 20: Octree for isosurface construction [72] 51 Figure 21: AIM Scheme 54 Figure 22: OPIM Scheme 56 Figure 23: Isosurface for isovalue = 0.02, 0.04, and 0.08 (left to right)[16] 57 Figure 24: AIM polygon generation (T G ) and rendering (T R ) times for isovalue = 0.02, 0.04 and 0.08 [16] 58 Figure 25: OPIM polygon generation (T G ) and rendering (T R ) times for isovalue = 0.02, 0.04, 0.08 [16] 59 Figure 26: AIM scheme 61 Figure 27: OPIM scheme 62 Figure 28: Visualization of electronic charge density using the data coherency technique. (a) Perfect crystal (reference data); (b) and (c) Non-reference data. Light region from reference dataset; dark region is directly extracted. 65 x Figure 29: Overlapping for eliminating crack in the dataset. (a) Reference isosurface; (b) Non-reference isosurface; (c) Approximated isosurface with cracks; (d) Approximated isosurface without crack 67 Figure 30: Effect of tolerance factor on polygon generation time with increasing number of datasets 70 Figure 31: Effect of tolerance factor on polygon rendering time with increasing number of datasets 71 Figure 32: Effect of block size on polygon generation time with increasing number of datasets 72 Figure 33: Hybrid resolution approach 74 Figure 34: Mixed resolution approach 75 Figure 35: DR-MDV: Polygon generation (top) and rendering (bottom) times for isovalue = 0.04 for three criteria 78 Figure 36: DR-AIM - Point vs. Polygons 80 Figure 37: Multi-Resolution for 0.01 (Left) and 0.04 (Right) isovalue. Top row shows isosurfaces at HR, second row shows isosurfaces at LR, third row shows surfaces at LLR and last row shows isosurfaces mixed resolution (HR and LLR) 81 Figure 38: Isosurface generation time for multi resolution 82 Figure 39: Rendering time for multiresolution 83 Figure 40: Quasi-4D Isosurface 85 Figure 41: Quasi-4D Isosurface for magnesium silicate liquid (A) Slice 1 at isovalue of 0.5. (B) Slice 15 at isovalue of 0.3 (C) Slice 15 at isovalue of 0.7 (D) – Slice 25 at the isovalue of 0.7 86 [...]... work is on the multiple dataset scenario, that is, multiple dataset visualization (MDV), which means that more than one dataset are visualized simultaneously in the same visualization [11] MDV is an important concept for the cases 2 where it is not possible to make an inference based on a single dataset and comparison between different datasets is required It allows handling of multiple datasets at the... effective approach for such analysis is visualization of the data In this PhD thesis, we propose an innovative multiple dataset visualization (MDV) approach in which two or more datasets of a given type are rendered concurrently in the same visualization MDV is an important concept for the cases where it is not possible to make an inference based on one dataset, and comparisons between many datasets are... possible to even see volume intersection areas Multiple Dataset Visualization( MDV) Animation Tile Board/Spreadsheets Data Fusion Figure 1: Ways for multiple dataset visualization Tile boarding/spreadsheet scheme with the increased level of interactivity can be effective for MDV [11, 16] and has been effectively used in framework A similar concept for 2D images has been studied widely [17-19] for over a decade... how MDV is significantly different from a normal visualization Extensive research has been done in visualization of a single dataset Most of these techniques are expected to be applicable to the multiple dataset scenario It is important to note that the performance for 3D datasets degrades by a factor of N or higher for N datasets as compared to a single dataset This is mainly due to the increase in memory... fragments and allow to perform lighting, texturing, depth based computations and shading GPU is discussed in detail in section 5.1 2.3 Overview of Visualization Techniques In multiple dataset visualization, we process several datasets simultaneously Two natural approaches for MDV can be a) an extension of the standard visualization methods (available for single dataset) to handle multiple datasets and b) a... before the optimization 123 Figure 66: 3D Wavelet transform with application to texture based volume rendering for solid MgO data 146 Figure 67: 3D Wavelet transform used for Isosurface generation on the solid MgO dataset (a) Original isosurface (b) Isosurface after wavelet transform 147 xiii ABSTRACT Many applications require comparative analysis of multiple datasets... solution for understanding correlation and relationship between such related multiple datasets It provides a way to find subtle differences in these related datasets for understanding the system behavior Figure 3 shows MDV of electron density data Detail analysis and visualization of materials simulation data are given in chapter 6 Similarly, in the medical field, multiple sets of MRI volume data can... number of datasets and probable solutions to maintain interactivity in that environment The challenges in MDV are at the data loading level as well as the visualization level Our technique uses the spreadsheet-based scheme for the user interface 1.4 Challenges In MDV At the first look, visualization of multiple datasets might seem to be a simple extension of the visualization process for a single dataset. .. which are aimed for the fast extraction of isosurfaces from large-scale data as well as time-varying data We have used marching cubes algorithm [4] for extraction of isosurfaces from multiple sets of data at the same time 2.4.2 Marching Cubes Algorithm Marching Cubes [4, 51-55] is an algorithm for rendering isosurfaces in volumetric data We use the octree data structure for representing the dataset In Marching... mathematics, science, engineering and technology Visualization in itself is not a science but proves to be an important tool in understanding the intricacies of the data 1.2 Multiple Dataset Visualization Visualization of scalar data has been studied extensively in the past two decades with appearance of many techniques in the context of the single scalar dataset These techniques can be broadly classified . May 2009 MULTIPLE DATASET VISUALIZATION (MDV) FRAMEWORK FOR SCALAR VOLUME DATA ii To My Parents, Family And My beloved wife, Swati iii ACKNOWLEDGMENTS Foremost of. effective approach for such analysis is visualization of the data. In this PhD thesis, we propose an innovative multiple dataset visualization (MDV) approach in which two or more datasets of a given. available for relatively smaller data sets to get insight into the larger and more complex datasets they generate now. The focus of this work is on the multiple dataset scenario, that is, multiple dataset