Rochester Institute of Technology RIT Scholar Works Theses Thesis/Dissertation Collections 2011 Scientific visualization using Pixar's RenderMan John Lukasiewicz Follow this and additional works at: http://scholarworks.rit.edu/theses Recommended Citation Lukasiewicz, John, "Scientific visualization using Pixar's RenderMan" (2011). Thesis. Rochester Institute of Technology. Accessed from This Thesis is brought to you for free and open access by the Thesis/Dissertation Collections at RIT Scholar Works. It has been accepted for inclusion in Theses by an authorized administrator of RIT Scholar Works. For more information, please contact [email protected]. Scientific Visualization Using Pixar's RenderMan John Lukasiewicz Computer Science M.S. Thesis Department of Computer Science Golisano College of Computing and Information Sciences Rochester Institute of Technology Rochester, New York June 29, 2011 Approved by: Advisor: Professor Hans-Peter Bischof, Ph.D. Reader: Professor Reynold Bailey, Ph.D. Observer: Professor Joe Geigel, Ph.D. Abstract This thesis will attempt to visualize astrophysical data that is proprocessed and formatted by the Spiegel software using Pixar's RenderMan. The output will consist of a large set of points and data associated with each point. The goal is to create images that are both informative and aesthetically pleasing to the viewer. This has been done many times before with software rendering and APIs such as OpenGL or JOGL. This thesis will use Pixar's Photorealistic RenderMan, or PRMan for short, as a renderer. PRMan is an industry proven standard renderer that is based on the RenderMan Interface Specification which has been in development since 1989. The original version was released in September of 1989 and the latest specification, version 3.2 was published in 2005. Since aesthetics is a subjective quality based on the viewers' preference, the only way to determine if an image is aesthetically pleasing is to survey a general population. The thesis includes an experiment to assess the quality of the new renders. i Acknowledgements Thanks goes out to my Advisor, Dr. Hans-Peter Bischof for allowing me to work on the Spiegel project and pushing me to do my best while working on the project. I would also like to thank all the Professors who taught computer graphics, including Professor Joe Geigel, Professor Reynold Bailey and Professor Warren Carithers for giving me the basis and fundamental knowledge which enabled me to write this thesis. I would also like to acknowledge my friends who I was able to run ideas back and fourth and get feedback for the render images and progress I was making. I would also like to acknowledge the students in the REU program who wrote the initial RenderMan framework in Spiegel. Much of their code was used in the plugins created in this thesis. I would also like to thank my parents and family for their prayers and support for me through all these years. They always did everything they could to help me get to where I am today. ii List of Figures 1 Example Spiegel Script . 12 2 RGBCube................................... 15 3 RGB Addition . 15 4 HUE Wheel . 16 5 HSV Cone . 16 6 HLS Cone . 17 7 Corner Grid Points . 18 8 Corner Gradients . 19 9 Corner Vectors . 19 10 Noise Interpolation Curves . 20 11 Noise Interpolation in 3d . 21 12 Turbulence Example . 22 13 Marching Cubes Cases . 24 14 Ball Pivoting Example in 2d . 26 15 Ball Pivoting . 27 16 IPD Influence Region . 29 17 Phong Interpolation . 33 18 Mach Banding . 34 19 Phong Components . 35 20 Gooch Shaded Gravity Wave . 37 21 Wispy Clouds . 39 22 Nebula 1 . 42 23 Gravity Wave Density Points H . 43 24 Gravity Wave Density Points L . 44 25 Gravity Wave Density Spheres . 45 26 Gravity Wave Polygonzied . 46 27 Torus points . 48 28 Torus polygonzied . 49 29 Survey Image . 50 30 Reference Image . 51 iii Contents Abstract . .i Acknowledgments . ii List of Figures . iii Table of Contents . iv 1 Introduction 1 1.1 Problem Statement . .2 1.1.1 Applications Used . .2 1.2 Thesis Outline . .3 2 Previous Work in Spiegel 5 2.1 OpenGL . .5 2.1.1 Design . .5 2.1.2 OpenGL Pipeline . .5 2.1.3 RenderMan REYES Pipeline . .6 2.1.4 Differences Between OpenGL and Reyes . .7 2.2 Motivations for using RenderMan . .8 2.2.1 OpenGL Hardware Compatiblity . .8 2.2.2 RenderMan Filters . .8 2.2.3 RenderMan Shaders and Shading Language . .9 2.2.4 Aliasing . 10 2.3 Previous Spiegel RenderMan Pipeline . 10 2.3.1 Design . 10 2.4 Modifications to Pipeline . 10 2.4.1 New Plugins Written . 11 2.4.2 Modular Design . 11 2.4.3 RIB Archives to Speed Up Renders . 11 2.4.4 Usage of Pipeline in Spiegel . 11 3 Algorithms 14 3.1 Color Models . 14 3.1.1 RGB Color Model . 15 3.1.2 HSV Color Model . 15 3.1.3 HLS Color Model . 17 3.2 Perlin Noise . 17 3.2.1 Noise in Two Dimensions . 18 3.2.2 Noise in Three Dimensions . 21 3.2.3 Turbulence and Fractal Noise . 21 3.3 Creating a Surface from Equally Distributed Points . 22 3.3.1 Marching Cubes . 23 3.3.2 Marching Tetrahedra . 25 3.4 Creating a Surface from Unequally Distributed Points . 25 3.4.1 Ball-Pivoting Algorithm . 25 3.4.2 Intrinsic Property Driven Algorithm . 28 3.4.3 Pivoting Circles Algorithm . 30 iv 4 Implementation 32 4.1 RenderMan Pipeline . 32 4.1.1 Taking Advantage of the Pipeline with RIB Archives . 32 4.2 RenderMan Shaders . 33 4.2.1 Phong Shader . 33 4.2.2 Gooch Shader . 35 4.2.3 Star Shader . 38 4.2.4 Nebula Cloud Shader . 39 4.3 Nebula Render . 41 4.4 Gravitational Wave . 42 4.4.1 Implementation of Marching Cubes Algorithm . 43 4.4.2 Optimizing RenderMan Memory Usage through Delayed Read Archives 47 4.5 Surface Reconstruction of a Point Cloud . 47 4.5.1 Polygonizing a Point Cloud of a Surface . 47 5 Results 49 5.1 Data Generation and Render Benchmarks . 49 5.1.1 Nebula Render . 49 5.1.2 Survey . 50 5.1.3 Gravitational Wave with Marching Cubes . 52 5.1.4 Surface Polygonization . 53 6 Conclusion 54 6.1 Nebula Poll Results . 54 6.2 Future Work . 54 Bibliography 56 v 1 Introduction Scientific visualization is a very important field which enables researchers to gain a more broad understanding and idea of what large sets of n-dimensional data look like. Scientific visualization allows one to take a large amount of information and see it all at once. The data represented by visualization could be graphs, abstract quantities or changes over time. It could also be actual physical and engineering data gathered through various means or theoretical concepts. An example would be volume rendering an MRI or in the case of this thesis; gravitational waves. Scientific visualization is a very broad field that is usually applied to an existing project or research data. Most visualization systems and techniques have been created specifically for one type of visualization. For example, constrained inverse volume rendering[18], or MacVis[13]. Spiegel, on the other hand, is a general purpose visualization system which is designed to meet future visualization needs that are currently not supported.[4] A similar implementation to the RenderMan Shading Language was used to render astrophysical data before. In their paper, Corrie et al. write about Data Shaders that were designed for visualizing volumetric data.[8] They describe an extension to the existing types of shaders in PRMan called a Data Shader. Data Shaders are designed to perform the shading and classification of the sub-volume around a sample point in a volume data set. The shader does not actually work on RenderMan, instead it is implemented on a programmable volume rendering system based on cap vol[8], a volume renderer that has been developed at the Australian National University. This thesis modifies a RenderMan pipeline in a visualization software, Spiegel, that was developed at RIT and implements Spiegel plugins to render three different astro- physical objects using the RenderMan pipeline. The objects are a nebula, gravitational wave and a point cloud in order to evaluate and analyze the results compared to previous results that were rendered in OpenGL. Several plugins were developed to visualize the objects. The objects themselves are contained in text files that contain point data which 1 is read in by Spiegel, which.