Soft Shadows, Curved Surfaces and Perceptual Sensitivity: Advanced Methods for Improving Realism in Real-time Rendering

Transcription

1 Arbeitsberichte des Department Informatik Friedrich-Alexander-Universität Erlangen Nürnberg Band 42 Nummer 2 Dezember 2009 Michael Schwarz Soft Shadows, Curved Surfaces and Perceptual Sensitivity: Advanced Methods for Improving Realism in Real-time Rendering Dissertation Herausgeber: Т. Brinda, M. Dal Cin, D. Fey, R. German, G. Görz, G. Greiner, U. Herzog, F. Hofmann, J. Hornegger, К. Leeb, R. Lenz, P. Mertens, K. Meyer-Wegener, H. Müller, H. Niemann, E. Noth, Ch. Pflaum, M. Philippsen, D. Riehle, U. Rüde, F. Saglietti, H. J. Schneider, W. Schroder-Preikschat, M. Stamminger, H. Stoyan, J. Teich, R. Wanka, H. Wedekind Die Reihe der Arbeitsberichte des Department Informatik (ehem. Institut für Mathematische Maschinen und Datenverarbeitung) der Universität Erlangen-Nürnberg erscheint seit Begründet von Prof. Dr. Dr. h. с mult. Wolfgang Händler

2 Contents Abstract v 1 Introduction Contributions Outline 3 2 Real-time rendering Rendering pipeline Graphics hardware GPGPU and compute APIs Level-of-detail approaches Kinds of realism 11 I Real-time soft shadows 3 Overview of real-time soft shadows Soft shadows Real-time approaches Image-based approaches Geometry-based approaches Hybrid approaches Approaches for low-frequency environmental lights Discussion Quasi-interactive approaches for accurate soft shadows 26 4 Soft shadow mapping with occluder backprojection Basic approach Visibility determination with occlusion bitmasks Occlusion bitmasks Advanced applications Discussion Acceleration structures Multi-scale shadow map Hybrid Y shadow map Discussion 44 ix

3 x CONTENTS 4.4 Occluder approximations Microquads Approximate occlusion bitmasks for microquads Microtris Exact occlusion bitmasks for microquads and microtris Discussion Coarser occluder approximations Microrects as a generalization of micropatches Construction of microrects at coarser levels Discussion of microrects Biasing problems Visibility interpolation for multisample support Results and conclusion 64 5 Level of quality for soft shadows Possible approaches ' Multiple algorithms producing different quality Geometric occluder LOD Sparse visibility sampling Intrinsic algorithm parameters Smooth quality variation for soft shadow mapping Approach Discussion Results 76 II Rendering of curved surfaces 6 Fundamentals of curved surfaces Bezier surfaces Bezier patches Bezier triangles PN triangles Spline surfaces Subdivision surfaces Direct evaluation Approximation using Bezier surfaces Algebraic surfaces GPU-based raycasting Rendering approaches Tessellation Raycasting Direct rasterization Adaptive tessellation Objectives Ill 7.2 Recursive refinement Refinement criteria 114

4 CONTENTS xi Refining a rectangular domain Refining a triangular domain Locally handling cracks GPU-based implementations Discussion Tessellation patterns Patterns for rectangular domains Patterns for triangular domains Transition regions Fast pattern generation Determining tessellation factors Bounding screen-space triangle sizes Bounding the approximation error Rational Bezier patches Bezier triangles PN triangles Rendering of refinement patterns GPU-based methods Connection patterns for dyadic tessellation of PN triangle meshes Instanced rendering Number of refinement patterns Direct hardware support Patch-parallel on-the-fly tessellation CudaTess framework for adaptive tessellation Example: bicubic rational Bezier patches Example: PN triangles Discussion Comparison to rendering refinement patterns 162 III Perception-aware rendering 8 Fundamentals of human visual perception Human perception and psychophysics Human visual system Color and color appearance Visual attention Perceptually motivated rendering Building blocks for computational models Contrast sensitivity functions Visual masking Multi-channel decomposition Vision models and visual difference metrics Overview of perceptually motivated applications Real-time threshold maps Interactive perceptual rendering pipeline 188

5 xii CONTENTS 9.6 Problems in applying perceptual results Visual popping Popping and related treatment approaches Aspects of perceiving popping Perceptually motivated popping predictor Overview Discussion Spatio-velocity color vision model Popping regions Examples User study Experiment I: direct evaluation with simple object Experiment II: indirect evaluation with real-world examples Conclusion Conclusion 211 Bibliography 213