A Practical Guide to Global Illumination Using Photon Maps
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Photon Mapping Assignment
Photon Mapping Assignment 15-864 Advanced Computer Graphics, Carnegie Mellon University Instructor: Doug L. James TA: Christopher Twigg Introduction sampling to emit photons of equal intensity from the diffuse area light source. Use the ray tracer’s functionality to propagate photons In this assignment you will implement (portions of) a photon map- (reflect, transmit and absorb) throughout the scene. To maintain ping renderer. For simplicity, we will only consider scenes with a photons of similar intensity, use Russian roulette [Arvo and Kirk single area light source, and assume surfaces are diffuse, or purely 1990] to determine if photons are absorbed (diffuse), transmitted specular (e.g., mirror or glass). To generate images for testing and (transparent), or reflected at surfaces. Use Schlick’s approximation grading, a test scene will be provided for you on the class website; to Fresnel’s specular reflection coefficient to determine the prob- this will be a very simple consisting of the Cornell box, an area ability of transmission and reflection at specular interfaces, e.g., light source, and specular spheres. Although a brief explanation of glass. Store the photons in the photon map using Jensen’s kd-tree what needs to be done is given below, further implementation de- data structure implementation (provided on the web page). Once tails can be found in [Jensen 2001; Jensen 1996], as well as other these photons are stored, the data structure can compute the filtered ray tracing [Shirley 2000], Monte Carlo [Jensen 2003], and global irradiance estimates you need later. illumination texts [Dutre´ et al. 2003]. Build the Caustic Photon Map (20 points): The high- Getting Started: Familiarize yourself with resolution caustic photon map represents the LS+D paths, and it the ray tracer is therefore only necessary to emit photons toward specular objects when computing the caustic photon map. -
CUDA-SCOTTY Fast Interactive CUDA Path Tracer Using Wide Trees and Dynamic Ray Scheduling
15-618: Parallel Computer Architecture and Programming CUDA-SCOTTY Fast Interactive CUDA Path Tracer using Wide Trees and Dynamic Ray Scheduling “Golden Dragon” TEAM MEMBERS Sai Praveen Bangaru (Andrew ID: saipravb) Sam K Thomas (Andrew ID: skthomas) Introduction Path tracing has long been the select method used by the graphics community to render photo-realistic images. It has found wide uses across several industries, and plays a major role in animation and filmmaking, with most special effects rendered using some form of Monte Carlo light transport. It comes as no surprise, then, that optimizing path tracing algorithms is a widely studied field, so much so, that it has it’s own top-tier conference (HPG; High Performance Graphics). There are generally a whole spectrum of methods to increase the efficiency of path tracing. Some methods aim to create better sampling methods (Metropolis Light Transport), while others try to reduce noise in the final image by filtering the output (4D Sheared transform). In the spirit of the parallel programming course 15-618, however, we focus on a third category: system-level optimizations and leveraging hardware and algorithms that better utilize the hardware (Wide Trees, Packet tracing, Dynamic Ray Scheduling). Most of these methods, understandably, focus on the ray-scene intersection part of the path tracing pipeline, since that is the main bottleneck. In the following project, we describe the implementation of a hybrid non-packet method which uses Wide Trees and Dynamic Ray Scheduling to provide an 80x improvement over a 8-threaded CPU implementation. Summary Over the course of roughly 3 weeks, we studied two non-packet BVH traversal optimizations: Wide Trees, which involve non-binary BVHs for shallower BVHs and better Warp/SIMD Utilization and Dynamic Ray Scheduling which involved changing our perspective to process rays on a per-node basis rather than processing nodes on a per-ray basis. -
Practical Path Guiding for Efficient Light-Transport Simulation
Eurographics Symposium on Rendering 2017 Volume 36 (2017), Number 4 P. Sander and M. Zwicker (Guest Editors) Practical Path Guiding for Efficient Light-Transport Simulation Thomas Müller1;2 Markus Gross1;2 Jan Novák2 1ETH Zürich 2Disney Research Vorba et al. MSE: 0.017 Reference Ours (equal time) MSE: 0.018 Training: 5.1 min Training: 0.73 min Rendering: 4.2 min, 8932 spp Rendering: 4.2 min, 11568 spp Figure 1: Our method allows efficient guiding of path-tracing algorithms as demonstrated in the TORUS scene. We compare equal-time (4.2 min) renderings of our method (right) to the current state-of-the-art [VKv∗14, VK16] (left). Our algorithm automatically estimates how much training time is optimal, displays a rendering preview during training, and requires no parameter tuning. Despite being fully unidirectional, our method achieves similar MSE values compared to Vorba et al.’s method, which trains bidirectionally. Abstract We present a robust, unbiased technique for intelligent light-path construction in path-tracing algorithms. Inspired by existing path-guiding algorithms, our method learns an approximate representation of the scene’s spatio-directional radiance field in an unbiased and iterative manner. To that end, we propose an adaptive spatio-directional hybrid data structure, referred to as SD-tree, for storing and sampling incident radiance. The SD-tree consists of an upper part—a binary tree that partitions the 3D spatial domain of the light field—and a lower part—a quadtree that partitions the 2D directional domain. We further present a principled way to automatically budget training and rendering computations to minimize the variance of the final image. -
Path Tracing
Path Tracing Steve Rotenberg CSE168: Rendering Algorithms UCSD, Spring 2017 Irradiance Circumference of a Circle • The circumference of a circle of radius r is 2πr • In fact, a radian is defined as the angle you get on an arc of length r • We can represent the circumference of a circle as an integral 2휋 푐푖푟푐 = 푟푑휑 0 • This is essentially computing the length of the circumference as an infinite sum of infinitesimal segments of length 푟푑휑, over the range from 휑=0 to 2π Area of a Hemisphere • We can compute the area of a hemisphere by integrating ‘rings’ ranging over a second angle 휃, which ranges from 0 (at the north pole) to π/2 (at the equator) • The area of a ring is the circumference of the ring times the width 푟푑휃 • The circumference is going to be scaled by sin휃 as the rings are smaller towards the top of the hemisphere 휋 2 2휋 2 2 푎푟푒푎 = sin 휃 푟 푑휑 푑휃 = 2휋푟 0 0 Hemisphere Integral 휋 2 2휋 2 푎푟푒푎 = sin 휃 푟 푑휑 푑휃 0 0 • We are effectively computing an infinite summation of tiny rectangular area elements over a two dimensional domain. Each element has dimensions: sin 휃 푟푑휑 × 푟푑휃 Irradiance • Now, let’s assume that we are interested in computing the total amount of light arriving at some point on a surface • We are essentially integrating over all possible directions in the hemisphere above the surface (assuming it’s opaque and we’re not receiving translucent light from below the surface) • We are integrating the light intensity (or radiance) coming in from every direction • The total incoming radiance over all directions in the hemisphere -
POV-Ray Reference
POV-Ray Reference POV-Team for POV-Ray Version 3.6.1 ii Contents 1 Introduction 1 1.1 Notation and Basic Assumptions . 1 1.2 Command-line Options . 2 1.2.1 Animation Options . 3 1.2.2 General Output Options . 6 1.2.3 Display Output Options . 8 1.2.4 File Output Options . 11 1.2.5 Scene Parsing Options . 14 1.2.6 Shell-out to Operating System . 16 1.2.7 Text Output . 20 1.2.8 Tracing Options . 23 2 Scene Description Language 29 2.1 Language Basics . 29 2.1.1 Identifiers and Keywords . 30 2.1.2 Comments . 34 2.1.3 Float Expressions . 35 2.1.4 Vector Expressions . 43 2.1.5 Specifying Colors . 48 2.1.6 User-Defined Functions . 53 2.1.7 Strings . 58 2.1.8 Array Identifiers . 60 2.1.9 Spline Identifiers . 62 2.2 Language Directives . 64 2.2.1 Include Files and the #include Directive . 64 2.2.2 The #declare and #local Directives . 65 2.2.3 File I/O Directives . 68 2.2.4 The #default Directive . 70 2.2.5 The #version Directive . 71 2.2.6 Conditional Directives . 72 2.2.7 User Message Directives . 75 2.2.8 User Defined Macros . 76 3 Scene Settings 81 3.1 Camera . 81 3.1.1 Placing the Camera . 82 3.1.2 Types of Projection . 86 3.1.3 Focal Blur . 88 3.1.4 Camera Ray Perturbation . 89 3.1.5 Camera Identifiers . 89 3.2 Atmospheric Effects . -
Surface Recovery: Fusion of Image and Point Cloud
Surface Recovery: Fusion of Image and Point Cloud Siavash Hosseinyalamdary Alper Yilmaz The Ohio State University 2070 Neil avenue, Columbus, Ohio, USA 43210 pcvlab.engineering.osu.edu Abstract construct surfaces. Implicit (or volumetric) representation of a surface divides the three dimensional Euclidean space The point cloud of the laser scanner is a rich source of to voxels and the value of each voxel is defined based on an information for high level tasks in computer vision such as indicator function which describes the distance of the voxel traffic understanding. However, cost-effective laser scan- to the surface. The value of every voxel inside the surface ners provide noisy and low resolution point cloud and they has negative sign, the value of the voxels outside the surface are prone to systematic errors. In this paper, we propose is positive and the surface is represented as zero crossing two surface recovery approaches based on geometry and values of the indicator function. Unfortunately, this repre- brightness of the surface. The proposed approaches are sentation is not applicable to open surfaces and some mod- tested in realistic outdoor scenarios and the results show ifications should be applied to reconstruct open surfaces. that both approaches have superior performance over the- The least squares and partial differential equations (PDE) state-of-art methods. based approaches have also been developed to implicitly re- construct surfaces. The moving least squares(MLS) [22, 1] and Poisson surface reconstruction [16], has been used in 1. Introduction this paper for comparison, are particularly popular. Lim and Haron review different surface reconstruction techniques in Point cloud is a valuable source of information for scene more details [20]. -
Megakernels Considered Harmful: Wavefront Path Tracing on Gpus
Megakernels Considered Harmful: Wavefront Path Tracing on GPUs Samuli Laine Tero Karras Timo Aila NVIDIA∗ Abstract order to handle irregular control flow, some threads are masked out when executing a branch they should not participate in. This in- When programming for GPUs, simply porting a large CPU program curs a performance loss, as masked-out threads are not performing into an equally large GPU kernel is generally not a good approach. useful work. Due to SIMT execution model on GPUs, divergence in control flow carries substantial performance penalties, as does high register us- The second factor is the high-bandwidth, high-latency memory sys- age that lessens the latency-hiding capability that is essential for the tem. The impressive memory bandwidth in modern GPUs comes at high-latency, high-bandwidth memory system of a GPU. In this pa- the expense of a relatively long delay between making a memory per, we implement a path tracer on a GPU using a wavefront formu- request and getting the result. To hide this latency, GPUs are de- lation, avoiding these pitfalls that can be especially prominent when signed to accommodate many more threads than can be executed in using materials that are expensive to evaluate. We compare our per- any given clock cycle, so that whenever a group of threads is wait- formance against the traditional megakernel approach, and demon- ing for a memory request to be served, other threads may be exe- strate that the wavefront formulation is much better suited for real- cuted. The effectiveness of this mechanism, i.e., the latency-hiding world use cases where multiple complex materials are present in capability, is determined by the threads’ resource usage, the most the scene. -
Distribution Ray Tracing Academic Press, 1989
Reading Required: ® Shirley, 13.11, 14.1-14.3 Further reading: ® A. Glassner. An Introduction to Ray Tracing. Distribution Ray Tracing Academic Press, 1989. [In the lab.] ® Robert L. Cook, Thomas Porter, Loren Carpenter. “Distributed Ray Tracing.” Computer Graphics Brian Curless (Proceedings of SIGGRAPH 84). 18 (3) . pp. 137- CSE 557 145. 1984. Fall 2013 ® James T. Kajiya. “The Rendering Equation.” Computer Graphics (Proceedings of SIGGRAPH 86). 20 (4) . pp. 143-150. 1986. 1 2 Pixel anti-aliasing BRDF The diffuse+specular parts of the Blinn-Phong illumination model are a mapping from light to viewing directions: ns L+ V I=I B k(N⋅ L ) +k N ⋅ L d s L+ V + = IL f r (,L V ) The mapping function fr is often written in terms of ω No anti-aliasing incoming (light) directions in and outgoing (viewing) ω directions out : ωω ωω→ fr(in ,out) or f r ( in out ) This function is called the Bi-directional Reflectance Distribution Function (BRDF ). ω Here’s a plot with in held constant: f (ω , ω ) ω r in out in Pixel anti-aliasing All of this assumes that inter-reflection behaves in a mirror-like fashion… BRDF’s can be quite sophisticated… 3 4 Light reflection with BRDFs Simulating gloss and translucency BRDF’s exhibit Helmholtz reciprocity: The mirror-like form of reflection, when used to f(ωω→)= f ( ω → ω ) rinout r out in approximate glossy surfaces, introduces a kind of That means we can take two equivalent views of aliasing, because we are under-sampling reflection ω ω (and refraction). -
Experimental Validation of Autodesk 3Ds Max Design 2009 and Daysim
Experimental Validation of Autodesk® 3ds Max® Design 2009 and Daysim 3.0 NRC Project # B3241 Submitted to: Autodesk Canada Co. Media & Entertainment Submitted by: Christoph Reinhart1,2 1) National Research Council Canada - Institute for Research in Construction (NRC-IRC) Ottawa, ON K1A 0R6, Canada (2001-2008) 2) Harvard University, Graduate School of Design Cambridge, MA 02138, USA (2008 - ) February 12, 2009 B3241.1 Page 1 Table of Contents Abstract ....................................................................................................................................... 3 1 Introduction .......................................................................................................................... 3 2 Methodology ......................................................................................................................... 5 2.1 Daylighting Test Cases .................................................................................................... 5 2.2 Daysim Simulations ....................................................................................................... 12 2.3 Autodesk 3ds Max Design Simulations ........................................................................... 13 3 Results ................................................................................................................................ 14 3.1 Façade Illuminances ...................................................................................................... 14 3.2 Base Case (TC1) and Lightshelf (TC2) -
Adjoints and Importance in Rendering: an Overview
IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS, VOL. 9, NO. 3, JULY-SEPTEMBER 2003 1 Adjoints and Importance in Rendering: An Overview Per H. Christensen Abstract—This survey gives an overview of the use of importance, an adjoint of light, in speeding up rendering. The importance of a light distribution indicates its contribution to the region of most interest—typically the directly visible parts of a scene. Importance can therefore be used to concentrate global illumination and ray tracing calculations where they matter most for image accuracy, while reducing computations in areas of the scene that do not significantly influence the image. In this paper, we attempt to clarify the various uses of adjoints and importance in rendering by unifying them into a single framework. While doing so, we also generalize some theoretical results—known from discrete representations—to a continuous domain. Index Terms—Rendering, adjoints, importance, light, ray tracing, global illumination, participating media, literature survey. æ 1INTRODUCTION HE use of importance functions started in neutron importance since it indicates how much the different parts Ttransport simulations soon after World War II. Im- of the domain contribute to the solution at the most portance was used (in different disguises) from 1983 to important part. Importance is also known as visual accelerate ray tracing [2], [16], [27], [78], [79]. Smits et al. [67] importance, view importance, potential, visual potential, value, formally introduced the use of importance for global -
Real-Time Global Illumination with Photon Mapping Niklas Smal and Maksim Aizenshtein UL Benchmarks
CHAPTER 24 Real-Time Global Illumination with Photon Mapping Niklas Smal and Maksim Aizenshtein UL Benchmarks ABSTRACT Indirect lighting, also known as global illumination, is a crucial effect in photorealistic images. While there are a number of effective global illumination techniques based on precomputation that work well with static scenes, including global illumination for scenes with dynamic lighting and dynamic geometry remains a challenging problem. In this chapter, we describe a real-time global illumination algorithm based on photon mapping that evaluates several bounces of indirect lighting without any precomputed data in scenes with both dynamic lighting and fully dynamic geometry. We explain both the pre- and post-processing steps required to achieve dynamic high-quality illumination within the limits of a real- time frame budget. 24.1 INTRODUCTION As the scope of what is possible with real-time graphics has grown with the advancing capabilities of graphics hardware, scenes have become increasingly complex and dynamic. However, most of the current real-time global illumination algorithms (e.g., light maps and light probes) do not work well with moving lights and geometry due to these methods’ dependence on precomputed data. In this chapter, we describe an approach based on an implementation of photon mapping [7], a Monte Carlo method that approximates lighting by first tracing paths of light-carrying photons in the scene to create a data structure that represents the indirect illumination and then using that structure to estimate indirect light at points being shaded. See Figure 24-1. Photon mapping has a number of useful properties, including that it is compatible with precomputed global illumination, provides a result with similar quality to current static techniques, can easily trade off quality and computation time, and requires no significant artist work. -
Open Source Software for Daylighting Analysis of Architectural 3D Models
19th International Congress on Modelling and Simulation, Perth, Australia, 12–16 December 2011 http://mssanz.org.au/modsim2011 Open Source Software for Daylighting Analysis of Architectural 3D Models Terrance Mc Minn a a Curtin University of Technology School of Built Environment, Perth, Australia Email: [email protected] Abstract:This paper examines the viability of using open source software for the architectural analysis of solar access and over shading of building projects. For this paper open source software also includes freely available closed source software. The Computer Aided Design software – Google SketchUp (Free) while not open source, is included as it is freely available, though with restricted import and export abilities. A range of software tools are used to provide an effective procedure to aid the Architect in understanding the scope of sun penetration and overshadowing on a site and within a project. The technique can be also used lighting analysis of both external (to the building) as well as for internal spaces. An architectural model built in SketchUp (free) CAD software is exported in two different forms for the Radiance Lighting Simulation Suite to provide the lighting analysis. The different exports formats allow the 3D CAD model to be accessed directly via Radiance for full lighting analysis or via the Blender Animation program for a graphical user interface limited option analysis. The Blender Modelling Environment for Architecture (BlendME) add-on exports the model and runs Radiance in the background. Keywords:Lighting Simulation, Open Source Software 3226 McMinn, T., Open Source Software for Daylighting Analysis of Architectural 3D Models INTRODUCTION The use of daylight in buildings has the potential for reduction in the energy demands and increasing thermal comfort and well being of the buildings occupants (Cutler, Sheng, Martin, Glaser, et al., 2008), (Webb, 2006), (Mc Minn & Karol, 2010), (Yancey, n.d.) and others.