PATH TRACING: a NON-BIASED SOLUTION to the RENDERING EQUATION Part 1. Background Introduction
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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 -
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). -
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 -
An Advanced Path Tracing Architecture for Movie Rendering
RenderMan: An Advanced Path Tracing Architecture for Movie Rendering PER CHRISTENSEN, JULIAN FONG, JONATHAN SHADE, WAYNE WOOTEN, BRENDEN SCHUBERT, ANDREW KENSLER, STEPHEN FRIEDMAN, CHARLIE KILPATRICK, CLIFF RAMSHAW, MARC BAN- NISTER, BRENTON RAYNER, JONATHAN BROUILLAT, and MAX LIANI, Pixar Animation Studios Fig. 1. Path-traced images rendered with RenderMan: Dory and Hank from Finding Dory (© 2016 Disney•Pixar). McQueen’s crash in Cars 3 (© 2017 Disney•Pixar). Shere Khan from Disney’s The Jungle Book (© 2016 Disney). A destroyer and the Death Star from Lucasfilm’s Rogue One: A Star Wars Story (© & ™ 2016 Lucasfilm Ltd. All rights reserved. Used under authorization.) Pixar’s RenderMan renderer is used to render all of Pixar’s films, and by many 1 INTRODUCTION film studios to render visual effects for live-action movies. RenderMan started Pixar’s movies and short films are all rendered with RenderMan. as a scanline renderer based on the Reyes algorithm, and was extended over The first computer-generated (CG) animated feature film, Toy Story, the years with ray tracing and several global illumination algorithms. was rendered with an early version of RenderMan in 1995. The most This paper describes the modern version of RenderMan, a new architec- ture for an extensible and programmable path tracer with many features recent Pixar movies – Finding Dory, Cars 3, and Coco – were rendered that are essential to handle the fiercely complex scenes in movie production. using RenderMan’s modern path tracing architecture. The two left Users can write their own materials using a bxdf interface, and their own images in Figure 1 show high-quality rendering of two challenging light transport algorithms using an integrator interface – or they can use the CG movie scenes with many bounces of specular reflections and materials and light transport algorithms provided with RenderMan. -
Getting Started (Pdf)
GETTING STARTED PHOTO REALISTIC RENDERS OF YOUR 3D MODELS Available for Ver. 1.01 © Kerkythea 2008 Echo Date: April 24th, 2008 GETTING STARTED Page 1 of 41 Written by: The KT Team GETTING STARTED Preface: Kerkythea is a standalone render engine, using physically accurate materials and lights, aiming for the best quality rendering in the most efficient timeframe. The target of Kerkythea is to simplify the task of quality rendering by providing the necessary tools to automate scene setup, such as staging using the GL real-time viewer, material editor, general/render settings, editors, etc., under a common interface. Reaching now the 4th year of development and gaining popularity, I want to believe that KT can now be considered among the top freeware/open source render engines and can be used for both academic and commercial purposes. In the beginning of 2008, we have a strong and rapidly growing community and a website that is more "alive" than ever! KT2008 Echo is very powerful release with a lot of improvements. Kerkythea has grown constantly over the last year, growing into a standard rendering application among architectural studios and extensively used within educational institutes. Of course there are a lot of things that can be added and improved. But we are really proud of reaching a high quality and stable application that is more than usable for commercial purposes with an amazing zero cost! Ioannis Pantazopoulos January 2008 Like the heading is saying, this is a Getting Started “step-by-step guide” and it’s designed to get you started using Kerkythea 2008 Echo. -
Production Global Illumination
CIS 497 Senior Capstone Design Project Project Proposal Specification Instructors: Norman I. Badler and Aline Normoyle Production Global Illumination Yining Karl Li Advisor: Norman Badler and Aline Normoyle University of Pennsylvania ABSTRACT For my project, I propose building a production quality global illumination renderer supporting a variety of com- plex features. Such features may include some or all of the following: texturing, subsurface scattering, displacement mapping, deformational motion blur, memory instancing, diffraction, atmospheric scattering, sun&sky, and more. In order to build this renderer, I propose beginning with my existing massively parallel CUDA-based pathtracing core and then exploring methods to accelerate pathtracing, such as GPU-based stackless KD-tree construction, and multiple importance sampling. I also propose investigating and possible implementing alternate GI algorithms that can build on top of pathtracing, such as progressive photon mapping and multiresolution radiosity caching. The final goal of this project is to finish with a renderer capable of rendering out highly complex scenes and anima- tions from programs such as Maya, with high quality global illumination, in a timespan measuring in minutes ra- ther than hours. Project Blog: http://yiningkarlli.blogspot.com While competing with powerhouse commercial renderers 1. INTRODUCTION like Arnold, Renderman, and Vray is beyond the scope of this project, hopefully the end result will still be feature- Global illumination, or GI, is one of the oldest rendering rich and fast enough for use as a production academic ren- problems in computer graphics. In the past two decades, a derer suitable for usecases similar to those of Cornell's variety of both biased and unbaised solutions to the GI Mitsuba render, or PBRT. -
LIGHT TRANSPORT SIMULATION in REFLECTIVE DISPLAYS By
LIGHT TRANSPORT SIMULATION IN REFLECTIVE DISPLAYS by Zhanpeng Feng, B.S.E.E., M.S.E.E. A Dissertation In ELECTRICAL ENGINEERING DOCTOR OF PHILOSOPHY Dr. Brian Nutter Chair of the Committee Dr. Sunanda Mitra Dr. Tanja Karp Dr. Richard Gale Dr. Peter Westfall Peggy Gordon Miller Dean of the Graduate School May, 2012 Copyright 2012, Zhanpeng Feng Texas Tech University, Zhanpeng Feng, May 2012 ACKNOWLEDGEMENTS The pursuit of my Ph.D. has been a rather long journey. The journey started when I came to Texas Tech ten years ago, then took a change in direction when I went to California to work for Qualcomm in 2006. Over the course, I am privileged to have met the most amazing professionals in Texas Tech and Qualcomm. Without them I would have never been able to finish this dissertation. I begin by thanking my advisor, Dr. Brian Nutter, for introducing me to the brilliant world of research, and teaching me hands on skills to actually get something done. Dr. Nutter sets an example of excellence that inspired me to work as an engineer and researcher for my career. I would also extend my thanks to Dr. Mitra for her breadth and depth of knowledge; to Dr. Karp for her scientific rigor; to Dr. Gale for his expertise in color science and sense of humor; and to Dr. Westfall, for his great mind in statistics. They have provided me invaluable advice throughout the research. My colleagues and supervisors in Qualcomm also gave tremendous support and guidance along the path. Tom Fiske helped me establish my knowledge in optics from ground up and taught me how to use all the tools for optical measurements. -
The Photon Mapping Method
7 The Photon Mapping Method “I get by with a little help from my friends.” —John Lennon, 1940–1980 HOTON mapping is a practical approach for computing global illumination within complex P environments. Much like irradiance caching methods, photon mapping caches and reuses illumination information in the scene for efficiency. Photon mapping has also been successfully applied for computing lighting within, and in the presence of, participating media. In this chapter we briefly introduce the photon mapping technique. This sets the foundation for our contributions in the next chapter, which make volumetric photon mapping practical. 7.1 Algorithm Overview Photon mapping, introduced by Jensen[1995; 1996; 1997; 1998; 2001], is a practical approach for computing global illumination. At a high level, the algorithm consists of two main steps: Algorithm 7.1:PHOTONMAPPING() 1 PHOTONTRACING(); 2 RENDERUSINGPHOTONMAP(); In the first step, a lighting simulation is performed by tracing packets of energy, or photons, from light sources and storing these photons as they scatter within the scene. This processes 119 120 Algorithm 7.2:PHOTONTRACING() 1 n 0; e Æ 2 repeat 3 (l, pdf (l)) = CHOOSELIGHT(); 4 (xp , ~!p , ©p ) = GENERATEPHOTON(l ); ©p 5 TRACEPHOTON(xp , ~!p , pdf (l) ); 6 n 1; e ÅÆ 7 until photon map full ; 1 8 Scale power of all photons by ; ne results in a set of photon maps, which can be used to efficiently query lighting information. In the second pass, the final image is rendered using Monte Carlo ray tracing. This rendering step is made more efficient by exploiting the lighting information cached in the photon map. -
Interactive Distributed Ray Tracing of Highly Complex Models Ingo Wald, Philipp Slusallek, Carsten Benthin Computer Graphics Group
Interactive Distributed Ray Tracing of Highly Complex Models Ingo Wald, Philipp Slusallek, Carsten Benthin Computer Graphics Group, Saarland University, Saarbruecken, Germany g fwald,slusallek,benthin @graphics.cs.uni-sb.de Abstract. Many disciplines must handle the creation, visualization, and manip- ulation of huge and complex 3D environments. Examples include large structural and mechanical engineering projects dealing with entire cars, ships, buildings, and processing plants. The complexity of such models is usually far beyond the interactive rendering capabilities of todays 3D graphics hardware. Previous ap- proaches relied on costly preprocessing for reducing the number of polygons that need to be rendered per frame but suffered from excessive precomputation times — often several days or even weeks. In this paper we show that using a highly optimized software ray tracer we are able to achieve interactive rendering performance for models up to 50 million triangles including reflection and shadow computations. The necessary prepro- cessing has been greatly simplified and accelerated by more than two orders of magnitude. Interactivity is achieved with a novel approach to distributed render- ing based on coherent ray tracing. A single copy of the scene database is used together with caching of BSP voxels in the ray tracing clients. 1 Introduction The performance of todays graphics hardware has been increased dramati- cally over the last few years. Today many graphics applications can achieve interactive rendering performance even on standard PCs. However, there are also many applications that must handle the creation, visualization, and manipulation of huge and complex 3D environments often containing several tens of millions of polygons [1, 9].