Ray Tracing and Shading
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The Diffuse Reflecting Power of Various Substances 1
. THE DIFFUSE REFLECTING POWER OF VARIOUS SUBSTANCES 1 By W. W. Coblentz CONTENTS Page I. Introduction . 283 II. Summary of previous investigations 288 III. Apparatus and methods 291 1 The thermopile 292 2. The hemispherical mirror 292 3. The optical system 294 4. Regions of the spectrum examined 297 '. 5. Corrections to observations 298 IV. Reflecting power of lampblack 301 V. Reflecting power of platinum black 305 VI. Reflecting power of green leaves 308 VII. Reflecting power of pigments 311 VIII. Reflecting power of miscellaneous substances 313 IX. Selective reflection and emission of white paints 315 X. Summary 318 Note I. —Variation of the specular reflecting power of silver with angle 319 of incidence I. INTRODUCTION In all radiometric work involving the measurement of radiant energy in absolute value it is necessary to use an instrument that intercepts or absorbs all the incident radiations; or if that is impracticable, it is necessary to know the amount that is not absorbed. The instruments used for intercepting and absorbing radiant energy are usually constructed in the form of conical- shaped cavities which are blackened with lampblack, the expecta- tion being that, after successive reflections within the cavity, the amount of energy lost by passing out through the opening is reduced to a negligible value. 1 This title is used in order to distinguish the reflection of matte surfaces from the (regular) reflection of polished surfaces. The paper gives also data on the specular reflection of polished silver for different angles of incidence, but it seemed unnecessary to include it in the title. -
Ray-Tracing in Vulkan.Pdf
Ray-tracing in Vulkan A brief overview of the provisional VK_KHR_ray_tracing API Jason Ekstrand, XDC 2020 Who am I? ▪ Name: Jason Ekstrand ▪ Employer: Intel ▪ First freedesktop.org commit: wayland/31511d0e dated Jan 11, 2013 ▪ What I work on: Everything Intel but not OpenGL front-end – src/intel/* – src/compiler/nir – src/compiler/spirv – src/mesa/drivers/dri/i965 – src/gallium/drivers/iris 2 Vulkan ray-tracing history: ▪ On March 19, 2018, Microsoft announced DirectX Ray-tracing (DXR) ▪ On September 19, 2018, Vulkan 1.1.85 included VK_NVX_ray_tracing for ray- tracing on Nvidia RTX GPUs ▪ On March 17, 2020, Khronos released provisional cross-vendor extensions: – VK_KHR_ray_tracing – SPV_KHR_ray_tracing ▪ Final cross-vendor Vulkan ray-tracing extensions are still in-progress within the Khronos Vulkan working group 3 Overview: My objective with this presentation is mostly educational ▪ Quick overview of ray-tracing concepts ▪ Walk through how it all maps to the Vulkan ray-tracing API ▪ Focus on the provisional VK/SPV_KHR_ray_tracing extension – There are several details that will likely be different in the final extension – None of that is public yet, sorry. – The general shape should be roughly the same between provisional and final ▪ Not going to discuss details of ray-tracing on Intel GPUs 4 What is ray-tracing? All 3D rendering is a simulation of physical light 6 7 8 Why don't we do all 3D rendering this way? The primary problem here is wasted rays ▪ The chances of a random photon from the sun hitting your scene is tiny – About 1 in -
Some Diffuse Reflection Problems in Radiation Aerodynamics Stephen Nathaniel Falken Iowa State University
Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1964 Some diffuse reflection problems in radiation aerodynamics Stephen Nathaniel Falken Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Aerospace Engineering Commons Recommended Citation Falken, Stephen Nathaniel, "Some diffuse reflection problems in radiation aerodynamics " (1964). Retrospective Theses and Dissertations. 3848. https://lib.dr.iastate.edu/rtd/3848 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. This dissertation has been 65-4604 microfilmed exactly as received FALiKEN, Stephen Nathaniel, 1937- SOME DIFFUSE REFLECTION PROBLEMS IN RADIATION AERODYNAMICS. Iowa State University of Science and Technology Ph.D., 1964 Engineering, aeronautical University Microfilms, Inc., Ann Arbor, Michigan SOME DIFFUSE REFLECTIOU PROBLEMS IN RADIATION AERODYNAMICS "by Stephen Nathaniel Falken A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF HîILOSOEHï Major Subjects: Aerospace Engineering Mathematics Approved: Signature was redacted for privacy. Cmrg^Vf Major Work Signature was redacted for privacy. Heads of Mgjor Departments Signature was redacted for privacy. De of Gradu^ e College Iowa State University Of Science and Technology Ames, loTfa 196k ii TABLE OF CONTENTS page DEDICATION iii I. LIST OF SYMBOLS 1 II. INTRODUCTION. 5 HI. GENERAL AERODYNAMIC FORCE ANALYSIS 11 IV. THE THEORY OF RADIATION AERODYNAMICS Ik A. -
Ap Physics 2 Summary Chapter 21 – Reflection and Refraction
AP PHYSICS 2 SUMMARY CHAPTER 21 – REFLECTION AND REFRACTION . Light sources and light rays Light Bulbs, candles, and the Sun are examples of extended sources that emit light. Light from such sources illuminates other objects, which reflect the light. We see an object because incident light reflects off of it and reaches our eyes. We represent the travel of light rays (drawn as lines and arrows). Each point of a shining object or a reflecting object send rays in all directions. Law of reflection When a ray strikes a smooth surface such as a mirror, the angle between the incident ray and the normal line perpendicular to the surface equals the angle between the reflected ray and the normal line (the angle of incidence equals the angle of reflection). This phenomenon is called specular reflection. Diffuse reflection If light is incident on an irregular surface, the incident light is reflected in many different directions. This phenomenon is called diffuse reflection. Refraction If the direction of travel of light changes as it moves from one medium to another, the light is said to refract (bend) as it moves between the media. Snell’s law Light going from a lower to a higher index of refraction will bend toward the normal, but going from a higher to a lower index of refraction it will bend away from the normal. Total internal reflection If light tries to move from a more optically dense medium 1 of refractive index n1 into a less optically dense medium 2 of refractive index n2 (n1>n2), the refracted light in medium 2 bends away from the normal line. -
Method for Measuring Solar Reflectance of Retroreflective Materials Using Emitting-Receiving Optical Fiber
Method for Measuring Solar Reflectance of Retroreflective Materials Using Emitting-Receiving Optical Fiber HiroyukiIyota*, HidekiSakai, Kazuo Emura, orio Igawa, Hideya Shimada and obuya ishimura, Osaka City University Osaka, Japan *Corresponding author email: [email protected] ABSTRACT The heat generated by reflected sunlight from buildings to surrounding structures or pedestrians can be reduced by using retroreflective materials as building exteriors. However, it is very difficult to evaluate the solar reflective performance of retroreflective materials because retroreflective lightcannotbe determined directly using the integrating sphere measurement. To solve this difficulty, we proposed a simple method for retroreflectance measurementthatcan be used practically. A prototype of a specialapparatus was manufactured; this apparatus contains an emitting-receiving optical fiber and spectrometers for both the visible and the infrared bands. The retroreflectances of several types of retroreflective materials are measured using this apparatus. The measured values correlate well with the retroreflectances obtained by an accurate (but tedious) measurement. The characteristics of several types of retroreflective sheets are investigated. Introduction Among the various reflective characteristics, retroreflective materials as shown in Fig.1(c) have been widely used in road signs or work clothes to improve nighttime visibility. Retroreflection was given by some mechanisms:prisms, glass beads, and so on. The reflective performance has been evaluated from the viewpointof these usages only. On the other hand, we have shown thatretroreflective materials reduce the heatgenerated by reflected sunlight(Sakai, in submission). The use of such materials on building exteriors may help reduce the urban heatisland effect. However, itis difficultto evaluate the solar reflective performance of retroreflective materials because retroreflectance cannot be determined using Figure 1. -
Directx ® Ray Tracing
DIRECTX® RAYTRACING 1.1 RYS SOMMEFELDT INTRO • DirectX® Raytracing 1.1 in DirectX® 12 Ultimate • AMD RDNA™ 2 PC performance recommendations AMD PUBLIC | DirectX® 12 Ultimate: DirectX Ray Tracing 1.1 | November 2020 2 WHAT IS DXR 1.1? • Adds inline raytracing • More direct control over raytracing workload scheduling • Allows raytracing from all shader stages • Particularly well suited to solving secondary visibility problems AMD PUBLIC | DirectX® 12 Ultimate: DirectX Ray Tracing 1.1 | November 2020 3 NEW RAY ACCELERATOR AMD PUBLIC | DirectX® 12 Ultimate: DirectX Ray Tracing 1.1 | November 2020 4 DXR 1.1 BEST PRACTICES • Trace as few rays as possible to achieve the right level of quality • Content and scene dependent techniques work best • Positive results when driving your raytracing system from a scene classifier • 1 ray per pixel can generate high quality results • Especially when combined with techniques and high quality denoising systems • Lets you judiciously spend your ray tracing budget right where it will pay off AMD PUBLIC | DirectX® 12 Ultimate: DirectX Ray Tracing 1.1 | November 2020 5 USING DXR 1.1 TO TRACE RAYS • DXR 1.1 lets you call TraceRay() from any shader stage • Best performance is found when you use it in compute shaders, dispatched on a compute queue • Matches existing asynchronous compute techniques you’re already familiar with • Always have just 1 active RayQuery object in scope at any time AMD PUBLIC | DirectX® 12 Ultimate: DirectX Ray Tracing 1.1 | November 2020 6 RESOURCE BALANCING • Part of our ray tracing system -
Visualization Tools and Trends a Resource Tour the Obligatory Disclaimer
Visualization Tools and Trends A resource tour The obligatory disclaimer This presentation is provided as part of a discussion on transportation visualization resources. The Atlanta Regional Commission (ARC) does not endorse nor profit, in whole or in part, from any product or service offered or promoted by any of the commercial interests whose products appear herein. No funding or sponsorship, in whole or in part, has been provided in return for displaying these products. The products are listed herein at the sole discretion of the presenter and are principally oriented toward transportation practitioners as well as graphics and media professionals. The ARC disclaims and waives any responsibility, in whole or in part, for any products, services or merchandise offered by the aforementioned commercial interests or any of their associated parties or entities. You should evaluate your own individual requirements against available resources when establishing your own preferred methods of visualization. What is Visualization • As described on Wikipedia • Illustration • Information Graphics – visual representations of information data or knowledge • Mental Image – imagination • Spatial Visualization – ability to mentally manipulate 2dimensional and 3dimensional figures • Computer Graphics • Interactive Imaging • Music visual IEEE on Visualization “Traditionally the tool of the statistician and engineer, information visualization has increasingly become a powerful new medium for artists and designers as well. Owing in part to the mainstreaming -
Geforce ® RTX 2070 Overclocked Dual
GAMING GeForce RTX™ 2O7O 8GB XLR8 Gaming Overclocked Edition Up to 6X Faster Performance Real-Time Ray Tracing in Games Latest AI Enhanced Graphics Experience 6X the performance of previous-generation GeForce RTX™ 2070 is light years ahead of other cards, delivering Powered by NVIDIA Turing, GeForce™ RTX 2070 brings the graphics cards combined with maximum power efficiency. truly unique real-time ray-tracing technologies for cutting-edge, power of AI to games. hyper-realistic graphics. GRAPHICS REINVENTED PRODUCT SPECIFICATIONS ® The powerful new GeForce® RTX 2070 takes advantage of the cutting- NVIDIA CUDA Cores 2304 edge NVIDIA Turing™ architecture to immerse you in incredible realism Clock Speed 1410 MHz and performance in the latest games. The future of gaming starts here. Boost Speed 1710 MHz GeForce® RTX graphics cards are powered by the Turing GPU Memory Speed (Gbps) 14 architecture and the all-new RTX platform. This gives you up to 6x the Memory Size 8GB GDDR6 performance of previous-generation graphics cards and brings the Memory Interface 256-bit power of real-time ray tracing and AI to your favorite games. Memory Bandwidth (Gbps) 448 When it comes to next-gen gaming, it’s all about realism. GeForce RTX TDP 185 W>5 2070 is light years ahead of other cards, delivering truly unique real- NVLink Not Supported time ray-tracing technologies for cutting-edge, hyper-realistic graphics. Outputs DisplayPort 1.4 (x2), HDMI 2.0b, USB Type-C Multi-Screen Yes Resolution 7680 x 4320 @60Hz (Digital)>1 KEY FEATURES SYSTEM REQUIREMENTS Power -
Reflection Measurements in IR Spectroscopy Author: Richard Spragg Perkinelmer, Inc
TECHNICAL NOTE Reflection Measurements in IR Spectroscopy Author: Richard Spragg PerkinElmer, Inc. Seer Green, UK Reflection spectra Most materials absorb infrared radiation very strongly. As a result samples have to be prepared as thin films or diluted in non- absorbing matrices in order to measure their spectra in transmission. There is no such limitation on measuring spectra by reflection, so that this is a more versatile way to obtain spectroscopic information. However reflection spectra often look quite different from transmission spectra of the same material. Here we look at the nature of reflection spectra and see when they are likely to provide useful information. This discussion considers only methods for obtaining so-called external reflection spectra not ATR techniques. The nature of reflection spectra The absorption spectrum can be calculated from the measured reflection spectrum by a mathematical operation called the Kramers-Kronig transformation. This is provided in most data manipulation packages used with FTIR spectrometers. Below is a comparison between the absorption spectrum of polymethylmethacrylate obtained by Kramers-Kronig transformation of the reflection spectrum and the transmission spectrum of a thin film. Figure 1. Reflection and transmission at a plane surface Reflection takes place at surfaces. When radiation strikes a surface it may be reflected, transmitted or absorbed. The relative amounts of reflection and transmission are determined by the refractive indices of the two media and the angle of incidence. In the common case of radiation in air striking the surface of a non-absorbing medium with refractive index n at normal incidence the reflection is given by (n-1)2/(n+1)2. -
Tracepro's Accurate LED Source Modeling Improves the Performance of Optical Design Simulations
TECHNICAL ARTICLE March, 2015 TracePro’s accurate LED source modeling improves the performance of optical design simulations. Modern optical modeling programs allow product design engineers to create, analyze, and optimize LED sources and LED optical systems as a virtual prototype prior to manufacturing the actual product. The precision of these virtual models depends on accurately representing the components that make up the model, including the light source. This paper discusses the physics behind light source modeling, source modeling options in TracePro, selection of the best modeling method, comparing modeled vs measured results, and source model reporting. Ray Tracing Physics and Source Representation In TracePro and other ray tracing programs, LED sources are represented as a series of individual rays, each with attributes of wavelength, luminous flux, and direction. To obtain the most accurate results, sources are typically represented using millions of individual rays. Source models range from simple (e.g. point source) to complex (e.g. 3D model) and can involve complex interactions completely within the source model. For example, a light source with integrated TIR lens can effectively be represented as a “source” in TracePro. However, sources are usually integrated with other components to represent the complete optical system. We will discuss ray tracing in this context. Ray tracing engines, in their simplest form, employ Snell’s Law and the Law of Reflection to determine the path and characteristics of each individual ray as it passes through the optical system. Figure 1 illustrates a simple optical system with reflection and refraction. Figure 1 – Simple ray trace with refraction and reflection TracePro’s sophisticated ray tracing engine incorporates specular transmission and reflection, scattered transmission and reflection, absorption, bulk scattering, polarization, fluorescence, diffraction, and gradient index properties. -
Ray-Tracing Procedural Displacement Shaders
Ray-tracing Procedural Displacement Shaders Wolfgang Heidrich and Hans-Peter Seidel Computer Graphics Group University of Erlangen fheidrich,[email protected] Abstract displacement shaders are resolution independent and Displacement maps and procedural displacement storage efficient. shaders are a widely used approach of specifying geo- metric detail and increasing the visual complexity of a scene. While it is relatively straightforward to handle displacement shaders in pipeline based rendering systems such as the Reyes-architecture, it is much harder to efficiently integrate displacement-mapped surfaces in ray-tracers. Many commercial ray-tracers tessellate the surface into a multitude of small trian- Figure 1: A simple displacement shader showing a gles. This introduces a series of problems such as wave function with exponential decay. The underly- excessive memory consumption and possibly unde- ing geometry used for this image is a planar polygon. tected surface detail. In this paper we describe a novel way of ray-tracing Unfortunately, because displacement shaders mod- procedural displacement shaders directly, that is, ify the geometry, their use in many rendering systems without introducing intermediate geometry. Affine is limited. Since ray-tracers cannot handle proce- arithmetic is used to compute bounding boxes for dural displacements directly, many commercial ray- the shader over any range in the parameter domain. tracing systems, such as Alias [1], tessellate geomet- The method is comparable to the direct ray-tracing ric objects with displacement shaders into a mul- of B´ezier surfaces and implicit surfaces using B´ezier titude of small triangles. Unlike in pipeline-based clipping and interval methods, respectively. renderers, such as the Reyes-architecture [17], these Keywords: ray-tracing, displacement-mapping, pro- triangles have to be kept around, and cannot be ren- cedural shaders, affine arithmetic dered independently. -
FTIR Reflection Techniques
FT-IR Reflection Techniques Vladimír Setnička Overview – Main Principles of Reflection Techniques Internal Reflection External Reflection Summary Differences Between Transmission and Reflection FT-IR Techniques Transmission: • Excellent for solids, liquids and gases • The reference method for quantitative analysis • Sample preparation can be difficult Reflection: • Collect light reflected from an interface air/sample, solid/sample, liquid/sample • Analyze liquids, solids, gels or coatings • Minimal sample preparation • Convenient for qualitative analysis, frequently used for quantitative analysis FT-IR Reflection Techniques Internal Reflection Spectroscopy: Attenuated Total Reflection (ATR) External Reflection Spectroscopy: Specular Reflection (smooth surfaces) Combination of Internal and External Reflection: Diffuse Reflection (DRIFTs) (rough surfaces) FT-IR Reflection Techniques • Infrared beam reflects from a interface via total internal reflectance • Sample must be in optical contact with the crystal • Collected information is from the surface • Solids and powders, diluted in a IR transparent matrix if needed • Information provided is from the bulk matrix • Sample must be reflective or on a reflective surface • Information provided is from the thin layers Attenuated Total Reflection (ATR) - introduced in the 1960s, now widely used - light introduced into a suitable prism at an angle exceeding the critical angle for internal reflection an evanescent wave at the reflecting surface • sample in close contact Single Bounce ATR with IRE