physically based rendering

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1. Physically-Based Rendering Theory and Practice Koray Hagen 2. The agenda Lighting and shading models with live demonstration Theoretical basis for PBR with live demonstration Q & A 3. Reality and simulation Three thousand years of research 4. A brief history 4th century B.C. Ancient Greeks incorrectly believe vision involves emanations from the eye to the object perceived. 5. A brief history 4th century B.C. Ancient Greeks incorrectly believe vision involves emanations from the eye to the object perceived. Euclid successfully describes the law of reflection using geometry. 6. A brief history 17th century A.D. Kepler, Snell, Fermat, and Descartes contribute to the law of refraction. 7. A brief history 17th century A.D. Kepler, Snell, Fermat, and Descartes contribute to the law of refraction. Newton observes dispersion,proving light is composed of component colors. 8. A brief history 19th century A.D. Fresnel discovers the laws that enable the intensity and polarization of reflected and refracted light to be calculated. 9. A brief history 19th century A.D. Fresnel discovers the laws that enable the intensity and polarization of reflected and refracted light to be calculated. Maxwell summarizes and extends all current empirical knowledge of optics and electromagnetism with a single set of equations. 10. A brief history 19th century A.D. Fresnel discovers the laws that enable the intensity and polarization of reflected and refracted light to be calculated. Maxwell summarizes and extends all current empirical knowledge of optics and electromagnetism with a single set of equations. Hertz discovers the photoelectric effect. 11. A brief history 20th century A.D. Planck discovers a universalconstant explainingthe relationship between the energy and frequency of an electromagnetic wave. 12. A brief history 20th century A.D. Planck discovers a universalconstant explainingthe relationship between the energy and frequency of an electromagnetic wave. Einstein explains the photoelectric effect based on streams of quantized energy packets. 13. A brief history 20th century A.D. Planck discovers a universalconstant explainingthe relationship between the energy and frequency of an electromagnetic wave. Einstein explains the photoelectric effect based on streams of quantized energy packets. Feynman makes large contributions to quantum field theory and quantum electrodynamics. 14. A brief history 21st century A.D. Jet Propulsion Laboratoryhires PhD graduateJim Blinn to work on computer graphics research and simulations for various space missions. 15. A brief history 21st century A.D. Jet Propulsion Laboratoryhires PhD graduateJim Blinn to work on computer graphics research and simulations for various space missions. These incredible visualizations were shown all over the world. 16. Our journey to physicallybased rendering begins here. 17. Lighting and shading models Research prior to physicallybased rendering 18. What is physically-based rendering? 19. What is physically-based rendering? Many things and it depends 20. What is physically-based rendering? Many things and it depends Must observe how it differs from other older rendering methods. 21. What is physically-based rendering? Many things and it depends Must observe how it differs from other older rendering methods. What makes PBR different is in how we reason about the behavior of light and surfaces in computer graphics. 22. What is physically-based rendering? Many things and it depends Must observe how it differs from other older rendering methods. What makes PBR different is in how we reason about the behavior of light and surfaces in computer graphics. By modeling physical phenomena rather than approximating observation, we can achieve more mathematically stable and photorealistic visual fidelity. 23. Some terminology Lighting model the behavior of interactions between materials and light sources. Normally attributed to be a topic in physics. 24. Some terminology Lighting model the behavior of interactions between materials and light sources. Normally attributed to be a topic in physics. Shading model the process of determining the color of a pixel. Normally attributed to be a topic in computer graphics. 25. Some terminology Diffusion and reflection also known as diffuse and specular reflection. 26. Some terminology Diffusion and reflection also known as diffuse and specular reflection. Describe the most basic separation of light and surface interactions. 27. Some terminology Diffusion and reflection also known as diffuse and specular reflection. Describe the most basic separation of light and surface interactions. Specular reflection is the behavior of light hitting a surfaceboundaryand perfectly reflecting off of it, much like how a mirror would behave. 28. Some terminology Diffusion and reflection also known as diffuse and specular reflection. Describe the most basic separation of light and surface interactions. Specular reflection is the behavior of light hitting a surfaceboundaryand perfectly reflecting off of it, much like how a mirror would behave.. Diffusion occurs when not all light reflects from the surface. Some will penetrate into the interior of the illuminated object. There it will either be absorbed by the material (usuallyconverting to heat) or scattered internally. 29. Some terminology Diffusion and reflection also known as diffuse and specular reflection. Describe the most basic separation of light and surface interactions. Specular reflection is the behavior of light hitting a surfaceboundaryand perfectly reflecting off of it, much like how a mirror would behave.. Diffusion occurs when not all light reflects from the surface. Some will penetrate into the interior of the illuminated object. There it will either be absorbed by the material (usuallyconverting to heat) or scattered internally. The absorption and scattering of diffuselight are often quite different for different wavelengths of light, which is what gives objects their color (e.g. if an object absorbs most light but scatters blue, it will appear blue). 30. How was light modeled in 1977? 31. Blinn-Phong Shading Model Every surfaceis made of some material and each material reflects light differently. 32. Blinn-Phong Shading Model Every surfaceis made of some material and each material reflects light differently. Think of how metal objects are shiny and wooden objects are matte. We need to have a way to specify material parameters that can control how a surfacereflects light. 33. Blinn-Phong Shading Model Every surfaceis made of some material and each material reflects light differently. Think of how metal objects are shiny and wooden objects are matte. We need to have a way to specify material parameters that can control how a surfacereflects light. Every surfacecan then be approximated with three reflectivity constants, and they control the intensity of the various reflections. ambient reflectivity specular reflectivity diffusereflectivity specular highlighting 34. Blinn-Phong Shading Model By sampling relevant spatial information from a three dimensional scene, the light intensity at point can be calculated. 35. Blinn-Phong Shading Model By sampling relevant spatial information from a three dimensional scene, the light intensity at point can be calculated. The normalvector to the surface The light vector from the surface The view vector 36. Blinn-Phong Shading Model By sampling relevant spatial information from a three dimensional scene, the light intensity at point can be calculated. The normalvector to the surface The light vector from the surface The view vector Lamberts Law states that the diffusion at a point is proportional to the cosine of the angle between the incoming light ray and the normal of the surface . 37. Blinn-Phong Shading Model Diffusion value Ld derived from Lamberts Law Ld = Kd * dot(N, L) * light source intensity Specular reflection value Ls Phong: Ls = Ks * exp(dot(R, V), a) * light source intensity Blinn: Ls = Ks * exp(dot(N, H), a) * light source intensity Ambient light value La La = Ka * ambient light intensity 38. Blinn-Phong Shading Model Diffusion value Ld derived from Lamberts Law Ld = Kd * dot(N, L) * light source intensity Specular reflection value Ls Phong: Ls = Ks * exp(dot(R, V), a) * light source intensity Blinn: Ls = Ks * exp(dot(N, H), a) * light source intensity Ambient light value = Light intensity at a pixel equals the sum of + + shadertoy example 39. Blinn-Phong is far from perfect Does not respect conversation of energy. As specular power is increased, more energy is lost from the system. 40. Blinn-Phong is far from perfect Does not respect conversation of energy. As specular power is increased, more energy is lost from the system. Isnt expressive enough to simulate more complex materials due to crude approximations of diffusion and reflective properties. 41. Blinn-Phong is far from perfect Does not respect conversation of energy. As specular power is increased, more energy is lost from the system. Isnt expressive enough to simulate more complex materials due to crude approximations of diffusion and reflective properties. Ambient lighting completely ignores diffusion properties of environment. 42. Blinn-Phong is far from perfect Does not respect conversation of energy. As specular power is increased, more energy is lost from the system. Isnt expressive enough to simulate more complex materials due to crude approximations of diffusion and reflective properties. Ambient lighting completely ignores diffusion properties of environment. Terrible workflow for artists, due to final visuals being dependent on physically incorrect tweaks o

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