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Transcript of Upcoming Deadlines
Upcoming DeadlinesSecond Term PaperWednesday, November 25th (This Wednesday; no class that day)
Homework 11 (Building a scene in Maya)Monday, November 30th (Monday after Thanksgiving)
Homework 12 (Lighting a scene in Maya)Monday, December 7th (Last day of class)
For full schedule, visit course website:ArtPhysics123.pbworks.com
Homework AssignmentUsing Autodesk Maya create a scene consisting of a floor, a single wall in the background, and some objects in the foreground in the form of the initials of your name. Created by Candace DowneyRender the scene, save the image, and upload it to your blog.
Due by 8am on Monday, November 30th.20 points (if late, 10)
Final ExamFinal Exam will have of 10 short essay questions on material covered in lecture.Final exam counts for 50 points.
* What is the difference between stride and gait? How do they affect the walking speed?
* Describe how a scene would be lit using three point lighting.
Final ExamFinal exam is scheduled for:
Wednesday, December 16thIn this room from 12151430
You may take the final early on:
Wednesday, December 9thIn this room from 15001700
Special Campus EventAnimation Show of ShowsDecember 7th (Monday)At 7:30 PMMorris Dailey Auditoriumin Tower HallFREE
Optics & LightingPart II: Bending & Scattering
Global IlluminationNotice focusing of light through glass sphereWithout GIWith GIAdvanced computer graphics uses global illumination algorithms to compute a more physically realistic rendering of a scene.
CausticsCaustics are the bright concentrations of light caused by the focusing of that light when passing through a transparent object.Caustics also create shadow patterns, such as the bright and dark pattern in a swimming pool, due to the deflection of the light.
RefractionLight rays bend (refract) passing from water to air, making objects appear to be shallower and closer to the observer.ImageActualImageActualObserver sees image
Law of RefractionLight passing from one material to another is refracted by an angle that depends on the optical density of each material.
Angle is smaller in the denser material.
Demo: Refraction thru a BlockLight is refracted entering the block and refracted back on leaving the block.
Optical DensityAirWaterAirGlassAirDiamondn = 1.3n = 1.0n = 1.5n = 1.0n = 2.4n = 1.0Optical density is given by the index of refraction, n.
The larger the difference between the indices at an interface, the larger the angle of refraction for light rays crossing the interface.
Demo: InvisibilityMineral oil and glass have nearly the same index of refraction A glass rod is nearly invisible in a beaker of mineral oil.A diamond, however, is easily seen.
Refraction in a WedgeWhich path does light ray take after entering the glass wedge?
Path APath BPath CABCWEDGE
Path BThe angle always bends towards the perpendicular going from air to glass.Notice that it bends away from the perpendicular going back out of the glass.ABCWEDGERefraction in a Wedge
MiragesMirages are caused by the refraction of air because hot air has lower optical density than cold air. Hot AirCool Air
Total Internal ReflectionWhen refraction angle exceeds 90 the light does not cross the surface.RefractedReflectedReflected
Demo: Total Internal ReflectionJust below critical anglePast the critical angle all the light is internally reflected.
Demo: Total Internal ReflectionPrism demonstrates total internal reflection if the angle of incidence is large enough.No light escapes to this sideNo light escapes to this sideNo light escapes to this side
Looking up UnderwaterTry this when youre in the pool or the ocean next summer.Looking straight up you see the sky but outside the 96 cone surface is like a mirror
Natural Lighting UnderwaterDue to total internal refraction sunlight never enters the water at more than about a 45 degree angle.Image seen underwaterSun
Fiber OpticsTotal internal reflection causes light to reflect inside a solid glass tube.
LensesConcave lens shrinks its imageConvex lens magnifies its imageCurvature of a lens surface produces a continuous, variable angular refraction.
Demo: Concave LensesCurved surface of a concave lens causes light rays to diverge, dispersing the light and shrinking any images.
Demo: Convex LensesCurved surface of a convex lens causes light rays to converge, focusing the light and possibly magnifying images.
Demo: Real Image of Convex LensImage formed by convex lens can be observed on a screen.
Pinhole CameraSmall pinhole allows only small amount of light in, blocking overlapping diffuse rays and forming image inside the camera.
Demo: Pinhole LensMake a small pinhole in a piece of cardboard. Youll find that you can focus better when looking through the pinhole. ETGWRPOCVMXSRYUQBNEHDThis works best if you remove any corrective lenses, such as contacts and eyeglasses.
Camera ObscuraThe camera obscura (room darkened) dates to ancient times; it was first detailed in the writings of Leonardo da Vinci.A room is completely sealed from light except for a coin-sized hole in one wall. An image of the outside world appears projected, upside down and reversed right-to-left, onto a wall opposite the opening. Diffuse light
Giant CameraCamera obscura with a projecting mirror.Next to the Cliff House, San FranciscoMirrorMirror
Johannes Vermeer (1632-75)The Music LessonCommon elements in his paintings and ray tracing analysis suggest that this great Dutch artist may have built a camera obscura in his studio.
Camera LensUsing a lens allows for more light to be focused on the camera screen or film.No image (Diffuse)Camera obscuraCamera with lens
The Lens of the EyeImage is formed upside-down on the retina of the eye.The eyes lens changes shape to focus the image onto light sensitive cells of retina.
Visual AcuityIf eyes lens is unable to form image on the retina, an object will appear out of focus.Myopia Hyperopic
EyeglassesLenses of eyeglasses restore visual acuity by combining with the eyes lens to form focused image onto retina.Eyeglasses began to appear in common use in the 13th century. They may have been invented in northern Italy but Marco Polo reports them in China as early as 1275.
Detail of portrait of Hugh de Provence, Tomasso da Modena, 1352 Pinhole glasses
AstigmatismAstigmatism due to eyes lens being elliptical, which causes the focus in the vertical to differ from horizontal.Vertical focusAstigmatism may be corrected using a cylindrical lens.In this example, the lens focuses in the horizontal only since vertical is already in focus.
Spectrum of Visible Light
Demo: Infrared LightDigital cameras, such as in cell phones, are sensitive to infrared light, such as from a remote control or any hot object.
Separating ColorsBlue wavelength of light refracts slightly more than the red, creating rainbows.Glass PrismWaterDroplet
RainbowsRainbows are formed by refraction from many, many raindrops. The red part is always above the blue part.
Diamond CutsDiamonds are cut so as to create a beautiful jewelry by taking advantage of total internal reflection and high color dispersion (prism effect).
Atmospheric PerspectiveObjects in the distance have a bluish, unsaturated color due to atmospheric scattering of blue light (same as blue sky).
Atmospheric Perspective Example
Perspective of ColorNot only did he make good use of what he called Perspective of Color but Leonardo also correctly predicted that this is why the sky is blue.The Virgin of the Rocks, Leonardo, 1482
Light ScatteringMie ScatteringDirect scattering by suspended particles, such as dust, fog, etc.Also called Rayleigh-Brillouin Scattering*Rayleigh Scattering*Refraction by random variations in a transparent medium.For both types of scattering blue light tends to scatter more strongly than red light.
Mie Scattering Examples
Volumetric LightingVolumetric lighting is used to create the volume of scattered light, usually due to Mie scattering.
Next LectureSeeing ColorNo class this Wednesday butSecond Term Paper due on WednesdayPlease return the clickers!
*****************************There is a large camera obscura located next to San Franciscos Cliff House*********************