Upcoming Deadlines Pick up a clicker find the

Upcoming Deadlines Pick up a clicker, find the right channel, and enter Student ID Homework #12 – Lighting a Scene in Maya Due Wednesday, December 1 st (Week from today) 20 points (10 points if late) Homework #13 – Creating Stereoscopic 3 D Images Due Wednesday, December 8 th (In two weeks) 20 points (10 points if late) For full schedule, visit course website: Art. Physics 123. pbworks. com

Homework #12 Light the scene created in your previous homework assignment using one, two, and three-point lighting. One-point Lighting: Light the scene with a single bright spot light on the left side; this is your key light. Created by Candace Downey

Homework #12 Two-point Lighting: Add a dim fill light on the right side to soften the shadows created by the key light. Three-point Lighting: Add a bright rim light behind the letters to accentuate their edges Created by Candace Downey from the dark background.

Homework #12 Render the three scenes, save each image, and upload them to your blog. Due by 8 am on Wed. , December 1 st 20 points (if late, 10) All Assignments and Extra Credit must be turned in by 5 pm on Tuesday, Candaceexam) Downey December 14 th (day of Created the by final

Final Exam will have of 10 short essay questions on material covered in lecture. Final exam counts for 50 points. See course website for copy of last semester’s final exam. You may bring one page of notes doublesided (or two pages single-sided) to the exam.

Activating your Clicker * Turn on your clicker. * Enter the channel number or letter for joining this class. Hit Enter/Send key. * Clicker should read AP 123 GF 10 * Type in your student ID; hit Enter/Send. Clicker is now ready to use; leave it on. Hit any key to wake the clicker from sleep mode.

Survey Question How much time did this week’s homework (Building a Scene in Maya) take you to complete? A) B) C) D) E) Less than an hour Between one and two hours Between 2 and 4 hours Over four hours Didn’t finish that assignment

Finding the Highlight Lamp Where does Albert see the highlight reflected off this metal block? A B D: None of these C Albert

Finding the Highlight Lamp Albert C Light rays from point C reach Albert.

Review Question Matte surfaces, such as paper and cloth, are typically rendered in computer graphics using which shading model? A) Phong B) Blinn C) Thong D) Lambert E) Mambo Key only Key + Fill

Review Question D) Lambert Johann Heinrich Lambert (1728– 1777) A Lambert surface scatters light diffusely so under directional light it looks equally bright from all angles.

Review Question What is the shape of the mirrors in these photos? A) B) Concave Mirror Convex Mirror

Review Question A) Concave Mirror Original Mirror Image

Review Question The dependence of reflection on angle is called the ______ effect. Looking straight down into a pool of water we see little reflection of the sky. Looking at the water at a large angle we see a strong reflection of the sky.

Review Question The dependence of reflection on angle is called the ______ effect. A) Reflex D) Fresnel Small angle B) Reflux C) Rephase E) What-The-Flux Large angle Weak Reflection Strong Reflection

Fresnel Effect The dependence of reflection on angle is called the Fresnel effect. Looking straight down into a pool of water we see little reflection of the sky. Looking at the water at a large angle we see a strong reflection of the sky.

Optics & Lighting Part III: Bending & Scattering

Global Illumination Advanced computer graphics uses global illumination algorithms to compute a more physically realistic rendering of a scene. Without GI With GI Notice focusing of light through glass sphere

Refraction Light rays bend (refract) passing from water to air, making objects appear to be shallower and closer to the observer. Observer sees image Image Actual

Reciprocity Light bends the same way whether it’s entering the water or coming out of the water. Laser This symmetry for light rays is called “reciprocity. ”

Law of Refraction Light 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 Block Light is refracted entering the block and refracted back on leaving the block.

Optical Density Optical density is given by the index of refraction, n. Air The larger the difference between the indices at an interface, the larger the angle of refraction for light rays crossing the interface. Air Water Glass Air Diamond n = 1. 0 n = 1. 3 n = 1. 0 n = 1. 5 n = 1. 0 n = 2. 4

Demo: Invisibility Mineral 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 Wedge Which path does light ray take after entering the glass wedge? A)Path A B) Path B C) Path C A B C WEDGE

Refraction in a Wedge Path B The 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. A B C WEDGE

Lenses Curvature of a lens surface produces a continuous, variable angular refraction. Concave lens shrinks its image Convex lens magnifies its image

Demo: Concave Lenses Curved surface of a concave lens causes light rays to diverge, dispersing the light and shrinking any images.

Demo: Convex Lenses Curved surface of a convex lens causes light rays to converge, focusing the light and possibly magnifying images.

Camera Lens Using a lens allows for light to be focused on a screen or camera film. No image (Diffuse) Camera with lens

Demo: Real Image of Convex Lens Image formed by convex lens can be observed on a screen.

Bokeh Effect (Lens Blur) Point lights expand into balls of light when the light source is out of focus (outside the depth of field). The term is from the Japanese word boke (暈け or ボケ), which means "blur" or "haze. "

Focusing and Shadows When refraction focuses light to create bright areas, it also removes light and creates shadowed areas. Dark Bright

Caustics Refraction caustics Caustics are the bright concentrations of light caused by the focusing of that light by refraction or Reflection caustics by reflection. Caustics also create shadow patterns, which visually accent the caustic’s brightness.

Total Internal Reflection When refraction angle exceeds 90º the light does not cross the surface. d e t c ra f e R fl Re Re fle ed t ec ct ed

Atmospheric Perspective Example

Demo: Total Internal Reflection Past the critical angle all the light is internally reflected. Just below critical angle

Demo: Total Internal Reflection Prism demonstrates total internal reflection if the angle of incidence is large enough. No light escapes to this side

Looking up Underwater Try this when you’re 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 Underwater Due to total internal refraction sunlight never enters the water at more than about a 45 degree angle. Image seen underwater Sun

Fiber Optics Total internal reflection causes light to reflect inside a solid glass tube.

Separating Colors Blue wavelength of light refracts slightly more than the red, creating rainbows. Water Droplet Glass Prism

Rainbows are formed by refraction from many, many raindrops. The red part is always above the blue part.

Double Rainbow Primary Secondary

Atmospheric Perspective Objects in the distance have a bluish, unsaturated color due to atmospheric scattering of blue light (same as blue sky).

“Perspective of Color” Not 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 Scattering Mie Scattering by particles, such as droplets of fog, of micron size. 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. Also called Rayleigh-Brillouin Scattering*

Mie Scattering Notice the shadows Particles in Mie scattering are often transparent or highly reflective.

Suspended Particles A dust storm is seen from the reflection off the suspended dust particles rather than true scattering. Mie scattering by water droplets in clouds. Reflection from suspended particles.

Rayleigh Scattering Sky is blue due to Rayleigh scattering of sunlight in the atmosphere. When sunlight passes through a very thick layer all the blue is scattered out and we’re left with yellowish red.

Underwater Perspective Water is transparent but absorbs red light about x 100 more than blue light. Objects in distance are bluish but saturated. Significant reflection by suspended particles. Particles are easily mixed in water due to buoyancy.

Volumetric Lighting Volumetric lighting is used to create the volume of scattered light, usually due to Mie scattering.

Call of Duty: Black Ops (2010) Atmospheric effects are important for creating the right look for this snow level in the game. http: //www. youtube. com/watch? v=l 7 PRTYn 3 ZMk

Next Lecture Seeing Color Happy Thanksgiving Please turn off and return the clickers!