Pick up a clicker, find the right channel, and enter Student ID Upcoming Deadlines Homework #12 –Cameras and Lights in Maya Due Tuesday, May 8th (Next week) 20 points (10 points if late) Homework #13 – Creating Stereoscopic 3D Images Due Tuesday, May 15th (Last day of classes) 20 points (10 points if late) For full schedule, visit course website: ArtPhysics123.pbworks.com
Homework #12 For this assignment you are given a photograph of a real object and you will try to match the camera and the lighting. Each person will have a choice of four photos; for the assignment match any one of these photos (for extra credit, do more than one). To find the photographs assigned to you, go to: http://tinyurl.com/6uom7kp
Homework #12 The Maya model for this "widget" object has been created for you and may be downloaded here: http://tinyurl.com/7zhsaf7 Open the object in Maya, create a surface for it to sit on, position the camera, add some lights, and adjust everything until your rendered Maya image looks as closely as possible to the photograph. Try to match any colors, for the object and the lights, as well as the details of the shadows (e.g., penumbra angles, ambient light, drop-off).
Homework #12 To finish, move the position of your camera to view the scene from another direction (suggest that you turn the camera roughly 45 degrees to either side). Render #1 Render #2
Homework #12 Finally, upload the photo you chose to use and the two Maya rendered images into a posting entitled "Recreating Cameras and Lights in Maya." Note that this is a new assignment this year so there are no examples from previous semesters; contact me if you have any questions. Due by 8am on Tuesday, May 8th 20 points (10 points if late)
Homework #12 Non-Maya Alternative: One of the four photographs is a pair of soup cans. Recreate the camera and lighting in that photograph as accurately as possible then take your own photos of the scene. Finish by taking a second photograph with the camera at about 45 degrees to either side of its original position. Upload both of your photographs as well as the photograph that you're matching. Note that it will not be easy to duplicate the lighting conditions using common house lamps; only do this alternative if you find it absolutely impossible to work with Maya.
Final Exam Final exam is on Tuesday, May 22nd from 1215 to 1430 in this classroom. Final Exam will have of 10 short essay questions on material covered in lecture. Final exam counts for 50 points. You may bring one page of notes double-sided (or two pages single-sided) to the exam.
Final Exam Visit the course website for more info on your final exam (including sample). Note that the final exam is optional. All Assignments and Extra Credit must be turned in by 5pm on May 22nd
Special Event PIXAR presentation on "Brave" in Washington Square Room 109 at 3:30pm today. Go immediately after class if you hope to get a seat!
Survey Question From which of these assignments did you learn the most: • Term papers • Homeworks using Tracker • Stop-motion animation homeworks • Homeworks using Maya • Reverse video reference
Review Question Which path does light ray take after entering the water? • Path A • Path B • Path C • Path D D A C B
Law of Refraction C) Path C Angle is smaller in the denser material. The light ray bends but does not cross the normal (line perpendicular to the surface)
Review Question What looks like a pool of water in this photo is actually a mirage image of the sky created due to the desert heat. • Mirages are produced by: • Refraction • Reflection • Scattering • Miracles • Myopia
Mirages A) Refraction Mirages are caused by the refraction of air because hot air has lower optical density than cold air. Cool Air Hot Air
Review Question Natural lighting underwater is primarily from overhead because sunlight cannot enter the water at more than about a 45 degree angle. True or False?
Total Internal Reflection True. For the same reason you can only see the sky from underwater when looking up at more than about a 45 degree angle. See sky Mirror
Elements of Optics Reflection Scattering Eye-Brain Light Source Refraction
DW Consulting Example Disco lights for Intel commercial
Basic Scattering Some sunlight is scattered, making the fog visible.
Scattering Out & Scattering In To this viewer, the fog has scattered out some of the light so the sun isn’t as bright To this viewer, the fog has scattered in some light so the fog is visible.
Scattering vs. Absorption Scattering is a deflection of the light. Absorption is an elimination of light. 40% 100% 50% 10% For example, if 40% of the light is scattered and 10% is absorbed then 50% directly reaches viewer.
Extinction Extinction defined as absorption plus scattering. 40% 100% 40% scattered10% absorbed 50% 10% 10% 100% 10% scattered40% absorbed 50% 40% Extinction is 50% in both cases.
Demo: Scattering vs. Absorption Beakers filled with water placed on overhead projector. Beaker has drop of white ink, the other has a drop of black ink. ? What is seen on the screen?
Demo: Scattering vs. Absorption Glass dishes filled with water placed on overhead projector. One dish has drop of milk, the other has a drop of black ink. Projected image has two dark spots. Black ink absorbs light. White ink scatters light.
Particle Sizes & Scattering Large Particles (Reflection/ Refraction) Tiny Particles (Rayleigh Scattering) Air Birds Cloud Small Particles (Mie Scattering)
Rayleigh Scattering Particle Sizes & Color Tiny Particles – Scatter blue light the most, red the least; white light scattered with a hue shift to blue. Gas fumes Fine smoke Particles smaller than wavelength of visible light. Air molecules
Rayleigh Scattering by Color Blue light: 440 nm Green light: 550 nm Red light: 660 nm For tiny particles (under 400 nm) scattering is strongest for blue light and weakest for red light. Scattering Strength Particle Size 0 200 nm 400 nm
Tyndall Scattering Tyndall scattering is very similar to Rayleigh scattering since both are the scattering of light (especially blue light) by very small particles. Blue iris Opalescent glass
Demo: Aerogel Opalescence Aerogel is ultralight, hard foam made from SuperGlue. Scattering makes aerogel look blue while the transmitted light is yellow. Flashlight shines white light on a piece of aerogel
Mie Scattering Particle Sizes & Color Small Particles – Scattering of hues varies with particle size, usually averaging out to white. White paint Milk Particles comparable to wavelength of visible light. Clouds
Mie Scattering by Color Blue light: 440 nm Green light: 550 nm Red light: 660 nm For small particles Mie scattering strength varies greatly with the particle size. Since particles tend to be a mix of sizes, all hues are scattered equally resulting in white. Scattering Strength Particle Size 400 nm 800 nm 1200 nm
Particle Sizes & Color Confetti Large Particles – Reflect light off the surface or, if transparent, refract and transmit light. Sand Particles much larger than the wavelength of visible light. Rain
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.
Volumetric Lighting Volumetric lighting is used to create the volume of scattered light, usually due to Mie scattering in dust or fog.
Scattering & Angle Direction of light scattering is not random. Forward Backward More light Less light
Mie Scattering & Angle Mie scattering is strongest in the forward and weakest backward directions. Fog
Mie Forward Scattering Sun Sun is behind the fog in this photo Fog Mie scattering from drier fog Drier Vent Camera
Mie Backward Scattering Sun is behind the camera in this photo Fog Camera Mie scattering from drier fog Drier Vent Sun
Mie scattering by fog mist Sun Rays Intensity of sun rays varies with the angle between sun and viewer. Notice that the light on the ground is bright even though the ray’s intensity appears to taper off along the sun ray. To camera To camera
Rayleigh Scattering & Angle Rayleigh scattering is strongest in the forward and backward directions. It is weakest to the sides (90 degrees). Gas fumes
Brightness of the Sky The darkest part of the sky tends to be about 90 degrees from the direction of the sun. Rayleigh scattering by air molecules From Sun
Single vs. Multiple Scattering Light rays may scatter multiple times, if the scattering medium is dense. Light Fog Heavy Fog
Demo: Scattering in a Fish Tank Single versus multiple scattering is nicely shown by shining a flashlight into an aquarium filled with clean water then adding more and more milk.
Single Scattering in a Fish Tank Single scattering produces a narrow beam of light. Flashlight Mie scattering by very dilute water/milk mix.
Single Scattering in a Fish Tank Intensity differences due to scattering angle (i.e., near the light we have more forward scattering). Flashlight To camera To camera
Multiple Scattering in a Fish Tank Multiple scattering produces a diffuse beam of light. Flashlight Hue shift from white (near flashlight) to orange-red on the opposite side.
Scattering in a Fish Tank With single scattering only particles in the direct beam are scattering the light. To camera With multiple scattering particles outside the beam are illuminated by light scattered from out of the beam. To camera