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Upcoming Deadlines Homework #12 – Lighting a Scene in Maya Due Wednesday, May 5 th (This Wednesday) 20 points (10 points if late) Homework #13 – Creating.

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Presentation on theme: "Upcoming Deadlines Homework #12 – Lighting a Scene in Maya Due Wednesday, May 5 th (This Wednesday) 20 points (10 points if late) Homework #13 – Creating."— Presentation transcript:

1 Upcoming Deadlines Homework #12 – Lighting a Scene in Maya Due Wednesday, May 5 th (This Wednesday) 20 points (10 points if late) Homework #13 – Creating Stereoscopic 3D Images Due Monday, April 17 th (Last day of classes) 20 points (10 points if late) There are no more furlough days for this class this semester. For full schedule, visit course website: ArtPhysics123.pbworks.com Pick up a clicker, find the right channel, and enter Student ID

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

3 Homework #12 Created by Candace Downey 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 from the dark background. Note: Sharp edges won’t pick up rim light in Maya.

4 Homework #12 Created by Candace Downey Render the three scenes, save each image, and upload them to your blog. Due by 8am on Wed., May 5 th 20 points (if late, 10) All Assignments and Extra Credit must be turned in by 5pm on Wednesday, May 19 th (same day as our final exam)

5 Activating your Clicker * Turn on your clicker. * Enter the channel number or letter for joining this class. Hit Enter/Send key. * Clicker should read AP123S258 * 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.

6 Survey Question How would you describe your experience using AutoDesk Maya? A)It’s a lot of fun to use B)Difficult to use but worth it C)Don’t like Maya all that much D)It’s a living Hell E)Haven’t used Maya

7 Review Question The fuzzy edge of a cast shadow is called the __________. A)Umbra B)Penumbra C)Form shadow D)Umber E)Castaway

8 Review Question B) Penumbra Notice how the cast shadow of Ellie’s arm is sharp while the shadows of the leaves of the tree on their faces are fuzzy. The farther the object is from the light, the wider the penumbra.

9 Inconsistent Shadows This fake cutting that circulated during the 2004 Presidential primaries combined a photo of John Kerry was taken 1971 with one of Jane Fonda taken in 1972. The form shadows on their clothes are clearly inconsistent.

10 Review Question In three point lighting, the third light shining from behind to distinguish the foreground objects from the dark background. This is called the _______. Three Point Lighting A)Key Light B)Fill Light C)Rim Light D)High Light E) Edge Light

11 Review Question Rim Key+ Fill+ Rim C) Rim Light From Casablanca (1942) The rim light is sometimes called the “back light” or the “kicker.” Because it’s often used to accent a person’s hair it’s also called the “hair light” or the “shoulder light.”

12 Review Question The intensity of light shining on a surface depends: A)Only on the distance between the light source and the surface. B)Only on the angle between the light source and the surface. C)On both the distance and the angle.

13 Review Question 7 light rays hit surface 5 light rays hit surface C) On both the distance and the angle. In both cases the light rays are spread over a larger area when the distance or the angle increases. Distance Angle

14 Optics & Lighting Part II: Reflection

15 Reflection and Shaders What makes wood look like wood and metal look like metal? It’s not just the color of a surface that indicates the material but also how it reflects light. In computer graphics, how light reflects from a surface is determined by the shader assigned to that surface.

16 Specular and Diffuse Reflection Reflection from most surfaces is diffuse, with incoming light scattered in all directions. Reflection from mirror surfaces is specular, with light reflecting in one direction. Mirror Diffuse reflection Specular reflection

17 Law of Specular Reflection Angle of incidence equals angle of reflection SPECULAR REFLECTION

18 Demo: Blackboard Optics Special blackboard has mounted light source and mirrors. Light Source Mirror Demonstrates the Law of Reflection Incident Reflected

19 Ray Tracing Light ray from point A is reflected at point B and arrives at point B. Notice the relationship between point B (where the ray is reflected to) and point B’ (where the ray would go if the mirror wasn’t there).

20 Demo: Who Do You See? A B C D E MIRROR Which person in the front row sees the guy with the hat in the mirror?

21 A B C D E Demo: Who Do You See? Diffuse light MIRROR Person A sees the guy with the hat when looking in the mirror. The converse is also true: Person E sees Person A in the mirror.

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

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

24 Sunrise/Sunset on the Ocean Instead of a single highlight we see a long “street” of light on the ocean at sunset. We are seeing many highlights from many random points on the wavy surface where the angle is just right.

25 Moonrise Illusion http://antwrp.gsfc.nasa.gov/apod/ap020130.html Is the Moon larger when near the horizon? No, the Moon is very nearly the same size no matter its location on the sky. In this time-lapse sequence, the Moon was re-imaged every 2.5 minutes, with the last exposure of longer duration to show the panorama of Seattle. The illusion occurs because foreground objects make a horizon Moon seem to be farther in the distance. The mind interprets more distant objects as wider; furthermore the distance illusion may make the eye focus differently.

26 Diffuse Surface is Not a Mirror Light rays diffusely scatter in every direction from every spot on the surface. See a light ray from the top of your head reflected from this spot. Also see light ray from the tip of your nose reflected from this spot. Look at this spot on a diffuse surface

27 Lambert Diffuse Reflection The apparent brightness of a Lambert surface is the same regardless of the observer's angle of view. This is typical of matte surfaces, such as paper and cloth. In computer graphics, Lambertian reflection is often used as a model for diffuse reflection. Rotating the view or scaling the object doesn’t change the apparent brightness of its surface. Key + Fill Key only

28 Directional Light on Diffuse Surface All points of a Lambert diffuse surface look equally bright under directional light.

29 No Highlight for Diffuse Surface Lamp No highlight on a Lambert diffuse surface but a gradual gradient due to angle and distance from lamp. This end is brighter because it’s closer to the lamp and because surface faces head-on.

30 Phong Reflection Phong reflection is a surface model combining the diffuse reflection of rough surfaces with the specular reflection of shiny surfaces. Shiny surfaces have small intense specular highlights, while dull surfaces have large highlights that fall off more gradually. The model also has an ambient term to account for the fill lighting.

31 Other Maya Shaders Blinn - Surfaces highlights are similar to Phong but with soft-tinted highlights as on metallic surfaces. Phong E - A faster rendering version of Phong that yields somewhat softer highlights. Anisotropic – Stretches highlights and rotates them based on the viewer's position; ideal for materials such as hair, feathers, brushed metal, and satin. Shading Map - Creates a "cel" look to mimic traditional, hand-drawn animation. Layered - Combine several shaders to create a more complex material.

32 Raytracing & Flat Mirrors Tracing light rays from original, to mirror, to eye allows us to construct image. Original Mirror HAIR NOSE TIE Image

33 Demo: Pocket Mirror See full image of your head in a plane mirror that’s half the size of your head.

34 Original Image Demo: Pocket Mirror See full image of your head in a plane mirror that’s half the size of your head. Mirror

35 Image in the Convex Mirror Jan van Eyck, Arnolfini Portrait, 1434 Convex mirror appears in this famous painting.

36 Mirror Reflections in Perspective Mirror reflection of this bird is almost an upside- down duplicate. In general, the reflection is not such a duplicate due to visual perspective.

37 Mirrors and Perspective Viewer’s Eye Level This image has consistent perspective so the image appears the right distance inside the mirror.

38 Mirrors and Perspective This image has inconsistent perspective; the image appears too close inside the mirror. Viewer’s Eye Level?

39 Image in the Mirror Edouard Manet, A Bar at the Folies-Bergere, 1882 Alfred Stevens, La Parisienne japonaise, c.1873 Gerard ter Borch, Woman at a Mirror, c.1650 Which work of art has a correct reflection? Incorrect Correct

40 Image in the Mirror Utamaro, Woman Powdering Her Neck Velazquez, Venus at her Mirror Helmut Newton, Bergstrom over Paris Which work of art has a correct reflection? Incorrect Correct

41 Non-Flat Mirrors Image in a curved mirror is distorted from original. Determine image location and size by ray tracing

42 Demo: Convex Mirrors MC Escher Hand with Reflecting Sphere Mirrored surface on a sphere or similar rounded shape. Image is smaller & closer.

43 Demo: Blackboard Convex Mirror Can use optics blackboard to trace diverging rays from convex mirror. Law of reflection still holds but mirror surface is curved.

44 Ray Tracing for Convex Mirror Image in convex mirror is smaller and closer. Original Image Mirror Although the image is closer, because it’s also smaller our brain tends to think it is farther away (since things look smaller as they get further away).

45 Demo: Concave Mirrors Mirror is on the inner curved surface of sphere or similar rounded shape. Image size and location depends on object’s distance from the mirror. Telescope

46 Demo: Blackboard Concave Mirror Use optics blackboard to trace convergence of rays from concave mirror. Notice that rays focus to a point (the focal point) then diverge, as with convex mirror. Focal Point

47 Ray Tracing for Concave Mirror Image in concave mirror is larger when original is close to the mirror. Original Image Mirror

48 Image Ray Tracing for Concave Mirror Original Mirror Image in a concave mirror is inverted if the original is far away from the mirror. Image is formed in front of the mirror!

49 3-Oct-15 Transparent, Reflecting Surfaces Water and glass are transparent but reflect some of the light striking their surface. Can see inside the cab through the right window. Strong reflection of the sun on the left window. Can see some of the riverbed through the water surface.

50 One Way Mirror One way mirror can be just a clear glass window. Bright Room Dark Room Discussion Room (Bright) Observation Room (Dark) GLASS Reflected light from bright room masks transmitted light from the darkened observation room

51 Reflection Coefficient The percentage of light that reflects from the surface of a transparent material is the reflection coefficient. Small angle Large angle Weak Reflection Strong Reflection Reflection coefficient depends on the material but also on the angle that the light hits the surface.

52 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.

53 Next Lecture Lighting Part III Scattering & Refraction Homework #12 (Lighting a Scene in Maya) Due this Wednesday Please turn off and return the clickers!


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