Upcoming Deadlines Pick up a clicker, find the right channel, and enter Student ID 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) 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

Photo

Homework #12 http://tinyurl.com/7zhsaf7 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).

Maya Render

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 Due by 8am on Tuesday, May 8th 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 will have of 10 short essay questions on material covered in lecture. Final exam counts for 50 points. See course website for copy of an example of a final exam from an earlier semester. You may bring one page of notes double-sided (or two pages single-sided) to the exam.

Final Exam Final exam is on Tuesday, May 22nd from 1215 to 1430 in this classroom. 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

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

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

Finding the Highlight C Lamp Albert 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? Phong Blinn Thong Lambert Mambo Key only Key + Fill

Lambert Reflection D) Lambert Lambert surface looks equally bright under different viewing angles. D) Lambert Lamp

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

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

Can you cast a shadow on a mirror? Challenge Question Can you cast a shadow on a mirror? Yes No

Shadows & Mirrors No No shadow of my arm on the mirror. Note: If mirror is dirty then shadow is seen on the dust

Optics & Lighting Part III: Refraction

Elements of Optics Reflection Scattering Eye-Brain Light Source Refraction

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 Image Actual Actual

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.

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.”

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. The larger the difference between the indices at an interface, the larger the angle of refraction for light rays crossing the interface. Air n = 1.0 n = 1.3 Water Air n = 1.0 n = 1.5 Glass Air n = 1.0 n = 2.4 Diamond

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.

Demo: Invisibility Pour oil on frosted glass plate; see through the glass

Removing scratches Waxing a surface doesn’t remove scratches, it just matches refraction.

Refraction in a Wedge Which path does light ray take after entering the glass wedge? Path A Path B Path C A B C WEDGE

Refraction in a Wedge Path B The angle always bends towards the perpendicular going from air to glass. A B C WEDGE

Refraction in a Wedge (2) Which path does light ray when it reaches the opposite side? Path A Path B Path C A B C WEDGE

Refraction in a Wedge (2) Path B Notice that it bends away from the perpendicular going back out of the glass. By reciprocity the path of the light ray is the same if we reverse the direction of the arrows. 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: Lenses Light rays converge or diverge by refraction passing through a lens. Concave lens Convex lens

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 by reflection. Reflection caustics Caustics also create shadow patterns, which visually accent the caustic’s brightness.

Focusing and Shadows Water is transparent yet the droplets cast shadows due to refraction.

Heat Shimmer and Mirages http://www.youtube.com/watch?v=9cdrLG9xx0Y

Mirages Mirages are caused by the refraction of air because hot air has lower optical density than cold air. Cool Air Hot Air

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

Image inversion An object located past the focal point is inverted by a convex lens.

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

Hooke’s Micrographia In 1665, Robert Hooke produced detailed illustrations using the newly discovered instrument: the microscope.

The Lens of the Eye The eye’s lens changes shape to focus the image onto light sensitive cells of retina. Image is formed upside-down on the retina of the eye.

Visual Acuity If eye’s lens is unable to form image on the retina, an object will appear out of focus. Myopia Hyperopic

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."

Astigmatism Astigmatism due to eye’s lens being elliptical, which causes the focus in the vertical to differ from horizontal. Vertical focus Astigmatism may be corrected using a cylindrical lens. In this example, the lens focuses in the horizontal only since vertical is already in focus.

Total Internal Reflection When refraction angle exceeds 90º the light does not cross the surface. Refracted Reflected Reflected

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 No light escapes to this side 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

Refraction in Aquariums Seeing around the side of log Mirror reflection of sculpture

Refraction in Aquariums Different views on front and side walls due to refraction Total internal reflection off side wall

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

Demo: Laser in Water Stream Total internal reflection causes light to reflect inside a stream of water. Laser

Next Lecture Scattering Homework #12 Recreating Cameras and Lights in Maya Due Tuesday, May 8th (Next week) Please turn off and return the clickers!