NaimExplain

Provide an example of an artificial spatial cue. Why are these used? Answer: Enhance 3d scatter plots by dropping a line from each points, without those lines, only 2d judgement of spatial layer is possible. With those lines, we can estimate the points' 3D position.

Provide two examples of where perspective is intentionally distorted in 20th century art. Why might this be effective? The Disney Princess castle - Made to look much larger and further away than it is. This is done by using smaller bricks at the top of the tower, which progressively get larger. Also, the houses lining the street to the castle progressively get larger (We perceive things that are smaller as further away). This is useful in creating a sense of wonder for those visiting the park Julian Beever - Creates chalk drawings that look 3d by distorting the images he draws themselves, this again creates a sense of wonder when viewed from the correct perspective (has to be viewed from correct perspective)

How does one make a three-dimensional postcard? Answer: Lenticular images combine digitally interlaced printed or photographic image with rows of optical grade lenses. They focus light on different strips of the surface and magnifies whatever image is there. Viewing the image from different angles - by moving - creates the desired illusion.

Describe the relationship between 'shape from shading' and the position of the light source. Shape can be recovered from a single image by human visual system based on the shading information. To estimate the shape from a single image, some assumptions have to be made, e.g. constant albedo (surface color). This technique is very useful for reconstructing surfaces of planets from photographs acquired by spacecrafts. For example, the concave/convex ambiguity

Describe each system and provide at least one perceptual disadvantage for each of the following three-dimensional display methods: Chromadepth glasses have a ridged surface, made up of little prisms. Looking really closely reveals that you are looking through alot of little prisms. It bends light at different wavelengths to different extents. ADVANTAGES- cheap viewing equipment needed disadvantages, color is tied to depth. Red seems close, blue seems far

Describe each system and provide at least one perceptual disadvantage for each of the following three-dimensional display methods: Passive polarization 1. Two films taken at two different positions 2. Two films projected trough polarizers onto silver oxide screen 3. Audience must wear polarized glasses Advantages- large audiences, motion, color disadvantages- expensive silver oxide screen, ghosting, polarizers reduce intensity

Describe each system and provide at least one perceptual disadvantage for each of the following three-dimensional display methods: Autostereogram The trick is to display slightly different images to the two eyes. The autostereogram works by having repetitive patterns. To see depth in an autostereogram, you need to either cross or diverge your eyes so that they fixate separately on two different repeats of a repetitive pattern. In this way, you effectively get two different images to the two eyes.

Describe each system and provide at least one perceptual disadvantage for each of the following three-dimensional display methods: stereoscope A stereoscope is composed of two pictures mounted next to each other, and a set of lenses to view the pictures through. Each picture is taken from a slightly different viewpoint that corresponds closely to the spacing of the eyes. The left picture represents what the left eye would see, and likewise for the right picture. When observing the pictures through a special viewer, the pair of two-dimensional pictures merge together into a single three-dimensional photograph. Disadvantage: cannot be used for motion pictures

Describe each system and provide at least one perceptual disadvantage for each of the following three-dimensional display methods: Lenticular Lenses an array of magnifying lenses, designed so that when viewed from slightly different angles, different images are magnified. Each eye sees its own image Advantages- no viewing equipment, inexpensive Disadvantages- fixed viewing distance, resolution limited by lenses

Describe each system and provide at least one perceptual disadvantage for each of the following three-dimensional display methods: Variable mirror You have a display of which you are looking at the reflection of. The movement of the mirror depends upon image. They use a curved mirror to magnify depth. Advantages- no viewing equipment needed, you can get full color Disadvantages- very expensive projection equipment, limited viewing angles, small number of viewers

Describe each system and provide at least one perceptual disadvantage for each of the following three-dimensional display methods: Pulfrich phenomenon Pulfrich is based on the phenomenon of the human visual system processing images more slowly when there is less light as when looking through a dark lens. The most widely accepted theory for this illusion is that reducing the brightness of a stimulus to the retina of one eye causes relatively slower excitation of the photoreceptors and therefore a delayed processing of the image relative to the other eye. Disadvantage: Many ocular or neurological disorders that affect the visual pathway can produce a delay in signal transmission to the brain, creating a geometric disparity. The illusions created by this geometric disparity produce troublesome symptoms for individuals with a condition and is why many patients experience problems in everyday life as a result of the phenomenon.

Describe each system and provide at least one perceptual disadvantage for each of the following three-dimensional display methods: projected polarization To present stereoscopic images and films, two images are projected superimposed onto the same screen or display through different polarizing filters. Each eye sees a different image. This is used to produce a three-dimensional effect by projecting the same scene into both eyes, but depicted from slightly different perspectives. Several people can view the stereoscopic images at the same time. Disadvantage: The images for polarized glasses have to share the screen simultaneously, and therefore cannot have full resolution delivered to each eye simultaneously. A full 1080p picture results from image fusion; Possible headaches; Narrow vertical viewing angles compared to Active shutter 3D.

Describe each system and provide at least one perceptual disadvantage for each of the following three-dimensional display methods: Video-linked active glasses. No polarization in one eye, and when the image changes, you open the other eye. The image oscillates back and forth at about 120 Hz/second. 1. Two films take at two different positions 2. two views presented in alternate frames 3. Audience wears glasses which block one eye on alternate frames (usually driven by infrared signal) Advantages- large audience, motion, color Disadvantages- half normal intensity, expensive

Describe each system and provide at least one perceptual disadvantage for each of the following three-dimensional display methods: Anaglyph. Answer: The name given to the stereoscopic 3D effect achieved by means of encoding each eye's image using filters of different colors, typically red and cyan. Each of the two images reaches one eye, revealing an integrated stereoscopic image. The visual cortex of the brain fuses this into perception of a three dimensional scene or composition. Disadvantages: Ghosting: If some colour from the left image gets into the right eye (and vice versa) a faintly coloured "ghost" will be seen. Increasing the parallax (stereo depth) separates the two images and makes ghosting worse. Retinal rivalry: If the brightness (luminance) of the two images is not the same in each eye, the effect is unpleasant. Wrong colors: Each eye is getting only part of the RGB colour range. The viewer is always partially colour-blind and/or has retinal rival

If you were flying over New York City at a height of 1000 meters, would a 40 story (120 meters) building produce sufficient depth to exceed the disparity threshold? (assume that you have a 1 cm threshold at 10 meters). -Threshold disparity = 10 seconds of arc = 0.003 degrees or 0.0005 radians -Disparity D(θ) = ad/E2 = (0.064)(1000-120)/(1000 * 120) = 0.00047 = 0.047 %

Describe the steps for making a random-dot stereogram. RDS: stereo pair of images of random dots which when viewed with the aid of a stereoscope, or with the eyes focused on a point in front of or behind the images, produces a sensation of depth, with objects appearing to be in front of or behind the display level. 1. Create an image of suitable size. Fill it with random dots. Duplicate the image. 2. Select a region in one image. 3. Shift this region horizontally by a small amount. The stereogram is complete.

Binocular disparity is not incorporated into flight simulators. Why? How is motion parallax incorporated? Binocular disparity cues are only significant at ranges below 2m. With rare exceptions, aircraft don;t operate this close to other objects either in the air or on the ground. For this reason, visual scene simulations in flight simulators will only provide monocular cues to depth and distance. In a flight simulator, objects in the distance move more slowly in relation to objects that are more close, creating a cue of depth

You are watching a King Kong movie where a 10-story building falls in one second. What are you likely to see? If the original miniature was only 1 meter high but the building was intended to look 36 meters high, what do you do about the film rate? You are like to see a fast blurred object. The film rate would have to be sped up in order to make it appear as though the miniature was actually a 36 story building

Use projection theory to explain why a 3-D movie can produce a constant depth (when measured in terms of the percentage towards or away from the viewer) independent of where the observer is in the room. 3D movies are created by optical illusions, or a combination of cinematography and optics. The majority of 3D films are actually two films playing at the same time; each one has been designed so it's meant to be viewed by either your left eye or your right eye. The 3D glasses you wear filter those images, making sure they're interpreted correctly by your optical sensors (i.e. your eyes). Your eyes and brain naturally combine two images into one; it's the basic principle of sight. When this happens with the two images from a 3D film, you get a layered optical illusion that creates three-dimensional depth.

Describe and give a brief explanation of each of the following: Kinetic Depth Effect, shape constancy, relative vs. absolute depth cues, Pulfrich effect, horopter horopter - region of space that projects to corresponding points on the two retinae Pulfrich effect- When you filter an eye, the information has to enter brain slower. The image will seem to be behind the screen or in front of the screen depending up the filter of the eye. Advantages- inexpensive viewing equiptment, only one camera needed, motion allowed. Disadvantages- motion tied to depth, requires motion/depth choreography

A 50-foot wall is made with large bricks at the top and small bricks at the bottom. What unusual perceptions are you likely to have for objects at the top of the wall looking down? It is alot shorter than it seemed from the bottom. This is because of detail perspective.

Provide an example of the use of the following in filming miniatures in Lord of the Rings:  Atmosphere Perspective: Detail perspective: Familiar size: Atmosphere Perspective: Lothlorien - use of (christmas light) bulbs, blue background

Use size/distance theory to explain the moon illusion and the illusion that cars look like toys from the air. (If something is seen as further away, it will appear larger) We don't have enough depth cues for approximating the size of a car in the air.

On a graphics terminal you have created the image of a large rock on a field. The rock is intended to look 2 meters high. If the rock perceived as being much closer that you anticipated, what will happen to the perceived size? It will appear smaller (remember the moon/angle picture if this confuses you)

Describe and provide examples of two ocular cues for the perception of depth Temporal Cues: 1) Motion parallax - Motion parallax is a depth cue that results from our motion. As we move, objects that are closer to us move farther across our field of view than do objects that are in the distance. 2) Rate of acceleration: The rate at which some object falls gives some idea about the size of the object. (film example: if something should be seen as 100m but if it is only 1m, you should project it 10 times slower (sqrt(100/1))). 3) Kinetic Occlusion: When an object is positioned in front of another one relative to the eye, the further object can no longer be completely seen. The partially blocked object looks like it sits behind the other because of visual occlusion. This perceived obstruction is a very reliable cue for depth perception, which means that it produces depth perception even in situations with minimal information.

Describe and provide examples of four pictorial cues for the perception of depth. Pictorial cues: 1) Familiar size - pictures people take in front of leaning tower of pisa 2) Atmospheric perspective - air between me and the stuff reduces the contrast in the background (starwars - blue background to give a depth cue) 3) Linear persepctive - The school of Athens, Raphael, railroad, vietnamese war memorial 4) detail persepctive - pattern (detail) gets smaller with distance, brick size of fairytale castle in Disney World gets smaller on top 5) shape from shading - use of shadows, Mona Lisa 6) depth of field - (the distance btw the nearest and farthest objects in a scene that appear acceptably sharp in an image) Higher proportional depth range with increasing distance, tilt-shifted photography

Why were the miniatures so large in Lord of the Rings? Answer: Because bigger miniature would make the movie more realistic (he says in the video that the rule of thumb is, the bigger the miniature, the more realistic it is).

What is a scale composite? Provide an example. Answer: Take each separately in different scale and composite them in one, shrinking one in order to get the scale correctly. In Lord of the Rings, when hobbits/humans are together, take a shot with hobbits only and a shot with humans only and combine them together later.

What is forced perspective? How does it apply to the filming of Frodo and Gandalf together on the cart in Lord of the Rings. Why does motion of the camera make this difficult? What is the solution? Forced perspective is a technique that employs optical illusion to make an object appear farther away, closer, larger or smaller than it actually is. Using static camera, because hobbit - human height difference is 0.75:1, if frodo and gandalf in same scene, put frodo ⅓ distance away, in cart scene, frodo seating behind gandalf although it seems like they seat next to each other. Motion camera makes it difficult because then the distance between two objects change. In Lord of the Rings they used moving dolly for the actor's chair/desk so that the distance is preserved even when the camera is moving

Describe an example of how "point of view" was used by Mantegna. Answer: He places the view at the level of the begging man in order to create a visual bond between viewer and the painting's subject. This draws the viewer into the painting and make them feel as though they are experiencing the same moment as the subject in the painting

Explain why Johnny Lee's demonstration of depth on the Wii is so powerful. Answer: This demonstration showed that motion parallax is an incredibly powerful

Provide an example of the use of the following in filming miniatures in Lord of the Rings. Atmosphere - Adding a blue haze and lowering contrast of things that are that you want to seem further away allows the visual system to perceive it that way Perspective - forced perspective (static camera, because hobbit - human height difference is 0.75:1, if frodo and gandalf in same scene, put frodo ⅓ distance away, in cart scene, frodo seating behind gandalf although it seems like they seat next to each other) Detail - Where there were going to be close-up shots, the artists ensured the detail would stand up to scrutiny ( the steps ) Color Familiar size - actors wear large clothes and walk past hobbits. This works because we have a mental heuristic for how large a human body is

What is anamorphic art? Answer: A painting that needs to be seen in an angle that is different from normal viewing angle (uses distorted perspective, at least in the video)

Describe the depth cues available in a painting or photograph (when provided). Answer: The trinity - the first painting to demonstrate non-linear perspective One of Albert Durer's painting: multiple vanishing point perspective Leonardo Da Vinci: did lots of stuff (delicate contrast of light and dark: Mona Lisa) Raphael's figure study: lights and shade (late Renaissance, drew with theatrical light effect) Mantegna - plays around with perspective (emphasizes Christ's feet, painting becomes spectators etc) Raphael's School of Athens - paints masters of illusions (like Michelangelo) in the painting

Bruneleski in 1413 described what primary aspect of linear perspective? Answer: Parallel lines converge to a one point (vanishing point).

Before the renaissance, what evidence suggests that artists did not have a solid grasp of linear perspective? Answer: The lines composing the image do not converge to a single point. The images appeared flat because of this. During the renaissance, paintings were made that looked three dimensional

What technologies use additive color mixture? Which use subtractive color mixture? Answer: Color photographs on film use additive color mixture, while paints use subtractive (I believe).

Describe four color phenomena that are explained by opponent color theory that are not explained by trichromatic color theory. Answer: (1) color naming -- there are no reddish green or bluish yellow. (2) colored afterimages (3) simultaneous color contrast - color constancy (4) color naming with those that have anomalous color vision (5) Benham's top and temporal colors

According to opponent color theory what causes the perception of white? Answer: Opponent color theory - Our visual system maintains efficiency by measuring differences in the wavelengths being received by our three types of cones. There are three opponent color channels assigned to our cones: red v. green, blue v. yellow, and black v. white Variances in luminance cause our perception of white. There are cones that are achromatic (black and white color channels) and more sensitive to changes in brightness (leading to our perception of black and white respectively)

How does one make an Ishihara color test chart that finds protanopes and distinguishes them from deuteranopes? Answer: (1) Find two colors along a color confusion line for the test in question (i.e protanope vs. deuteranope) (2) using spots, make a number with one color and the background of the other (3) randomize the intensities and sizes of the stops (4) Option: make a number of lower contrast that will be visible to subject of the test

What is wrong with the description of some individuals as 'color blind' ? Answer: It is more of an inability to distinguish between colors than not being able to see the colors.

Use the CIE diagram to describe the range of colors seen by a dichromat. What is represented by a confusion line? Answer: Represents all the colors that are confused by a person with a certain color problem. For example, a protanope has many confusion lines. Look at the "protanope" graph on his slides to see all of the lines.

Why do television stations transmit a YIQ color signal to an RGB phosphor television? Why is this used for television broadcasting? 1. Allows compatibility with black and white televisions (Y Signal) 2. Allows reduced bandwidth: Luminance signal sent at higher bandwidth. Y = 4.2 MHz, I = 1.3 MHz Q =0.5 MHz

What is the difference between LUV(UVW) and XYZ color space? Answer: the 1931 CIE x,y Chromaticity Diagram (or xyYdiagram) was inadequate because the two-dimensional diagram failed to give a uniformly-spaced visual representation of what is actually a three-dimensional color space. CIE proposed modifying the u,vdiagram and supplying new (u',v') values. This was done by multiplying the v values by 1.5. While the representation is not perfect (nor can it ever be), the u',v' diagram offers a much better visual uniformity. This can be seen by comparing the following illustration of the u',v' diagram with the x,y diagram at the top of this section The lines in theu',v' diagram represent the same as in the x,y illustration, only here we can see the lines are more nearly uniform throughout the diagram.

Explain the concept of negative primaries in a color matching task. Answer: Negative light: when a light must be subtracted to arrive at a particular coordinate location Imaginary primaries: coordinate axes outside of color space. Used so that all colors can be in terms of positive coordinates.

Can I match a mixture of 585 nm and 500 nm (50% of each) with a color on my computer screen? What would be the RGB output? Answer: Light Green

If R and G are fixed at 100, what colors can be produced by varying the amount of B? Answer: From yellowish green to purple

Why does CIE use 'imaginary' primaries? What is represented by points outside the CIE chart? For CIE questions, you can assume you will have a chart printed out for you. Answer: Imaginary primaries are coordinate axes outside of color space- Michelle says that they were arbitrarily chosen (just math to make the axes fit). They are perfectly good coordinates, but not actually colors. Used so that all colors can be put in terms of positive coordinates. They are mathematically plausible but not producible or perceived.

What is evidence that color names are not culturally determined. What did Berlin and Kay show about the evolution of color names? Answer: In fact, there are a lot of similarities across cultures about where people place color boundaries. Berlin and Kay found that if a language only has 1-2 color names, they are often assigned to black and white. If a language has 3 color names, it adds red, with 4 color names, it adds green/yellow, and so on. Therefore, throughout cultures there is a certain continuity in color naming.

According to Livingstone, why do equiluminant colors look unusual? Answer: This is because when looking at equiluminant colors, the "what" system is activated, and we can identify a particular object. However, the "where" system is not activated, so we can not see position or motion. When we cannot distinguish the position of an object, it may the object/image look jittery or unstable. Page 66.

What is Livingstone's theory regarding the origin of the Mona Lisa's elusive smile? Answer: (Livingstone p.73) - Livingstone believes that Leonardo da Vinci's intention was to provide course details around her mouth that suggest more of a smile, while the fine details make it seem much less like a smile

What is change blindness? What does it say about the information we code in the natural world? Answer: Change blindness is a psychological phenomenon that occurs when a change in a visual stimulus goes unnoticed by the observer. We don't actively encode a lot of information about the natural world, we just constantly reference and extrapolate information. We fill in the gaps.

Describe a perceptually perfect (i.e., efficient) visual display. Include in your discussion. Answer: A. Visual field- displays that use literally your entire field, as you go further away from periphery, you need to display things bigger to convey that info B. Intensity range-ratio of intensity levels you can see C. Number of intensity levels- 2^8 - 2^10 intensity levels (8-10 bits) D. Visual acuity(100 lines or 50 cycles per pixel) E. Temporal acuity- our refresh rate(1/20sec)- anything that flashes quicker than that, we would not notice it is flashing F. Color- RGB triangle inside the CIE table,, we can only make colors inside the RGB trinangle G. Motion-

Provide two lines of evidence that we are especially sensitive to biological motion? Answer: Cutting and Koslowski (1978)  given only point-light walkers to watch (a moving image with lights on representing major joints on the body), people have a high accuracy for detecting the sex and age of the walkers, but when the images are static and do not move, this accuracy drops significantly. Shoulder and hip differences make a big difference in determining the gender. Pinto and Bertanthal (1994) Infants at four months can differentiate biological versus non-biological movement (Pinto and Bertanthal, 1994)

In the video showing two lamps playing with a ball, why do the lamps look alive and seem to have personality? Answer: The lamps follow certain biological rules to motion. For example, when they jump and return to the ground they are bent at the "knees" to reduce the jerk downwards to the ground. The change in acceleration is known as jerk. Using biological motion, could tell if something is cat or dog, lifting something heavy vs pretending to lift something heavy. Thus, it is a powerful tool.

What is the relation between the high threshold for motion and visual acuity? How fast must something move before one loses the ability to resolve spatial detail? Temporal Sensitivity and Motion There is a high threshold of 2 arcdeg/sec before visual acuity drops. High threshold for motion means: How fast can something move and still be visible? Acuity drops with increasing frequency

Describe and provide examples of 5 ways to make a spot. Answer: appear to move. Move the dot  Adapt to motion then observe the dot  Autokinetic: Observe the dot without references  Induced motion: move the reference frame  Stroboscopic/apparent motion: flash successive dots

Use a space/time plot to explain why blur is sometimes introduced into movies with fast motion? Answer: Motion blur is a natural effect when you film the world in discrete time intervals. Without motion blur, animation will appear to jump and will not look fluid. When the frame rate of a movie is too low, your mind will no longer be convinced that the contents of the movie are continuous, and the movie will appear to jump (also called strobing). When you blur, there is something continously moving across your vision and does not appear to jump. From the graphs, the blurring makes the object look less jumpy because the space/time jump is artificially decreased. See graphs.

What is the relation between spatial resolution, temporal resolution and velocity, for the perception of movement in time sampled displays like cinema or television? Spatio-temporal Aliasing (Motion Lecture) with frame rates low compared to velocity, sampling artifacts become visible. This means that given a certain spatial resolution, if the patterns move very fast relative to the temporal resolution, the patterns will appear to jitter as they move. This is why they use blurring in direction of motion (e.g., leaving shutter open) can reduce the sampling artifacts.

Provide two example's of art that take advantage of the acuity limitations in the visual periphery. (Livingstone) Rue Montorgueil in Paris, Festival of June 30, 1878 by Claude Monet- It depicts a French flags waving in a scene—the flags in the periphery are not as precise as those at the center. This is realistic because the acuity in our periphery is not as exact as that in our fovea. Madame Henriot by Pierre-Auguste by Renoir- The face (especially the eyes) are very clearly painted, while the rest of the woman's body is not detailed, almost blending into the background. This directs our gaze to the woman's eyes.

What are the advantages of filming at 60 Hz or better? How does this improve the appearance over traditional techniques. What are the disadvantages? Answer: The interval of still images is increased to 60 frames per second, so it is closer to reality (which has continuous images). You therefore don't need motion blur. Disadvantages are that it creates higher frame rates, which gives the soap opera effect. Motion is more smooth with higher Hz, but another disadvantage is that it takes more physical film to create.

What are the steps to the Remote Sensing Process? Identifying the Problem; Statement of the Problem Data Collection Data-to-Information Conversion Information Processing

What are some limitations of remote sensing? 1.The greatest limitation is that it is often oversold. Remote sensing is not a panacea that provides all the information needed to conduct physical, biological, or social science research. It provides some spatial, spectral, and temporal information of value in a manner that we hope is efficient and economical 2.Human method-produced error may be introduced as the remote sensing instrument and mission parameters are specified. Human beings select the appropriate remote sensing system to collect the data, specify the various resolutions of the remote sensor data, calibrate the sensor, select the platform that will carry the sensor, determine when the data will be collected, and specify how the data are processed. 3.Powerful active remote sensor systems that emit their own electromagnetic radiation (LIDAR, RADAR, SONAR) can be intrusive and affect the phenomenon being investigated. Additional research is required to determine how int

What are some advantages of remote sensing? 1. Remote sensing is unobtrusive if the sensor passively records the EMR reflected or emitted by the object of interest. Passive remote sensing does not disturb the object or area of interest. 2. Remote sensing devices may be programmed to collect data systematically, such as within a 9 9 in. frame of vertical aerial photography. This systematic data collection can remove the sampling bias introduced in some in situ investigations. 3. Under controlled conditions, remote sensing can provide fundamental biophysical information, including x,y location, z elevation or depth, biomass, temperature, and moisture content. 4. Remote sensing-derived information is now critical to the successful modeling of numerous natural processes, such as water-supply estimation; eutrophication studies, and nonpoint source pollution; and cultural processes such as land-use conversion at the urban fringe, water-demand estimation, and population estimation.

How can error be introduced during the in situ data collection process - method-produced error? Answer: Scientists could collect data in the field using biased procedures such as the use of a biased sampling design or the improper use of a piece of equipment. Also, the data collection measurement device may be calibrated incorrectly.

How can error be introduced during the in situ data collection process- intrusive 2? Answer: Similarly, a scientist collecting a spectral reflectance reading could inadvertently step on the sample site, disturbing the vegetation canopy prior to data collection.

How can error be introduced during the in situ data collection process- intrusive 1? Answer: Unless great care is exercised, the scientist can actually change the characteristics of the phenomenon being measured during the data collection process.

Give an example of in situ data collection. Answer: A scientist collecting leaf-area-index (LAI) measurements of soybeans using a ceptometer that measures the number of "sunflecks" that pass through the vegetation canopy. The measurements are made just above the canopy and on the ground below the canopy.

What is an in situ data collection? Answer: Measurements made at the actual location of the object or material measured, in contrast to remote sensing.