1. Many of the figures from this book may be reproduced free of charge in scholarly articles, proceedings, and presentations, provided only that the following citation is clearly indicated: “Reproduced with the permission of the publisher from Computer Graphics: Principles and Practice, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley. Copyright 2014 by Pearson Education, Inc.” Reproduction for any use other than as stated above requires the written permission of Pearson Education, Inc. Reproduction of any figure that bears a copyright notice other than that of Pearson Education, Inc., requires the permission of that copyright holder.

2. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.1 The components of the visual system.

3. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.2 Three 41 × 41-pixel images. The top image has all pixel values 118; the middle has all pixel values 128; the bottom has all pixel values 128, except the center, which is 255. The L 2 distances from the top image to each of the others are approximately equal, but this does not match our own understanding of “sameness.”

4. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.3 Close up, you see Einstein; from a distance, you see Marilyn Monroe. (Image courtesy of Aude Oliva, MIT.)

5. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.4 Light enters the eye through the pupil, then passes through the lens and vitreous humor, and arrives at the retina.

6. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.5 Light from point A is in focus when it arrives at the surface at right; point B is out of focus.

7. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.6 The raw response of receptors in the bright and dark regions (in blue, at top), the lateral inhibition amounts (in red, middle), and their difference—the actual response—shown in green at the bottom. Notice the enhanced contrast at the edge between light and dark, indicated by the dotted line.

8. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.7 The dark-adapted eye’s response to light “saturates” at a fairly low stimulus level; the light-adapted eye cannot detect differences between various low-light-level stimuli.

9. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.8 All the center squares have the same lightness; the apparent lightness, however, is profoundly influenced by the surrounding squares.

10. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.9 The ratio of the center square’s darkness to the surrounding square’s darkness is approximately the same in each example; you tend to see the center squares as exhibiting far less variation in lightness than those in the previous figure.

11. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.10 The diagonal line in (a) seems to pass behind the vertical strip. You strongly sense the two diagonal segments are part of a continuous whole, as shown in (b), rather than each terminating behind the vertical strip, as in (c).

12. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.11 Which of (a) and (b) seems to be a single continuous straight line passing behind a strip, and which looks like the two segments are parallel but not part of the same line? Place a straightedge on the figure to determine the truth.

13. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.12 When we truncate the vertical lines so that the obscuring strip seems to be a plane parallel to one containing the line, the illusion from Figure 5.11 disappears; the same effect happens when the strip is given a texture that indicates this tilted orientation.

14. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.13 (a) A ball moves above a three-sided tray without shadows; its motion is not strongly determined. (b) and (c) Shadows force an interpretation of the motion as being in a vertical or horizontal plane.

15. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.14 The appearance of a contact shadow tells us quite a lot about shapes and their relationship. You perceive the two identically drawn forms quite differently when shown their nonidentical shadows.

16. From Computer Graphics, Third Edition, by John F. Hughes, Andries van Dam, Morgan McGuire, David F. Sklar, James D. Foley, Steven K. Feiner, and Kurt Akeley (ISBN-13: 978-0-321-39952-6). Copyright © 2014 by Pearson Education, Inc. All rights reserved. Figure 5.15 The grid of crosses is rotated about its center at a speed approaching ten seconds per complete rotation. The user is instructed to fixate on the center of rotation. After a moment, one or more of the other dots in the image seem to disappear.