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Computer Graphics

12.7 Review Questions

1. "Light exhibits dual nature". Justify this sentence.
2. According to tri-chromaticity theory of light, S= r (red) +g (green) +b (blue). Explain.
3. “An arbitrary light S with spectral distribution P(λ) can be described by adding together the
respective amounts of the CIE primaries". Explain with equations.
4. “A color cube can be used to specify the colors". Explain.

5. RGB color values can be converted to HIS values. Explain the conversion method with the
equations.
6. "NTSC YIQ model is considered as a linear transformation of the RGB color model.” Explain.
7. "Constant shading is the easiest shading model for a polygon.” Explain.
8. "Constant shading is useful only when some assumptions are true". Explain those assumptions.

9. "Gouraud shading provides much better image than constant shading.” Explain.
10. "Phong shading method consumes relatively more time.” Explain.
11. "The chromaticity co-ordinates (x, y) can be converted into a specific color in the XYZ color space.”
Briefly explain with equations.
12. "The XYZ co-ordinates of a composite RGB color can be expressed in terms of a transformation
matrix.” Explain.
Answers: Self Assessment
1. (a) True (b) True (c) False
(d) True (e) False (f) True

2. (a) White light (b) Thomas Young, Hermann Von Helmholtz
(c) Luminance (d) Indexed-color (e) Diffuse
3. (a) Luminosity (b) I=Iaka+Ip (kd cos(θ) + kscosk(φ)) (c) Faceted shading
(d) S=r+g+b (e) Constant based on light source
12.8 Further Readings

Gutierrez,M., Vexo,F., & Thalmann, D.(2008). Stepping into Virtual Reality. Springer-
Verlag London Limited.
Angel, E. Interactive Computer Graphics: A Top-Down Approach Using Open-GL. 5th
Edition. Pearson Education.
Shirley, P., & Marchner, S. (2009). Fundamentals of Computer Graphics. 3rd Edition.
A.K. Peters, Ltd.
Xiang. Z., Plstock. R. (2006). Computer Graphics. 2 Edition. Tata McGraw Hill.
nd
http://portal.acm.org/citation.cfm?id=806793
http://www-graphics.stanford.edu/courses/cs448b-02-spring/04cdrom.pdf
http://www.articlesbase.com/science-articles/characteristics-of-light-3289311.html
http://www.csit.parkland.edu/~dbock/Portfolio/Content/Lights.html

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