# Computer Graphics Part 6b (Shading)

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 Author: Anonymous ID: 217119 Filename: Computer Graphics Part 6b (Shading) Updated: 2013-05-01 19:22:53 Tags: computer graphics informatics science Folders: Description: University of Edinburgh School of Informartics Copmuter Graphics (Level 10) Revision Cards created by Simon M. Show Answers:

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1. What is the difference between the shading and illumnination model?
While the illumination model computes the color of sample points, the shading model is the process that colors the whole surfaces.
• Flat shading (lighting computation is done once per polygon) -> less compputation needed
• Phong shading (once per vertex) -> heavy computation needed
4. What is the major problem with the flat shading model?
• suffers from matchband effect
• humans are very sensitive to sudden change of brightness
• the artefact remains even if polygon number is increased
5. Exaplin how the Gouraud shaing works...
6. how to compute vertex normals and their funciton
7. What is the major problem with Gouraud shading?
8. Describe the Gouraud Shading model in 3 steps!
9. Describe the Gouraud Shading model in 3 steps!
10. Name the major problem(s) with interpolation shading and the solutions...
• 1. In some cases a polygon might have additional vertices between two corners that belong to neighboring polygons and f-up the average. (sol1; subdivide into triangles, problems does not occur, sol2; introduce 'ghost' vertex that shares that vertex' values)
• 2. Inside/Outside problem (add small polygon strips along edges or test angle and threshold to defeat averaging)

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