Computer Graphics Part 5b (View Transformation)

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Computer Graphics Part 5b (View Transformation)
2013-05-01 14:24:09
computer graphics informatics science

University of Edinburgh School of Informartics Copmuter Graphics (Level 10) Revision Cards created by Simon M.
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  1. What is the main reason for computing the View Volume in the View Transformation Process? list one other problem with view projection
    • During view projection, depth information is lost, which is needed for clipping / hidden surface removal.
    • another problem: object behind camera are projected to the front of camera
  2. box vs frustum?
    frustum is the 3d view volume for a perspective projection, while box is for parallel.
  3. What is the problem with View Frustum and what is the solution?
    It is hard and costly to check whether object lie within a frustum. Convert the frustum to canonical view volume using perspective transformation for easier calculation of hidden surfaces
  4. matrix for transforming a view frustum into a canonical view volume
  5. Example calculation
    • (divide by w to get 3D cartesian cooridnates)
  6. what does clipping mean? name two approaches
    need to remove/clip  objcets outside canonical view volume.

    • Cohen-Sutherland algorithm: clipping liens
    • Sutherland-Hodgman algorithm: clipping polygons
  7. Explain Sutherland-Cohen algorithm.
    • 9 sections, outocdes: tbrl-0000/1111 (to be really lost)
  8. what is trivial accept? and how to check?
  9. What is trivial reject? and how to check?
  10. line intersection check
  11. Name for polygon clipping algorithm?
    Sutherland-Hodgman algorithm
  12. Sutherland Hodgman - 4 types of edges
  13. describe sutherland-hodgman algorithm
    • traversing the polygon edges using the following method: