Computer Graphics Part 9 (Hidden Surface Removal)

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Author:
simon123
ID:
217154
Filename:
Computer Graphics Part 9 (Hidden Surface Removal)
Updated:
2013-05-01 22:38:59
Tags:
computer graphics informatics science
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Description:
University of Edinburgh School of Informartics Copmuter Graphics (Level 10) Revision Cards created by Simon M.
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  1. List methods of hidden surface removal
  2. What is the major problem with the painters algorithm?
    Doesnt work in cases in which one polygon is above and below another polyogn at the same time... (or other cases)
  3. explain the basic Z-buffer idea!
  4. advantages(5) and disadvantages(2) of z-bufer
  5. z- buffer performance
    • memory overhead: O(1)
    • time to resolve visibility to screen precision: O(n) [n=number of polygons]; needs to be combined with other culling methods to reduce complexity
  6. BSP tree
    • sort polygons according to depth, and only draw those close to the viewer
  7. Displaying a BSP-tree: back to front (4 points)
  8. Explain how front-to-back works differently to back-to-front and what the advantage is


    use active edge table to hold data on filled pixels, each scan line holds a record of filled pixels
  9. BSP tree advantages/disadvantages; combination with z-buffer
    • disadvantage; tree computation is costly
    • advantage; once tree is created, cheap to check visibility -> efficient when objects dont change often in scene

    • render static objects first combined with z-buffer
    • then render dynamic objects (doors, characters) without z-buffer
  10. Portal Culling
  11. classifiying techniques: object space (3) and image space (1)
    object space techniuqes; applied before vertices are mapped to pixels - painters alogirthm, BSP trees, portal culling

    image space techniques, applied while vertiecs are rasterized - z-buffering
  12. Exapln how back face culling is done

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