Page 176 - DCAP504_Computer Graphics

Unit 11: Hidden Surfaces

11.11 Review Questions

1. “A surface is considered visible if it has the minimum Z value.” Comment.
2. “Binary Space Partitioning tree is an algorithm independent of the viewpoint location.” Justify.
3. “The visible plane occludes the planes having higher Z-values at corresponding pixel locations.”
Discuss?
4. “The Warnock algorithm is a resolution dependent method. “ Discuss?

5. “Hidden surface determination is very much essential to render an image properly.” Give reason
behind it?
6. “The most important reason for using ray-tracing method is to create realistic renderings of
pictures.” Comment.
7. “The depth calculation is then done to find which polygon is nearest to the view plane.” Justify.

8. “Only those surfaces or portions of the object are visible which are drawn in counter-clockwise
direction.” Justify.
9. “The processing of scan lines is done from left to right.” Explain why?
10. “A root-node has pointers to all the eight sub-nodes.” Justify.
11. “If the smallest z-value for a polygon is greater than the highest z-value on the other polygon, then
the former polygon is in front of the latter.” Comment.
12. “If a node is found to be completely obscured it is eliminated from further processing.” Discuss.
Answers: Self Assessment

1. (a) False
(b) True
(c) False
(d) True
(e) True
(f) False

2. (a) Hidden line
(b) Minimum
(c) C-buffer
(d) BSP tree
(e) Ray-tracing
3. (a) Back space
(b) It requires additional code to do transparent surfaces

(c) Object space method
(d) Edge tree
(e) Area subdivision method

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