Last Updated February 22, 2010

Hidden surface removal

1. What are backfaces? How are backfaces in a scene identified?
2. Backfaces need to be removed from a mesh before rendering. How is a backface determined?
3. Given a eye position of (-5,0), and a polygon containing the point (3,1) and a normal to the polygon of (-1,1). Is this polygon a backface? Show your calculations fully.
4. Describe an efficient method to remove hidden surfaces while rendering.  
5. What is the heedless painters hidden surface removal algorithm?
6. Why are double buffers used in graphics? How are they used?
7. Discuss the relative merits and demerits of the following HSR methods.
   • Depth ordering with occlusion
   • Depth buffer
   • Scan line method
8. How does the Depth buffer method efficiently determine the depth of a point on a polygon?
9.                                                                                   
10. When viewing a polygon mesh describe in detail how hidden surfaces are removed using the depth buffer (Z-buffer) method. How do we calculate the depth of a face?
11. Describe in detail the Scan-Line HSR algorithm. Explain the role of the Active Edge List and Edge table. How are these data structures maintained?
12. OpenGL uses a double buffer model for rendering. What is “Double Buffering”, and what are the advantages of double buffering? What is “Triple Buffering”?
13. How can you perform HSR if the faces are sorted prior to rendering? How do you avoid “overdraw”?

© Ken Power 1996-2016