Which of the following statements is/are True regarding the solution
2018
Which of the following statements is/are True regarding the solution to the visibility problem in 3D graphics ?
S1 : The Painter’s algorithm sorts polygons by depth and then paints (scan - converts) each Polygon on to the screen starting with the most nearest polygon.
S2 : Backface Culling refers to eliminating geometry with backfacing normals.
Code :
- A.
S1 only
- B.
S2 only
- C.
Both S1 and S2
- D.
Neither S1 nor S2
Attempted by 108 students.
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Correct answer: B
Answer: S2 only
S1 is incorrect because the Painter’s algorithm sorts polygons by depth and paints starting with the farthest polygons first, so nearer polygons overwrite farther ones. The statement in S1 says painting starts with the nearest polygon, which is the reverse of the correct process.
S2 is correct: backface culling removes polygons whose normals face away from the camera, since such faces are not visible from the current view. Implementation typically checks polygon winding or the sign of the dot product between the view direction and the polygon normal.
Notes: The Painter’s algorithm can fail for cyclic overlapping polygons and often requires splitting polygons to work correctly. Backface culling is safe for single-sided surfaces but should be disabled for double-sided materials.