In perspective projection (from 3D to 2D), objects behind the centre of…
2016
In perspective projection (from 3D to 2D), objects behind the centre of projection are projected upside down and backward onto the view-plane. This is known as _____.
Answer: C. View confusion — Answer: View confusion Explanation: In perspective projection, when a point or object lies behind the centre of projection (the camera), the projection rays…
- A.
Topological distortion
- B.
Vanishing point
- C.
View confusion
- D.
Perspective foreshortening
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Correct answer: C
Answer: View confusion
Explanation: In perspective projection, when a point or object lies behind the centre of projection (the camera), the projection rays intersect the view plane on the side opposite to the object. As a result, the projected image appears upside down and reversed; this phenomenon is called view confusion.
Cause: Rays from points behind the centre of projection pass through the centre and hit the view plane on the opposite side, producing inverted and mirrored coordinates.
Effect: The image of the object is upside down and backward on the view plane.
Practical handling: Graphics systems typically avoid this by clipping or rejecting points behind the camera (for example, using a near clipping plane or by checking camera-space z) so only points in front of the centre of projection are rendered.
Distinction from related terms:
Vanishing point: The point where sets of parallel lines in 3D appear to converge in the projection; not about inversion.
Perspective foreshortening: The apparent shortening of an object's dimension along the view direction with distance; does not produce an upside-down or mirrored image.