UGC NET CSE | June 2019 | Part 2 | Question: 29

Question

In the context of 3D computer graphics, which of the following statements is/are true?

P : Orthographic transformations keep parallel lines parallel.

Q : Orthographic transformations are affine transformations.

Select the correct answer from the options given below:

• A. Both P and Q
• B. Neither P nor Q
• C. Only P
• D. Only Q

Answer 1

correct ans is A

Orthographic projections are parallel projections. Each line that is originally parallel will be parallel after this transformation.

Orthographic projection (sometimes referred to as orthogonal projection, used to be called analemma[a]) is a means of representing three-dimensional objects in two dimensions. It is a form of parallel projection, in which all the projection lines are orthogonal to the projection plane,

In Euclidean geometry, an affine transformation, or an affinity (from the Latin, affinis, "connected with"), is a geometric transformation that preserves lines and parallelism (but not necessarily distances and angles).

The orthographic projection can be represented by a affine transformation.

https://en.wikipedia.org/wiki/Affine_transformation

https://en.wikipedia.org/wiki/Orthographic_projection

 

 

Answer 2

P: orthographic projection doesn't always keep parallel lines parallel. 

Q: It is a form of parallel projection, in which all the projection lines are orthogonal to the projection plane, resulting in every plane of the scene appearing in affine transformation on the viewing surface.

Only Q is true. so option D is correct. 

Comments

if q is true then p is true as well.

see https://en.wikipedia.org/wiki/Affine_transformation