ELEC 200 - Engineering Graphics - Fall 2004

Midterm Examination

Points are represented as column vectors throughout.
Calculators and single-page formula sheets are permitted.
Answer any 3 of the 5 questions.
You have 45 minutes.

  1. Show that a reflection across the yz plane, followed by a reflection across the zx plane, is equivalent to a rotation about the z axis.

  2. Let Q be the matrix of endpoints of an arbitrary figure in space, let L be the matrix of endpoints of an arbitrary line in space, and let be an arbitrary angle. Write a MatLab function that rotates Q about L by and returns the result. Use 3D homogeneous coordinates.

  3. Let T(a, b, c) be the matrix that translates from the origin to point (a, b, c) and let S(s) be the matrix that scales by a factor of s in all 3 dimensions. Is it true that T(a, b, c) S(s) = S(s) T(a/s, b/s, c/s)? Prove your answer.

  4. Let Q be the matrix of endpoints of an arbitrary figure lying in the xy plane and let L be the matrix of endpoints of an arbitrary line lying in the xy plane. Write a MatLab function that reflects Q across L and returns the result. You may use 2D or 3D homogeneous coordinates.

  5. Derive the perspective transformation that looks at the origin from the point (0, 3r, -4r).