# Midterm exam retake
https://3d.bk.tudelft.nl/courses/backup/geo1004/2020/data/midterm.md
2020-04-03 14:00

Name:  
Student number:

This midterm exam is worth 10% of the final mark for the course.

There are 16 points in total:
* 7 multiple choice questions [1 point each, 7 points total]. For this section, there is **negative marking**. That is, for each question, if you get it completely right you get 1pt, if you answer nothing you get 0pts, and if you get it wrong you get -1pt. In questions with multiple answers, each answer will give you the proportional amount, eg -1/2pt and 1/2pt. You cannot get less than 0pts in total for these questions.
* 3 short answers [3 points each, 9 points total]. The mark for each question will range from 0pts to 3pts depending on how well the question is answered.

First, you should download this file to your computer.
Then, answer the questions on the downloaded file by:
* for the multiple choice questions, putting a mark between the square brackets (eg [X]);
* for the short answer questions, writing your answer after the question (use as many lines as you want).

If you have any questions, send Ken (kenohori#5365) a DM on Discord. Email (k.ohori@tudelft.nl) is also fine.

Submit your answers by uploading this file (with your answers) here:
https://www.dropbox.com/request/9MzeH7yzGRK3VNjIPBry

**We are asking for your honesty to make this a closed-book exam**. Help us push back against implementing invasive techniques in remote education. You have 1 hour to do this exam. Files uploaded after 15:05 will not be accepted (so avoid problems by uploading at 15:00 at the latest).

## Multiple choice questions (7 points)
[Only one good answer, unless otherwise stated]

1. An example of a data structure is:  
	[] vector  
	[] UML  
	[] the half-edge  
	[] point clouds

2. In a mesh data structure, holes can be handled by: [3 correct answers]  
	[] using bridge edges  
	[] carefully storing them in a specific order  
	[] storing them as attributes  
	[] splitting objects

3. In extruding a 3D building model from a 2D roof partition: [2 correct answers]  
	[] faces in the roof partition can become walls in the 3D model  
	[] edges in the roof partition can become faces in the 3D model  
	[] vertices in the roof partition can become faces in the 3D model  
	[] vertices in the roof partition can become edges in the 3D model  

4. Some characteristics of voxels are: [2 correct answers]  
	[] making robust algorithms simpler  
	[] being more compact than meshes  
	[] having a built-in precision limit  
	[] efficiently representing multiple objects at the same location

5. Which one of the following statements concerning the Delaunay tetrahedralisation is **false**:  
  [] the dual of a Delaunay triangular face is a Voronoi edge  
  [] if a given vertex 'v' is incident to 17 tetrahedra, the dual of 'v' (a Voronoi 3-cell) will have exactly 17 faces  
  [] the dual of a Delaunay edge is a Voronoi face  
  [] the sphere circumscribed to each tetrahedron is empty of any other vertices in the Delaunay tetrahedralisation

6. The following is **not** commonly used as a primitive in CSG:  
	[] half-spaces  
	[] convex polyhedra  
	[] primitive solids  
	[] Nef polyhedra

7. A Bézier curve **must** pass through:  
	[] all points  
	[] only the data points  
	[] only the control points  
	[] possibly no points  

## Short answer questions (9 points)

8. Give three characteristics of the data driven building reconstruction approach.

9. What can we do to reduce the size of a voxel model? (without changing the area covered or the size of the voxels)

10. What is the degree of a Bézier curve?