# Computer Graphics Questions & Answers – Three Dimensional Concepts

This set of Computer Graphics Multiple Choice Questions & Answers (MCQs) focuses on “Three Dimensional Concepts”.

1. How many axes does a three-dimensional graphics consists of?
a) One axis
b) Two axes
c) Three axes
d) Six axes

Explanation: A three-dimensional graphics consists of three axes namely the x axis, the y axis and the z axis. These axes simulate the length, width and height of a 3-dimensional object.

2. Which of the following is the most commonly used boundary representation for a 3-D graphics object?
a) Data polygon
b) Surface polygon
c) System polygon
d) Volume polygon

Explanation: Surface polygon is the most commonly used boundary representation for a 3-D graphics object. The object’s interior is enclosed by this surface polygon. In this method of representation, set of polygons are stored for description of the object.

3. A three-dimensional object can be represented using which of the following representation?
a) Equation
b) Function
c) Point
d) Polygon

Explanation: A three-dimensional object can be represented by using an equation representation. The equation for a 3-dimensional object contains 3 variables x, y and z and 4 coefficients A, B, C and D.

4. Which of the following equation correctly represent a 3 D plane?
a) Ax + By + Cz = 1
b) Ax + By + Cz = 0
c) Ax + By + Cz + D = 1
d) Ax + By + Cz + D = 0

Explanation: The equation that correctly represent a 3 D plane is Ax + By + Cz + D = 0. Where x, y, z is any point on the plane, and the coefficients A, B, C, and D are constants describing the spatial properties of the plane.

5. Which of the following transformations are most common that are applied on three-dimensional objects?
a) Translation
b) Scaling
c) Rotation
d) Translation, Scaling, Rotation

Explanation: Most common transformations that are applied on three-dimensional objects are Translation, Scaling and Rotation. Translation refers to moving of an object from its original position. Scaling refers to zooming in or out the size of an object. Rotation refers to rotating an object about its axis.
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6. How many types of projections are present in 3 D graphics?
a) 2
b) 3
c) 5
d) 7

Explanation: In 3 D graphics there are 5 types of projections namely – Parallel Projection, Orthographic Projection, Oblique Projection, Isometric Projection and Perspective Projection.

7. Which of the following refers to the shapes created by union, intersection and difference of given shapes?
a) Wire frame model
b) Composite transformation
c) Constructive solid geometry methods
d) Destructive solid geometry methods

Explanation: Constructive solid geometry methods refers to the shapes created by union, intersection and difference of given shapes. In a constructive solid geometry approach, a solid model of an object is created by using the three-dimensional geometric entities, known as primitives.

8. Which of the following refer to a model that represent all the dimension of an object external as well as internal?
a) Wire frame model
b) Constructive solid geometry methods
c) Composite transformation
d) Destructive solid geometry methods

Explanation: Wire frame model is used to represent all the dimension of an object external as well as internal. The wireframe model is made by connecting all the vertices of an object by either a straight line or a curve. In this model every vertex is connected with each other.

9. In which of the following, the projection plane is intersected by all three x, y and z axes at the same distances?
a) Cabinet projection
b) Perspective projection
c) Isometric projection
d) Cavalier projection

Explanation: isometric projection is a projection where the projection plane intersects each coordinate axis in the coordinate system at an equal distance. In this projection parallelism of lines are preserved but their angles are not preserved.

10. Which of the following constitutes of subcategories of Perspective Projection?
a) Cavalier projection, Cabinet Projection
b) One point, Two point, Three point
c) Front projection, Top projection, Side projection
d) Orthographic projection, Oblique projection

Explanation: The Perspective Projection consists of – One point, Two point, Three point. One point perspective projection is simple to draw. Two point perspective projection gives better impression of depth. Three point perspective projection is most difficult to draw.

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