Mumbai university > Comp > SEM 4 > Computer Graphics

Marks: 10M

Year: Dec 2014 , Dec 2015

Sweep representations are used to construct 3D object from 2D shape that have some kind of symmetry.

For example, a prism can be generated using a translational sweep and rotational sweeps can be used to create curved surfaces like an ellipsoid or a torus.

In both cases, you start with a cross-section and generate more vertices by applying the appropriate transformation.

More complex objects can be formed by using more complex transformations. Also, we can define a path for a sweep that allows you to create more interesting shapes.

Translational sweep:

i. Define a shape as a polygon vertex table as shown in figure 33 (a).

ii. Define a sweep path as a sequence of translation vectors figure 33 (b).

iii. Translate the shape; continue building a vertex table figure 33 (c).

iv. Define a surface table figure 33 (d).

Rotational sweep:

i. Define a shape as a polygon vertex table as shown in figure 34 (a).

ii. Define a sweep path as a sequence of rotations.

iii. Rotate the shape; continue building a vertex table as shown in figure 34 (b).

iv. Define a surface table as shown in figure 34 (c).