Dr Neil Dodgson,
University of Cambridge
Computer Laboratory
Part II course, 1998
Lecture 2 Index
...back to lecture 1
Part A: Conics, quadrics, and superquadrics
Part B: Generative models
Part C: Converting primitives to polygons
on to lecture 3...
2C) Converting primitives to polygons
When using PSC any primitive shape, be it sphere, torus or
sweep, must be converted to polygons in order to be drawn.
A swept surface may be easily converted to polygons by converting the
outline of the 2D cross section to a polygon, and converting the sweep
path to connected set of line segments. Moving the polygon to each
vertex of the set of line segments, and connecting vertices
accordingly, will produced a polygon mesh which approximates the swept
surface.
Exercises
 Show how to convert a cylinder into a polygon mesh. What changes
do you have to make if the mesh may contain only
triangles?
 Show how to convert a torus into a polygon mesh.
 [1998/7/12] Show how to convert the swept object from Lecture 2B Exercise 1 into polygons. What extra
work would you need to do if you had to convert it into triangles?
 Show how to convert a sphere into a triangle mesh. How can you get
the most even distributiuon of triangle vertices across the
sphere?

Lecture 2 Index
...back to lecture 1
Part A: Conics, quadrics, and superquadrics
Part B: Generative models
Part C: Converting primitives to polygons
on to lecture 3...
Neil Dodgson 
Advanced Graphics 
Computer Laboratory
Source file: l2c.html
Page last updated on Mon Sep 7 12:47:51 BST 1998
by Neil Dodgson
(nad@cl.cam.ac.uk)