CS 184: COMPUTER GRAPHICS

Lecture #15 -- Mo: 3/15, 1999.

PREVIOUS < - - - - > CS 184 HOME < - - - - > CURRENT < - - - - > NEXT

Preparation:

Read:  Ch 6.1 "Projections"; Ch. 3.6 "Filling Polygons", Ch. 19.2.8 "Filled Primitives",  Ch. 18.3.8 "Rasterization"

Lecture Topics

Review of:

Vanishing Points and Vanishing Lines

n-Point Perspectives

(see additional notes added to the web page since last lecture)
 

Classifications of Projections

Study Chapter 6.1 and Figure 6.13 !

Parallel
   Orthographic (plan-view, elevation, isometric)
   Oblique (cabinet, cavalier)
Perspective (n-point perspective)
 

Polygon Filling, Rasterization

Conceptually: just paint in all the pixesl that are inside the contour ...
BUT: What is "inside" ? -- How do we determine this quickly ?
==> Inside/outside tests based on Winding Number.

What do we do with pixels falling "on the edge (contour)" ?
This causes ambiguities, and competitive conflicts ... -- we need a clean solution !
==> The Sampling Paradigm.

A pictorial description of the requirements for a proper scan conversion algorithm.

Look at section 5 of the notes on scan conversion for more explicit examples of rasterization.

Run this Java applet that demonstrates scan conversion.
-- Which type of inside/outside testing does it employ ?

Now we want to implement a rasterization algorithm in an efficient manner.
Several algorithms are used in praxis. One is based on "flood-filling".
We will study and implement an algorithm based on a sweeping scan-line.
 


New Homework Assignment:

ASG#7:  "Scan Conversion"
DUE: Thursday 4/1/99, 11:59pm.
CAN BE DONE WITH YOUR PARTNER OF CHOICE !


--> Next Lecture

<-- Up to CS 184 HomePage


Page Editor: Carlo H. Séquin