CS 534                                             Spring 2006
                                                   E. Angel

Assignment 2: Display a Height Field with OpenGL Surfaces

I have put two sets of data in my file system under
~angel/public_html/CS534. Each contains height data
for over a rectangular mesh. Note that the scales are
not the same so you might want to rescale these data
as part of the assignment.

honolulu.raw: 465 x 436 elevation values for the Honolulu
area. The data are ASCII integers. The first two elements
in the file are 436 and 465, not elevation values.

nmtopo.raw: 1024 x 768 elevation values for northern New
Mexico. Same format as honolulu data with first two elements
of 768 and 1024.

Note: If the data does not display correctly, you may have
to swap rows and columns. I'm not sure of rows or columns
is first in these data sets.

The easiest way to display these data are by using four
adjacent data points to define either an OpenGL quad or
two OpenGL triangles. Actually, a better approach would
be to use the adjacent rows or columns of the data to
define triangle strips or quad strips.

The first part of the assignment is to write a program
to display these data sets using filled triangles or quads.
Note that you will have to worry about shading the
data set and adding at least one light (the "sun").

We should be able to get a smoother display using curved 
surfaces. For the second part, you are to use OpenGL's cubic Bezier 
surfaces to display the data. You should be able to use 
groups of 16 (4 x 4 subarrays) data points to define
each patch. Consider how to obtain the normals for shading.

Third, use the matrices that we discussed in class to 
generate interpolating and spline patches from the 
same data.

Compare the running time of the various options and
see if the improved quality of the surfaces is worth
the work.

Some fun things to try:

Try displaying the data as a mesh using line segments
or curves.

Display the data over the course of a day by moving the
sun's position. 

Make your program interactive and let the user fly around
the data set.

Color the data according to altitude, trying to capture 
features such as water vs land vs snow.

Find a corresponding topo map for one of the data sets
on the web and use that data set as a texture map. This
option will be tricky since you would have to worry about
differences in scale and geometry between the data sets,

Note that a lot of the code you may need is available 
under Book Support on my home page from either the textbook
or my OpenGL Primer.