Project 1: Visualization and Flow Modeling on Grid Terrains

In this project you will create a tool for visualization and basic flow modeling of grid terrains. The required functionality is to visualize a grid (2D or 3D) and compute flow direction and flow accumulation of a grid.

Visualization: Your program should be able to read an ascii grid and render it in a 2D or 3D view. The color of each point should be a function of the elevation of the point. You will need to write a colormap function to map an elevation range into a color range. Essentially you will need to divide the grid elevation range into a number of buckets and assign a color to each bucket. The number of buckets will be a fixed constant of your choice (for e.g. between 5 and 10). You need to implement more than one color map (e.g. grayscale, rainbow gradient, etc). Below are some examples of grids rendered in 3D. If you chose to render in 3D, essentially you will need to add the third coordinate to your vertices (use glVertex3f() instead of glVertex2f()) and change the default orthographic projection to a perspective projection (use glPerspective() or glFrustrum()). Choose the initial viewpoint so that it does not show a blank screen.


If invoked with a second grid as argument, the display function should display the second grid (the color grid) draped on top of the first grid (the surface grid). This functionality is useful for viewing terrain attributes like flow direction and flow accumulation draped on top of the elevation. Here is an example of flow accumulation of a terrain drawn on top of the elevation:


The display method should have the following features:
• Translations and rotations: Allow for rotations and translations around the axes. Use standard keys or even better, the arrow keys.
• Resolution [this is for extra credit]: In order to handle larger grids fast provide the option to increase and decrease grid resolution for visualization. Set the the initial resolution such that the initial rendering is always fast.
• Color maps: Implement at least two color maps and allow the user to chose between them. Here is an example of rendering an elevation grid in 2D with various color tables:

  

• Menu: Include a menu that allows to:
  • toggle between drawing the polygons in the scene filled or contour only
  • select a color map
  • quit
• Scaling: Allow for the terrain to grow/shrink on the z-axis.
• Animation: Include a simple animation of the terrain. For instance, a rotation around one of the axis. Ideally all other features (translation/rotations/resolution, scaling) will be available during the animation.
• Flow direction (FD): The FD routine should take as input an elevation grid and compute SFD or all cells in the grid which have downslope neighbors. SFD means that FD points to the stepeest downslope neighbor; if there is more than one stepeest downslope neighbor pick one (at random). If all neighbors of a cell have same height or are upslope assign FD=0.
  
• Flow accumulation (FA): The FA routine should take as input a direction grid and compute a FA grid. Assume that initially every cell in the terrain has 1 unit of water, and that every cell distributes its water (initial, as well as incoming), to the neighbor pointed to by its flow direction.
  

The interface is open-ended, but ideally the user would be able to perform any combination of these commands on any grid dataset. For instance:

dover: > mygis
..Starting MyGIS program.
mygis> help
..Usage:
display surf=<grid-name> [col=<grid-name>]
computeFD elev=< grid-name> dir=<grid-name>
computeFA dir=< grid-name> accu=<grid-name>
help
exit
mygis> display
..usage: display surf=<grid-name> [col=<grid-name>]
mygis> display surf=set1.asc
..Displaying set1.asc
mygis> display surf=kaweah.asc
..Displaying kaweah.asc
mygis> computeFD elev=kaweah.asc dir=kaweahFD.asc
..Computing FD for kaweah.asc
mygis> display surf=kaweahFD.asc
..Displaying kaweahFD.asc
mygis> display surf=kaweah.asc col=kaweahFD.asc
..Displaying kaweahFD.asc draped over kaweah.asc
mygis> computeFA dir=kaweahFD.asc accu=kaweahFA.asc
...Computing FA for kaweah.asc
mygis> display surf=kaweah.asc col=kaweahFA.asc
..Displaying kaweahFA.asc draped over kaweah.asc
mygis> display surf=kaweahFD.asc col=kaweah.asc
..Displaying kaweah.asc draped over kaweahFD.asc
mygis> display surf=sierra.asc
..Displaying sierra.asc
mygis> exit
..Exiting. Bye.
dover: