Assignment 2
CMSC 740, Spring 2006
Due: 2:00pm Tuesday, February 28, 2006
This assignment involves familiarization with OpenGL texturing and lighting, as well as simple
animation. The assignment web-page is at www.cs.umd.edu/class/spring2006/cmsc740/assg2/.
For this assignment, you should make the following extensions to your program from
assignment 1.
● Keyboard control: Allow the user to move the viewer’s position with the keyboard. Keys
w/s should move the viewer forward/backward, a/d should move left/right, and e/c
should move up/down.
(2 points)
● Texturing: We are providing you two bmp files, Grass.bmp and Sky.bmp. You may use
these as textures, or generate your own. Map the grass texture to your terrain, with texture
coordinates u and v each ranging from 0...1 from one end of the terrain to the other. For the
sky, generate a large cube that encloses the entire scene (viewer and geometry) and map the
sky texture to each face of the cube.
(3 points)
● Lighting: Light your scene using ambient lighting and a directional light. This will require
you to specify normals for the vertices of your terrain. You can approximate the normal at
each vertex by computing two approximate tangent vectors to the vertex and taking their
cross product. The tangent vectors can be computed from the heights of the four adjacent
vertices (you will need to special case the edge and corner vertices).
The directional lighting should not affect the sky box. You should glDisable the
directional light before rendering the sky box, and glEnable it again before rendering the
terrain.
(4 points)
● Animation: Make the sun rise and set. Render the sun as a yellow gluSphere floating
over your terrain. To make the sun continuously rotate around the terrain, use
glutIdleFunc to register an idle callback function – OpenGL will repeatedly call this
function when it does not need to perform any other tasks. Each time this function is called,
it should compute the amount of time since it was last called (for example, by using
glutGet(GLUT_ELAPSED_TIME), and increment a variable representing the sun’s
angle of rotation by a corresponding amount. This angle should be passed into a glRotate
call in your draw function.
As the sun rotates, you should also change the direction of the directional light so that it
appears to be coming from the sun. As the sun gets close to setting, the light intensity should
gradually dim out, and gradually fade back in again as the sun rises. You should make the
sky box change brightness as well, either by using an ambient light, or by directly altering its
vertex colors.
(6 points) (Total: 15 points)
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