Interactive 3D Worksheet

Go to Fr. Chris' web site (either surf.to/frchris or www.ktb.net/~cct or www.geocities.com/CapeCanaveral/Lab/8972) and select the lesson "Interactive 3D"

Changing the 3D Object

1. Wait for the page to load, and see if you can rotate the cube by clicking and draging it up, down and around.

2. Press the different buttons to see the other shapes.

3. Press the cube shape again. To change the cube a little, we can change the 3D Object Code. (The syntax of the Object code is adapted from the Wavefront .obj format) Each line starts with a letter followed by some numbers. Every object must have vertices (corners, if you will), which are later grouped as a face of the obect or as a simple link between two vertices.
   change the third line (which is vertex 3) which originally reads "v 1 1 0" . This means there is a vertex where the x cordinate is 1, the y co-ord is 1 and the z (depth) co-ord is 0. Change the y coordinate to be 1.5 (In other words change the third line to read"v 1 1.5 0"
   instead). Then type the "Redraw" button to see how it changes the shape.

4. Now go to the last line and construct a new line on the object by adding "l 4 7"(the first character is a lower case "L") at the end of the source code.

5. Again press the "Redraw" button to see what happens (this last step causes a line to be drawn between the fourth and the seventh vertex that was defined).

Making a New 3D Object

1. Say you want a vertex at the three dimensional point (0, 0, 0). Simply type a line in the Object Code starting with a "v" followed by the three numbers, separated by spaces:

   v 0 0 0

   These vertices are refered to later by the order which you created them, the first vertex is 1, the second is 2, and so on. Let's add a few more:

   v 1 0 1
   v 1 1 0
   v 0 1 1
   

   To construct a face on your 3D Object, connect any number of vertices by typing a new line in the Object Code starting with a "f" (for face) followed by the numbers representing the vertices (again, each number is separated by a space).

   For example, to make a triangular face from the first three vertices you made, type a new line:

   f 1 2 3

   This connects the first three vertices together.

   To make a simple line from one vertex to another, use the letter "l" to link a pair of vertices. For example, to draw a line between 1 to 4, 2 to 4 and 3 to 4:

   l 1 4
   l 2 4
   l 3 4

2. What did you construct?

3. Now you can try constructing your own 3D Shape. In later workshops, we will learn how to add these shapes to your web pages, and still later find out the nitty-gritty geometry so you will write your own code that will spin or rotate or generate 3D Stereoscopic images of these objects. Make the object interesting, yet not too complex (at least at first!).

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   Here is an hat by one student, John Peters
   Here is a desk...

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   Click here to see students' work 2005