Plan for today

• Review math questions
• Geometry
• Look ahead to next homework: a creative scene or object
• unprojection
• Next time: Material and Lighting

Documentation

How can you position your model in your scene? What is its bounding box? What is its reference point (origin)? How can you determine those?

Great Documentation that makes it easy for others to use the functions you defined. Think about how you might define your creative object. Documentation should probably include:

• origin
• orientation
• size
• colors
• other info?
• and maybe an example of usage. Minimum and maximum argument values, if any. Warnings and pre-conditions.

Geometry

Use some of the code in TW.py to do the math.

• vector dot product. Let's do some examples. We can use twDot()
• angle cosines. We can use twRadiansToDegrees().
• cross product. See twCrossProduct()
• why are we doing this?
• Consider the TW camera positioning code

Unprojection Demos

The key thing to know is that projection maps points to Normalized Device Coordinates (NDC), which is [-1,+1] on X and Y and [0,1] on Z, with 0 being the near plane and 1 being the far plane.

The pytw/TW.py routines are twProject and twUnProject.

• pytw/demos/camera/Click.py shows the idea of unprojection and how to do it.

Next time, Material and Lighting

• Ambient, Diffuse and Specular
• types of material
• types of lights
• OpenGL calls
• use the tutors!
• Challenge: when would we need the additional power of the OpenGL material API over the simplified TW material API?