CG Class 20, Thurs 2017-10-19

1   IOCCC programs

local copy of some of them.

Fun examples of what you can do in a few lines of code.

2   Comments on recent powerpoint slides

1. I didn't show WebGL Transformations Angel_UNM_14_5_4.ppt in detail since it is mostly obsolete.
   1. The old OpenGL modelview and projection matrix idea is now deprecated, but is interesting for its subdivision of transformations into two functions.
   2. The modelview matrix moves the world so that the camera is where you want it, relative to the objects. Unless you did a scale, the transformation is rigid - it preserves distances (and therefore also angles).
   3. The projection matrix view-normalizes the world to effect your desired projection and clipping. For a perspective projection, it does not preserve distances or angles, but does preserve straight lines.

3   Finish my note on homogeneous coordinates and projection

My take on homogeneous coordinates.

4   More Chapter 6 slides

1. 6_4 Computer Viewing: Positioning the Camera.

2. 6_5 Computer Viewing: Projection.

   Big idea: view normalization. We'll see this more in chapter 7.

5   Chapter 7 slides

1. 7_1 Orthogonal projection matrices.

   Big idea: Given any orthogonal projection and clip volume, we transform the object so that we can view the new object with projection (x,y,z) -> (x,y,0) and clip volume (-1,-1,-1) to (1,1,1) and get the same image. That's a normalization transformation'. See slide 14.

2. 7_2 Perspective projection matrices and the normalization transformation.

   Big idea: We can do the same with perspective projections. The objects are distorted like in a fun house. See slide 8.