CG Class 15, Tues 2017-10-10

2   Prof Radke talk on Nov 6

On Monday 2017-11-6, Prof Rich Radke will speak to the class while I am at ACM SIGSPATIAL .

He has written Computer Vision for Visual Effects.

3   Textbook Slides

We'll continue with the textbook powerpoint slides.

The big topic for Chapter 5 is homogeneous coordinates. They allow all the common transformations - translation, rotation, scaling, projection - to be expressed as a multiplication by a 4x4 matrix.

We doo the chapter 5 slides really quickly.

  1. 5_2 Homogeneous coordinates

    My take on homogeneous coordinates.

  2. 5_3 Transformations.

  3. 5_4 WebGL transformations

  4. 5_5 Applying transfomations

  5. WebGL Transformations Angel_UNM_14_5_4.ppt 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.

  6. 6_1 Building Models.

    Big idea: separate the geometry from the topology.

  7. The Rotating Square.

    Big idea: render by elements.

  8. 6_3 Classical Viewing.

    Big ideas: parallel (orthographic) and perspective projections. The fine distinctions between subclasses of projections are IMO obsolete.

4   Angel programs - Chapter 5

Chapter 5

  1. hata shows:
    1. Using a modelview matrix set by lookat and a projection matrix set by ortho
    2. Drawing a mesh with line strips.
  2. hat shows:
    1. Drawing the same points both as a triangle fan and as a line loop.
    2. Setting options to make the lines slightly in front of the triangles.
    3. Doc for depthfunc.
    4. Doc for polygonoffset.
  3. ortho1 and ortho2 show clipping with an interactive orthographic (parallel) projection.
  4. perspective1 and 2 show an interactive perspective projection.
  5. shadow shows a shadow.
  6. Notes about the computer programs:
    1. The point is not to teach javascript; it's just the vehicle. Before javascript, I taught C++. Javascript is easier.
    2. One point is to teach a widely used API, i.e., WebGL.
    3. Another point is to teach graphics concepts like projection and viewing, and their APIs, like lookAt.
    4. These concepts will exist in any graphics API.