CG Lecture 4, Wed 2016-09-07

  1. Accessing RCS files from non-RPI computer

    1. FileZilla for Windows
  2. Common square.html problem:

    The location mentioned in src="../Common/webgl-utils.js" etc is wrong.

  3. Know-it-all points: Already two students have earned points for finding nontrivial errors.

  4. Homework 2 is online; due next Wed.

  5. Serpinski gasket programs showing more complicated WebGL.

  6. Extra material on colors

    1. Tetrachromacy

      Some women have 2 slightly different types of green cones in their retina. They see 4 primary colors.

    2. Metamers

      Different colors (either emitted or reflected) with quite different spectral distributions can appear perceptually identical. With reflected surfaces, this depends on what light is illuminating them. Two surfaces might appear identical under noon sunlight but quite different under incandescent lighting.

    3. CIE chromaticity diagram

      This maps spectral colors into a human perceptual coordinate system. Use it to determine what one color a mixture of colors will appear to be. The curve of pure spectral colors was determined experimentally.

      1. More info: .
      2. Purple is not a spectral color.
    4. Color video standards: NTSC, SECAM, etc

    5. My enrichment note on NTSC And Other TV Formats. NTSC, the American analog TV standard, is now getting obsolete. However it was a beautiful example of engineering design. First B&W TV was invented. Then color was added in a way that was upward compatible, downward compatible, and used no more bandwidth.

    6. Failed ideas: mechanical color TV. (enrichment).

    7. Additive vs subtractive colors.

    8. Sensitivity curves of the 3 types of cones vs wavelength.

    9. Material reflectivity vs wavelength.

    10. Incoming light intensity vs wavelength.

    11. Retina is a neural net - Mach band effect. When one cone is brightly lit, it inhibits its neighbors from firing so easily. This acts like a high frequency filter, to emphasize small details in the scene. Note: the details of how this works are uncertain.