CG Class 5, Thu 2018-09-13

W Randolph Franklin, RPI

Table of contents

1 How to print info from inside your javascript program

There are several ways; here is the easiest.
Reference: http://www.w3schools.com/js/js_output.asp
Examples to do inside square.js:
1. window.alert('this is an alert');
2. window.alert('vertices length: ' + vertices.length + ' 1: ' + vertices[1]);
Note that you can write variable values as well as strings.
Another way is to write to the console log thus:

console.log('this is a log message');
In firefox, you can display the log window with F12.
An advantage of the log is that you see all the messages together.
I'll demo these methods.

For today's demo program, I'll modify triangle to add a slider that controls the amount of green to add to the triangle color.

The amount of green will be read from a slider.
Scrounge your slider code from gasket5.
The value will be transmitted to the fragment shader in a uniform variable.
Scrounge around in Angel's examples to see how to use a uniform variable. (I grepped for 'uniform').

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: http://wikipedia.org/wiki/CIE_xyY .
2. Purple is not a spectral color.
Color video standards: NTSC, SECAM, etc
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.
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.

We'll continue with the textbook powerpoint slides.

SIGGRAPH is the world's leading CG conference. I'll show various videos from it.

I'm replacing the Angel lecture at Incremental and Quaternion Rotation, with my own material. Feel free to read ahead.