UPDATES.txt

Updates?
--------

Many people find their way to Giles Thomas' "Learning WebGL Lessons" when first trying to get
experience using that technology. His sixteen lessons were written between October 2009 and
December 2010, and they rely on glMatrix-0.9.5.min.js. That library is at version 2.2.1 as of this
writing (6 July 2014). See the well-organized glMatrix website at http://glmatrix.net/

You'll learn a lot by going through "Learning WebGL Lessons".

You might think you'd learn something by updating the lessons to work with the current version
of glMatrix, but, in all honesty, you won't.

I've done it. I doubt I'm the first.

Here's an outline of the necessary changes.

* the functionality of mat4.set(mvMatrix, copy) has been replaced with mat4.copy(copy, mvMatrix).

* mat4.toInverseMat3(mvMatrix, normalMatrix) and mat3.transpose(normalMatrix) have been combined
  into a single method in the mat3 class, mat3.normalFromMat4().

* the API of mat4.perspective() has been rearranged so that

    mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);

  becomes

    mat4.perspective(pMatrix, 45.0, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0);

* the API for a number of relevant methods now take as arguments the matrix (or vector) to be
  acted upon and the matrix (or vector) to receive the action. These include mat4.translate(),
  mat4.rotate(), and mat4.multiply(), and the update is simply to change, for example,

    mat4.translate(mvMatrix, [0.0, 0.0, z]);

  to

    mat4.translate (mvMatrix, mvMatrix, [0.0, 0.0, z]);

* the parameters in the API for vec3.normalize() and vec3.scale() have been reversed, so that

    vec3.normalize(lightingDirection, adjustedLD);
    vec3.scale(adjustedLD, -1);

  becomes

    vec3.normalize(adjustedLD, lightingDirection);
    vec3.scale(adjustedLD, adjustedLD, -1);


I've also changed the values of z, zoom, or zPos (and, when present, the DOM element, "lightPositionZ")
to approximate the scene size in the original tutorial, added semicolons when flagged by my IDE, removed
commas at ends of arrays (this is JavaScript, not Python), and replaced a few occurrences of "= Array()"
with "= []". I've tried to flag all my changes with "// Update: ...".

Hoping this saves a lot of people a lot of time.

Eric Theise / @erictheise