\( \newcommand{\vecIII}[3]{\left[\begin{array}{c} #1\\#2\\#3 \end{array}\right]} \newcommand{\vecIV}[4]{\left[\begin{array}{c} #1\\#2\\#3\\#4 \end{array}\right]} \newcommand{\Choose}[2]{ { { #1 }\choose{ #2 } } } \newcommand{\vecII}[2]{\left[\begin{array}{c} #1\\#2 \end{array}\right]} \newcommand{\vecIII}[3]{\left[\begin{array}{c} #1\\#2\\#3 \end{array}\right]} \newcommand{\vecIV}[4]{\left[\begin{array}{c} #1\\#2\\#3\\#4 \end{array}\right]} \newcommand{\matIIxII}[4]{\left[ \begin{array}{cc} #1 & #2 \\ #3 & #4 \end{array}\right]} \newcommand{\matIIIxIII}[9]{\left[ \begin{array}{ccc} #1 & #2 & #3 \\ #4 & #5 & #6 \\ #7 & #8 & #9 \end{array}\right]} \)

Quiz

  1. Why do we need a normal vector when we define a face?

    When we start having material interact with light, it will be important to know the orientation of the face. For flat faces, it can be computed from the vertices, but for curved faces, it might be different.

    Meanwhile, we can also have a demo mesh where the colors are based on the normal vector.

  2. How is the mesh created when we use the createMesh() function?

    We can look at the code! tw.js

  3. Is there an argument/easy way to specify in three.js whether we want to use the default one-sided rendering or the two-sided rendering?

    To save time, we can decide to only render one face. We could have a ball, modelled as a 100-faceted thing, and only want to draw the outside faces.

  4. I dont completely understand why the ordering (clockwise vs counter clockwise) matters in the barn example with the vertices

    Same idea.

  5. why do we say .push when adding vertices or faces? What does that do/mean?

    We're adding to the end of a list of vertices or faces, and so push is a common term for adding onto the end of a list.

  6. What does a buffer do to make things easier?

    It's just a storage area (memory).

  7. I am curious to know more about the process of rendering. Is my understanding that rendering is the conversion of Three.is geometry into pixels correct?

    Yes, that's right.

  8. I'm a little confused about the rendering process. Is there an explicit function/method for rendering the scene, or is it done automatically when the renderer is created (alternatively, when TW.mainInit() is called or when the camera is set up)?

    Yes, deep in the bowels of Three.js, is a place where the rendering really happens. We'll be a little more explicit about it later in the course, when we get to animation, but it's mostly automatic, as part of the orbiting camera.

  9. Can we express Einstein's blackhole dealing with time as the 4th dimension in the 3-d OpenGL space?

    In CG, the fourth dimension is not time; it's another spatial dimension!

    We will be treating time differently from space, and we won't be dealing with relativity. But maybe in your project, you could....