CSE 160 -- Prog 2

Due before midnight, Sunday, April 25, 2021.
Late submissions will not be accepted/graded.

Objectives:

Description:

Details:

• Lighting:
  • Normals: To do flat shading or smooth shading (in future programs), you will need normals. For flat shading, you will need a polygon normal for each polygon that needs to be rendered. Since our simplified OBJ file format already has a list of polygons, and we just need one normal vector per polygon, it's convenient to simply extend the polygon info to include the normal (in addition to the sequence of vertex indices). You can create your cylinder model as before, and then create a parallel array to your polygon list that will contain the corresponding normal vector for each polygon. This is also where you might discover that your implementation in the previous program has any flaws e.g. vertices are CW instead of CCW, or vertices don't form a proper triangle, etc.
  • Light: The other component needed for shading is a light source. For this program, you have a single white light source. To simplify things, we'll make this be a directional light source from [1,1,1].
  • Shading: We will assume that surfaces are lambertian and we consider only the diffuse component. This dictates how the observed light is calculated based on the light information (direction and color), the relationship of the light vector and the surface normal (varies for each polygon), and the color of the polygon. We will assume that all the polygons of each cylinder instance has the same color. However, different instances may have different colors. These polygon colors are referred to as material properties. Again, we'll only specify the diffuse components.
  • Rendering: Add a button to switch between wireframe and flat shading. For now, you can use a toggle button. You will need to select additional rendering style e.g. smooth shading in later programs.
• Transformation:
  • Cylinder Instance: Each cylinder can have its own color, and can be reshaped, oriented, and placed differently in the scene. Therefore, while all cylinders share the same "unit cylinder" coord and polygon list, and normal vector list, each instance will have to remember what's unique about them -- (a) diffuse material property or simply the color of the cylinder, and (b) the sequence of transformation applied to it. For example, if your scene is made up of 10 cylinders, you will have ONE "unit cylinder" model, and 10 customizations of the unit cylinder.
  • Object Transformation: Apply a series of transformations to each instance of your cylinder. These transformations can be a comination of translation, rotation, and scaling.
  • User Interface: You can use a combination of keyboard and/or sliders and buttons as graphical user interface for creating cylinder instances, and applying transformations to each instance. For example, you can add a selection button for each new instance created e.g. by pressing the "N" key on your keyboard. You can then turn on one or more buttons to specify which instances you want to transform. The parameters for the different transformations could be done with a bunch of sliders. This is where having a good features.html file that describes the user interface is important for the graders to see the full extent of your code's functionalities. You could have a separate user's guide for this if you wish.
  • Normal Transformation: When an object gets transformed, the polygon normals will also change. However, instead of having to recalculate the surface normals using the transformed vertices, you can simply transform the polygon normals. The transformation of normals is similar to the transformation of vertices. Both are based on the composite transformation matrix. Details will be described in class.
• Your 3D World: At a minimum, your 3D scene should have at least 2 cylinders such as the mallet shown below. If you like lots of mallets, you can create a mallet object made up of cylinders and instantiate mallets also. We will have our first peer-judged contest with this program. The contest will be on creativity for the 3D world that you create -- and not really on the visual effects since we will be learning those in subsequent programs.

  Do consider joining the contest by informing our graders (through the README file that you submit) of your intent to join. This also counts towards participation/attendance scores. Note that since judging is amongst your peers, by joining, you implicitly allow your peers to look at your implementation.

Resources:

• Directional lighting tutorial
• How to create a toggle button, or a checkbox
• How to create a slider
• Detecting keyboard and mouse events
• The followind examples from the Matsuda Lea book are relevant to this assignment:
  • OrthoView for how to set up an orthographic view, and
  • ColoredCube for how to fill in a polygon with a single color,
  • LightedCube for how to do lighting calculations.
  • How to pick an object -- if you prefer direct manipulation

Grading:

• Rubric:

  You start off with 100 points.
  You lose credit for missing functionality, incorrect results,
  poorly documented or formatted code, or not following instructions.
  
  Below is a partial list:
  
  - up to 10 points off for poor features.html file
  - up to 10 points off for inadequate comments or hard-to-read code
  - up to 10 points off for not following instructions
  - up to 10 points off for special handling to grade your homework (usually
    because you did not check that it runs on the computers in the lab first).
  - functionality points depending on importance
  
  Make sure you:
  a.  submit the right files you want us to grade,
  b.  have tested your code on the browsers in the lab.
  c.  follow the general instructions described in overview.html
  
  

• Who graded your assignment:

  Nicholas Tee: ntee@ucsc.edu
  

Submission:

Put materials in a folder named prog2 and zip it up.
Read the for instructions on how to submit your work.