CSE 160 -- Prog 3

Due before midnight, Sunday, May 09, 2021.
Late submissions will not be accepted/graded.

Objectives:

Description:

Details:

• Smooth Shading:
  • As you should already have wireframe and flat (or constant) shading from earlier programs, the new part here is smooth shading. There are two types of smooth shading: Gouraud or Phong shading.
  • Gouraud: Gouraud shading creates smooth shading by interpolating colors at vertices. This means that you need to do lighting calculations on a per vertex basis compared to a per polygon basis that you did in prog2. This also means that you will need a normal per vertex rather than per polgyon. Vertex normals are simply the sum of the polygon normals that share that vertex. Once the vertex color is determined, the fragment shader can take over to interpolate the colors within each polygon. To recap, lighting calculations for each vertex are done in the vertex shader, while color interpolation is done in the fragment shader.
  • Phong: Phong shading creates smooth shading by performing lighting calculations for each point within each polygon. It does so by interpolating the vertex normals to find a normal for each point. Lighting calculations is then done based on the interpolated normal. To do Phone shading, you will want the fragment shader to interpolate the vertex normals and do the lighting calculations. To recap, vertex interpolation and lighting calculations are done in the fragment shader.
• Lighting Effects:
  • In the previous programming assignment, you implemented lighting for lambertian surfaces to produce diffuse lighting effects. You will add two more effects: ambient and specular lighting.
  • Ambient lighting: Ambient lighting tries to capture ``multi-scattering'' of light and tries to produce a softer look. It's simply an additional term that's added to the lighting on the surface. This extra term is a simple product of the light source(s) and the material's coefficient for ambient lighting.
  • Specular lighting: This creates the appearance of shiny surface objects by creating areas of ``highlights'' on the surface. This effect takes into account the view vector whereas diffuse lambertian lighting only depends on the orientation of objects with respect to light source. Refer to class notes and/or textbook for how to calculate the specular lighting component.
• Light sources:
  • There will be two light sources in your scene that you can individually turn on and off.
  • Directional light: This is the same light source from prog2. You just need to add a toggle to turn it on and off. When both light sources are off, only ambient component is visible.
  • Point light: Assume you have another light source at location L:(-100,100,100) and has a warm orange color (1.0, 0.8, 0.2). This second light source is a point light source since it's at some finite position in the scene rather than at infinity (directional light source). Add a toggle to turn this light source on and off. When both light sources are off, only ambient component is visible.

    Having a point light source will affect the light vector. With directional light sources, you have the same light vector for all the lighting calculations. With point light sources, you will need to find the light vector between (a) a point on the surface and the point light when doing Phong shading, (b) a vertex and the point light when doing Gouraud shading, and (c) center of the polygon and the point light when doing flat shading.

    Introduce another geometry in addition to the cylinder. Use the sphere model from chapter 8 of Matsuda and Lea. The sphere will be used to represent the position of the point light. Size the sphere so that it's visible in your world. Allow the user to move the sphere around. You should see the effect of point lighting in the scene.

Resources:

• Point lighting tutorial, and PointLightedCube for how to do point lighting calculations.
• Gouraud shading example with point lighting.
• Phong shading example.
• Specular lighting.

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, or inadequate comments or bad code
  - up to 10 points off for not following instructions or needing special handling to
    grade your homework.
  - functionality points depending on importance (remaining 80 points)
  
  For this program, building upon your previous assignment (i.e. you can create an
  object with at least 2 cylinders), new functionality requirements are:
  - Light sources: (25 points)
      directional lighting: 10
      point light source:   10
      combined:              5	need toggle to turn on/off different light sources
  - Light effects: (25 points)
      ambient:	5
      diffuse:	5
      specular:  10
      combined:	5	need toggle to turn on/off different light effects
      * ambient is independent of light source(s)
      * to check specular, need to modify gloss factor and either light(s) or viewer
  	(can skip test on latter for now)
  - Shading:       (30 points)
      wireframe:		5
      flat:		5
      gouraud/phong:	15	(pick one, or both)
      combined:		5	need toggle to turn on/off different shading effects
      * incorrect vertex normals will affect more than 1 shading option
  
  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 prog3 and zip it up.
Read the for instructions on how to submit your work.