CS452 -- Computer Graphics

Jian Huang

Lab2

In this lab, the goal is to practice basic GLSL programming by implementing basic lighting and, for graduates, basic texture mapping. You should build upon the code from Lab1's last step.

Lab2 has the following steps. As with all other programming tasks, please proceed incrementally.

For the lighting portion of the lab assignment, please use a single point light source located at the same location as where the camera is. When specifying material properties, feel free to use values from the following table or create your own:

  
 
 Step0: You should have a scene of rotating cubes in a solar system, the last step of the previous lab.
      Replace the cube model with the sphere model, erase the other planets. At the moment, the scene should consist of 
      a single sphere and controllable camera. The OBJ loader is capable of pulling normal values from the sphere obj i
      file (not the cube or bunny, we will get there later). Create a new shader using your preferred shader 
      version (1.0 or ES 3.0), see the shader directory in the resources folder for examples. Be able to pass the model's 
      vertex normal values as an attribute to your vertex shader. The vertex shader should output the normalized 
      vertex normal as vec3. The fragment shader should take this vec3 output value and set the the fragment color 
      equal to the absolute value of this output. At the end of this step you should have a single, rainbow colored sphere.  
    
 Step1: The current sphere model is the only model (distributed with the starter code) that will work with this new shader.
      We need to add support for the bunny model.
      Compare the bunny obj file to the sphere obj file, you will see the bunny obj file only provides vertex positions.
      The Sphere obj file provides vertex positions and vertex normals.
      Your job in this step is to calculate vertex normals for obj files that do not have vertex normals included.
      In OBJ-Loader.js, `getFlattenedDataFromModelAtIndex(index)` and `getIndexableDataFromModelAtIndex(index)` are responsible 
      for processing the obj data read. In these functions you can add the necessary code to calculate normals.
      Do this, and test with the bunny obj.

      Note, the cube obj you hand crafted previously may not work well with this shader - don't try getting it to work, 
      but do you know why it won't? Hint: If your cube has 8 vertices, you may need to bump up to 24 :)
      At the end of this step, you should have a single, rainbow colored bunny.  
    
 Step2: implement full Gouraud shading in a new shader program. Going forward, feel free to use any obj file that 
      you can load.  
    
 Step3: implement full Phong shading in a new shader program.  
    
 Step4: implement a special effect in our fragment shader based on Step3 - to linearly modulate the red component of 
      fragment color according to height (y component of gl_Position), so that the bottom of the screen or the bottom of the model 
      in screen space has zero red component and the top of the model has full red component.  
    
 Step5: (extra credit for 452, required for 594) implement an effect similar as Step4 requirements, but do this 
      through texture mapping. There are two parts: (1) a function to create an RGB 2D texture (8 x 8) that stores a linear 
      ramp from 0 to 255 in two directions (use the same values on all components), and (2) when rendering, multiply the fragment 
      color, as done in Step4, by the texture value looked up from the texture using the y and z components of each fragment. 
      The end results should be a height-based and depth-based attenuation effect.