File: sept11.txt
Contents: plan/notes from the day

For next time - triangle ray tracing, graphics pipeline.

hw4 questions/discussion
- project ideas people found?
- so far, leading suggestion is the rubic's cube solver/simulation

exam next week - sample test over the weekend

From last time - shadow rounding errors?

This time...
* Example with ray tracing
  + radius 1 spheres at: (0,0,0) red, (1, 2, -3) blue, (-2, 0, -3) green
  + eye is at (0,0,5)
  + projection screen at z=3, 60 degree vertical field of view total
  + LCD is 1920 x 1080
  + pixel (800 over, 500 up)
  + y_screen = 500.
  + y_screen -> (5/sqrt(3)) * (yscreen - 540) / 540
  + y_screen = 500 -> -.231
  + x_screen -> (16*5/(9*sqrt(3)))*(xscreen - 960)/960
  + xscreen = 800 -> -.321

  * conclusion...
  * don't use simplified formula from notes...
  * would probably hit the (0,0,0) circle (but go ahead and work it out...)

* Pseudocode for ray-tracer (will turn into real code)

tValue rayTraceSphere(material properties of sphere,
                      cX, cY, cZ, radius, // where is the sphere
       	              pX, pY // pixel on the screen we want
                      eX, eY, eZ, // eye coordinates
                      zz, // where is projection screen
		      fov, // field of view
                      pXMax, pYMax
                     ) {
  // convert pixel to coordinates on the projection screen

  // scaling of pixel coordinates to projection screen coordinates

  // viewing ray - r(t) = p + t * d

  // intersection equation with viewing ray and sphere

  // that gives t value(s) where intersection happens

  // if imaginary, then no intersection.
  
}


rayTraceTriangle() {
  // next time...
}

rayTraceScene() {
  zBuffer = one number per pixel on the screen, what is the 
            closest object at that pixel so far
  colorBuffer = RGB for each pixel

  for each pixel on the screen pX, pY {
    for each object in the world {
      t = rayTraceSphere(....)
      if this sphere closer than previous closest {
        update the zBuffer
        put color into that pixel.
      }
    }
  }
}