The Two Most Common Graphics Algorithms

Z-buffer projection rendering

This is the most commonly-used algorithm, often accelerated with dedicated hardware. The OpenGL graphics library is based on this algorithm.

for each polygon in model
  project vertices of polygon onto viewing plane
  for each pixel inside the projected polygon
    calculate pixel colour
    calculate pixel z-value
    compare pixel z-value to value stored for pixel in z-buffer
    if pixel is closer, draw it in frame-buffer and z-buffer
  end
end

Ray Tracing

for each pixel on screen
  determine ray from eye through pixel
  find closest intersection of ray with an object
  cast off reflected and refracted ray, recursively
  calculate pixel colour, draw pixel
end