Ray Tracing

Based on the book Ray Tracing in One Weekend
For the theory behind the renders and example code, see the link above.

Pretty Renders I've Made

• The first render output, in a .ppm file
  • .ppm files store RGB values that go from left to right, top to bottom
  • This image has a constant blue value, red increases from left-right, green decreases from top-bottom
    
• A simple gradient
  • By ray-tracing, we can pick a value for each pixel by getting the y-component of the direction vector of the ray
  • We can colour this with more "blue" the higher up the ray points
    
• A circle (a sphere?)
  • We can render objects on the screen too by adding objects to the 3D environment
  • If we add a sphere to the environment, we can change the colour of pixels depending on if the ray intersects with the 3D object
  • We can also add an outline by checking if the intersection is near the edge
  • The result is a circle that represents a sphere
• Normals colouring
  • We can give this sphere a bit more character by colouring it
  • One approach is to map the normal vector at the point of collision between the ray and the sphere's surface to a colour
    
• More spheres
  • We can abstract the sphere object and render more spheres
  • Here's 3 spheres on top of a big sphere:
• Anti-Aliasing
  • We can fix the jagged edges of the sphere by tracing more rays per pixel
  • We pick points within the subpixel and average them together to generate anti-aliased edges
• Diffuse materials
  • We can model light bounces from our spheres to simulate light in real life
  • For diffuse materials, light bounces randomly with a probability distribution, generating a "matte" look
  • We simulate multiple light bounces per pixel and average them out to get this:
  • Gamma correction can be applied to correct the overly dark spheres:
  • We can also use different probability distributions to model light bounces
  • Heres a lambertian reflectance sphere:
    • Note: At this point a slight error is made in my renders where the co-ordinate system of the shadows is slightly off, leading to left-skewing shadows
      • This is fixed later on
• Metals
  • Metals reflect light in a more direct way, we can trace these reflected rays to get metals now
    
  • We can also make metals that aren't fully reflective by only reflecting rays directly some of the time, and reflecting them randomly other times
• Glass
  • We can use light refraction properties to generate spheres that exhibit glass-like behaviour too
  • We can also render hollow spheres: