The following is my progress writing a Raytracer in C++ using OpenGL to render.

Most of the time in the beginning is spent making vector, math, and matrix libraries.  This is for basic operations I’d have to use a lot, for example cross products and dot products.  Then I started with two shape classes, a plane and a sphere.  To simplify things, I used the sphere but left the plane out until I knew my rays sent from the camera were actually hitting anything.  So I sent about with a single sphere at the origin and put the camera back a few units in Z.  Then ran a hit test on each pixel from 0,0 (bottom left) to the top right of the image.

After several iterations I finally got an actual visual. Couple problems, first there is supposed to be only one sphere.  The other looks something like surface acne, which is usually caused my a floating or rounding error somewhere in the code.  In my case I had an int where I needed a float.

80% of the time I spent coding the raytracer was to get to this point.  Reminds me of the HAL 9000.  Now that I had the basics down, I needed to press on.  I made three light classes, a point, a spot, and a directional/parallel.  I found while debugging that directional lights were the easiest to use, so I put a few in the scene and would worry about composition and “good lighting” (using a key, fill, and back light) later.

Next I needed to create two shader classes, a diffuse and phong, which would handle the display of defused light, specularity, and reflectance across a surface.  The absense of a light source and a shader is why I only received yes/no results for my first successful hit test, and why the image looks like a circle not a sphere.

My latest render has a plane, four spheres, too much reflectivity, poor lighting, and some very awkward composition.  The spheres look a bit like Pokéballs.

I’ll post updates as I go, once I get something nice and cleanly written, I’ll take a stab at Physically Based Rendering.