The year I learned to write C code I was 19, second year of university and already willing to drop out, so I started spending time with C and 3D graphics. I was just fresh of the math exam so the 3D matrix transformations to do rotations was trivial to implement. I just wrote a function to draw triangles, used a simple z-sorting technique, and the basic shading calculating the cosine of the angle between the observer and the surface. With just these basic things I ended up with 3D "worlds" similar to the ones I saw in DOS games when I was a child. All the effort was maybe 500 or 1000 lines of code, but to build things from scratch, only starting from the ability to draw an RGB pixel, gave me a sense of accomplishment that later shaped everything else I did. I basically continued for the next 20 years to create things from scratch.
My first year university Linear Algebra textbook even had an appendix explaining how to rotate and skew 3D objects in computer graphics using the matrix multiplication I had learned that semester. I loved it.
Then I finished university and got a programming job creating forms to gather user data, put it into a database, and generate reports. Sigh.
I've the feeling that unfortunately most programming jobs, even in shiny startups, are more like data forms than 3D engines... That's why many programmers have OSS side projects where they do cool things.
I did something very similar at a slightly early age, and I still have the code. So I've decided to put it on github. The last-modified-date on these files is 1996.
I had forget about this but at my first year and while the algebra professor was drawing 3D vectors to explain the lecture, I was thinking "that is a 2D surface, so there should be a linear transformation between the two worlds".
Later at home, I've found such space transformation and built a small 3D world that you can walk, using only vectors and plain triangles :)
It is also worth noting that today's CPUs are faster than 3D graphics chips from 20 years ago, so it seems perfectly reasonable to expect a good performance from a basic hand-written 3D rendering library.
