It took me 10 minutes to do the whole computation by hand, so I wouldn't say it's a LOT of work. At the same time I believe this is also one the points of this

It took me 10 minutes to do the whole computation by hand, so I wouldn't say it's a LOT of work. At the same time I believe this is also one the points of this experiment, to show how much work goes into computing a single pixel value for a very simple 3D scene which makes us appreciate more that our GPUs can do this work billions of times per second.