No one used sequential trig calls; it was still all matrix multiplications, and such. If you're trying to explain the effects without jumping into matrices though, calculating the trig like that is the way to do it.
The for loops are always present, but they're handled in the driver or the hardware itself. If you assume that all you've got for drawing graphics is a setPixel function, then they end up exposed directly in your code.
The for loops are always present, but they're handled in the driver or the hardware itself. If you assume that all you've got for drawing graphics is a setPixel function, then they end up exposed directly in your code.