The PlayStation 1 performed all calculations in fixed point. On the face of it, this is straightforward enough; it couldn't afford floating-point hardware, which was introduced only later, with the PS2, thereby allowing the PS2 to perform 3D calculations with better accuracy.
But there are a few reasons I'm not quite satisfied with this account.
For one thing, fixed point is not necessarily cheaper to calculate than floating point, e.g. 32-bit fixed-point multiply actually costs more than 32-bit floating point multiply: https://electronics.stackexchange.com/questions/368862/transistor-count-of-floating-point-multiplier
For another thing, it's also not necessarily inferior, e.g. a commenter on https://www.quora.com/Why-didnt-the-original-Playstation-support-floating-point
You don't really need floating-point numbers for most things. The only time you "need" them is for astronomical or molecular calculations where the values are so large and/or so small that precision is not important.
Fixed-point values a greater precision (using the same number of bits because there are no bits wasted on the exponent) and 32-bits offer enough dynamic range for any video-game simulation to appear fluid. It's actually more work to use floating-point numbers because they introduce more instabilities due to their quirky rounding behaviors and conversion between internal formats and IEEE-754 format and you have to ensure all the code is written taking this into account. (e.g. You can't just normalize 32-bit floating-point vectors once ... you have to normalize them twice for them to end up actually normal.)
Even today, if you want speed and stability you still use fixed-point values. Floating-point computations are toys for research to make it easier. When it's time to engineer a real product, fixed-point dominates.
Now, I'm not endorsing that view as the whole truth. For example, fixed point requires all code plus input data a given program to agree on the required dynamic range, so at the least, floating point would have become mandatory for games by the PS3 era when, as Sweeney observed, it became commonplace for a game to incorporate 10-20 middleware libraries. Still, it does indicate that the story is not as simple as it looked at first glance.
But one thing fixed point does give you is the opportunity to cheat, to take shortcuts, to use less than full 16.16 precision. Maybe that was the tradeoff made on the PS1.
What precision did PlayStation 1 games typically use for 3D calculations?