How to work with gigantic objects?

[Zoot]

There are not enough bits in single precision floating point numbers to represent all the positions in space that you need so the math goes wonky. See:

Cycles sun cast shadow position is WRONG!

Perhaps the biggest issue currently is that Nvidia in recent generations of their video cards have decided double-precision is a “pro” feature and consumer cards have no hardware acceleration for DP so things end up 24-32 times slower when you try to do DP calculations in CUDA compared to SP, so you would lose Cycles GPU compute on consumer Nvidia cards if Cycles switched to 64-bit double-precision floats. If AMD starts offering cheap DP performance then maybe Nvidia will have to change its way…