Hi Pilou, also in MoI (and other solid modelers) there are also additional issues beyond just the basic accuracy of fundamental arithmetic - MoI and other solid modeling systems often need to calculate results to an approximated level of accuracy.

In MoI this is the fitting tolerance which is 0.001 units in size.

So when you do things like a boolean operation, when MoI calculates the intersection between 2 surfaces it will do some calculations where it continues to increase the accuracy of the result until it is at least 0.001 units from the "true" result. There are many operations for which the completely accurate result is just too heavy to calculate.

So operations that involve this kind of fitting process will not tend to work very well in a solid modeling program if you have objects that are greatly larger or greatly smaller than the fitting tolerance.

That's just another area that tends to make things like modeling a solar system at a scale of 1 to 1 not work very well with a solid modeling program.

Generally with MoI you should try to keep your numbers in a range of something like 0.01 to 3000.0 to get good results.

- Michael