Exact values become imprecise

Development Programming & Scripting
1

There is a bug with the precision of entered values, this is known, but i could’nt find it in the bugs section

I guess it is best explained in this :

: Currently there is an issue with some of the variables in UE4 not being set to an exact number. For instance, certain values you may enter, lets say 50, may actually be set to something like 49.9998. This isn’t happening in the background though, it will change the 50 you entered to 49.9998. Our developers are looking into this and we hope to have a solution soon.

Is this still being looked into ? that is from june '14 …

2

Hi FrederickD,

This is typically a float point error and unfortunately is not something that can be resolved unfortunately. You can find more information on Float Points here:

3

I understand it has something to do with that… but other applications such as blender don’t have this problem, at least not that much…

In unreal even when you enter an integer - i mean a rounded float, it get’s messed up …

4

Indeed, especially when it f* up your level light and collision when walls are not connected 90°…having some random 89.9438° numbers instead. Cinema 4D had this floating point problem several years ago. They fixed this and other issues by rebuilding the core from scratch, using double precision like…UE4?

Maybe…it helps to code a feature that UE4 is actually rounding up the numbers on the input fields to “fake” solve this issue.

5

The real solution to this is to internally store all “float” data as an integer with an exponent. So “12.5” is actually “125 x 10^-1”.

This gets you exact decimals every time.

6

exactly, came across something like that too, even as an unreal plugin, mainly for use with ingame currency:

Not that it would have to be 128bit for transforms, but allaz, at least it is possible. Not sure how much slower this would be though, and would need to be transformed into floats for the gpu anyway.