Fix vertex offset

[khdlr]

Fixes #30

[FlorianK13]

@khdlr Have you tested then new 0.01 tolerance in the webgl code with actual data used on the website?

[khdlr]

@khdlr Have you tested then new 0.01 tolerance in the webgl code with actual data used on the website?

Yes, I played around a bit with different values between 0.0 and 0.05, it seems that 0.05 is too high. Things seem to work even with 0.0, but I'm scared of floating point errors here...