andrew wrote:When are these coordinate changes happening?
As soon as I opened a copy of a Q2 file withQ3.
andrew wrote:...I can imagine that the inaccuracy was already present in the QCAD 2 file
Actually, most of my values were typed as integer, some times at most with 2 decimals. If I change in Q3 a value like "281,999967" into a "281" and save the file, close Q3 and reopen the file, the integer value is there as "281" and not some "281,000000" and not scaled or adjusted to some internal number. What Q3 can do when processing its values, why is it impossible when opening a Q2 file ?
andrew wrote:- Small errors introduced when scaling entities up and down or rotating them...
I totally agree, also when extending a line until it crosses some other lines. But not when it comes about values entered at the keyboard.
What matters here is that all other entities touching an entity for which I change a value, must also be changed. Otherwise, you will get problems for instance when hatching an area. I guess 2 adjacent lines must have the same coordinates for the junction point including up to the 6the decimal ... or the 12th ???
andrew wrote:- Computers cannot represent all values (not even finite decimals) internally due to the way how they store numbers
Sorry, this time, I have to completely disagree with that position. As a professsional programmer for 40 years (and more to come), I had never a problem storing and retrieving integer values or fixed decimals ones. Merely a matter of selecting the right data type.
For instance an Ariane missile was lost because some internal routines were using 64-bits arithmetic and values where others were using 128-bits precision.
Simply, would you accept to receive a payement of an amount of 23,99 swiss Francs (QCAD 3 update) instead of 24,00 SWF ? Or a salary of approximately 4.999,98 € instead of 5.000,00 € ?