On 09/15/2017 10:00 AM, brynn wrote:
What is a "user unit" and what do you mean by "outside coordinate system"? Please don't explain anything below that unless you can't explain "user unit" and "outside coordinate system" otherwise. Hopefully once I understand those 2 things, the rest will make sense. But I need to go one step at a time.
The "outside coordinate system" is just the length of things upon displaying the file, assuming one respects the given "Size" of the document.
"Inside" the file, everything is measured with the "inside" coordinate system. This system's unit is the abstract "user unit": your document may have a rectangle measuring 2 user unit wide and 5 user units tall, and you can tell (in the viewBox) that your complete document is the area between the point of coord (0,0) and the point of coord (20,50), in user units.
They're abstract units, like when you do basic geometry in mathematics, without units; only meaning here that 2 user units wide is 10% of the document's width and 5user unit tall is 10% of the document's height. Only the additional data of the "Size" can tell you what the total height is in the "outside world", hence what 10% of it (== my 5uu of height) are worth.
Now, the units *inside* the file (like the "cm" in my post-scriptum) are only shortcuts for given, fixed, multiples of the user unit (by definition, "px" is the name of that user unit and "in" is the name given to 96 user units), but if you do not set "1 user unit is one outside-world-pixel", they're not worth what they seem.