Moho Forum

Posted: **Mon Sep 25, 2006 6:17 pm**

I have all the info... I just don't have the skills.

This is the code for a shape named "1" on a 4 point box with a stroke width of "5". The highlighted line is the stroke width in the file format.

The document height is 540px. That highlighted number times... approximately 540 equals practically... uh... 5. This is consistent with stroke widths and pixel heights of projects.

Neither number (the stroke or the pixel height) is the "exact" number... but is so close as to not make a spit of difference... but could be a problem trying to... change this by typing in a number or changing all the "5" widths to "7" or something like that. It is always... like... instead of 5... 4.99986...
Instead of "540" it would be something like... 539.99808001536.

Code: Select all

		shapes 1
			"1" false true true true
				4
					0 0
					0 1
					0 2
					0 3
				""
					false
					[
						keys 1
							0 0 0.1 0.5 1 1 1 1
					]

Code: Select all

					false 0.009259

Code: Select all

					false
					[
						keys 1
							0 0 0.1 0.5 1 0.129412 0.129412 1
					]
					""
					false
					6.283185
					0.25
					true
					-1
					-1
					-1
				""
				""

-vern

Posted: **Tue Sep 26, 2006 3:10 am**

Hello Vern,

ahh, the wonders of floating point inaccuracy.

Partly because infinite or even long decimal fractions cannot be represented in the very finite storage allocated to each floating point number on the computer, partly because humans work in base 10 and computers work in base 2 - for example, I believe it is impossible to exactly represent 0.1 in binary, just as it is impossible to accurately represent 1/3 in decimal format (0.33333333333333333333333333333333333333...etc).

You could use a look-up table tailored to your document height, but that seems rather clunky.

How about something like this (taken from the Lua users wiki):

Code: Select all

Lua 5.0.2  Copyright (C) 1994-2004 Tecgraf, PUC-Rio
> decimal_points = 6
> line_width = 5
> project_height = 240
> somenumber=tonumber(string.format("%."..decimal_points.."f", line_width/project_height))
>
> =somenumber
0.020833
>


> project_height = 540
> somenumber=tonumber(string.format("%."..decimal_points.."f", line_width/projec
t_height))
>
> =somenumber
0.009259

Regards, Myles.

Posted: **Tue Sep 26, 2006 6:41 am**

Sometimes I feel Moho's internal floating point is float (4 bytes long) and not double (8 bytes). That's why it is not so accurate. I am talking about the internal values (ie. the values of the keys in the animated channels) but Lua using double for the numbers.

Moho Forum

Global stroke width change?

Global stroke width change?