Hi Chris,
I have slowly gone from AD to Vstyler for C3D and had to check the same SVG import ratio for C3D.
Seems the following is true in Vstyler:
1 point = 0.035 cm / 0.014 inch > c3d value 1.0
To test this I made a 300dpi doc size and exported in 300dpi in Vstyler in both 1x1 cm and 1x1 inches (two files) > SVG. Then I first tested cm by setting C3D SVG import to 0.035 and compared to a cube with height / width eq 1.0 in c3d. Same size. Then I can work in centimeters in Vstyler and directly know that for my 3D prints I can interpret the size system on C3D as in centimeters for all my spline imports / modelling.
I also tested this for you by changing the c3d svg import value to 0.014 inches. I imported the 1x1 inch square from Vstyler and it matches the same cube set to 1.0 height / width. In other words then you can interpret the c3d value as inches.
In Affinity Designer the same issue occurs for me when doc dpi is set to 300 vs 72 (See image). To understand this I opened the SVGs in Texteditor to compare to the output of Vstyler. Notice the image attached that the Matrix is different but the size the same in the AD SVG export.
You can read more about the AD situation here:
https://forum.affinity.serif.com/in...-svg-export-transform-matrix-rounding-errors/
So if you want to use 300 DPI in AD you can follow my older posts; or use pixels. I will go for Vstyler as it includes all the stuff that I miss in A.D. Still prefer the UI of A.D. but small price to pay.
Hope it helps.
Thanks Frank as always for your input
Moo.