3ds max to Chitubox scaling issue

12 Months+ 209

models from 3ds Max are coming into chitubox much smaller.

in 3dsMax a sphere is 100mm. the same sphere imported into Chitubox is 7.87mm

any way to make this match without scaling in chitubox?

i'm using chitubox vers. 1.9.1

New Post (3)
  • Cliff Knight 12 Months+
    Quote 2Floor

    .STL STL files do not save the physical dimension of a unit, all they know is that a "length" of 1 unit is one "something" or other.  

    This post in the Autodesk forum says the default unit in 3ds is 1 inch. This is 25.4 times larger than what Chitubox assumes is a "unit" (1 mm), leading me to believe your "100 mm" 3ds sphere is 100 "units" in radius, or 200 "units" diameter--with 3ds believing each unit is 25.4 X larger than what CB believes a unit to be

    200 "units" / 25.4 = 7.874

  • 12 Months+
    Quote 3Floor
    Cliff, thanks for the reply!
    so that's kind of crazy. In theory then Chitubox scales up models 25.4% because STL doesn't keep consistent scale?
    this seems like a fundamental issue that developers would have fixed long ago
    Thanks Cliff!
  • Cliff Knight 12 Months+
    Quote 4Floor

    It is not a Chitubox issue, other than that CB assumes the unit of measure to be millimeters (as do most 3D CAD applications). The .stl file format (invented in 1987 by the Albert Consulting Group for 3D Systems) does not specify any unit of measure, it just quantifies how many units there are--it is up to systems sharing .stl files to agree upon a unit to use--this is a good thing as it makes the files universal.

    .stl does keep "scale"--that is why the sphere remained a sphere--however it does not specify any specific unit of measure, which is why it was reconstructed as a smaller sphere.

    This Wikipedia article explains this further.

    Your experience is a configuration issue with your 3ds application is--make sure it is set to the metric system with 1 unit = 1 mm.

    CB is actually "scalling" down as it believes each .stl "unit' is 25.4 X smaller (BC believes  "unit' = 1 mm) than your 3ds application which believes 1 "unit" = 1 inch.

    It might be "handy" if the unit of measure were configurable in Chitubox, but that's about it, applications used to create .stl content always are--just make sure they are set to 1 "unit' = 1 mm if CB is the intended destination.

    FWIW; FreeCAD lets you change the units of measure for its own display and user interaction purposes, but it aways "thinks" and creates .stl files assuming a "unit" is 1 mm...