[x3d-public] Alternate Units for X3D and 3D Printing

[Ryan, Justin]

Hello X3D Public List,

I was hoping someone could answer a question for me regarding units. I have been translating STL to X3D for medical 3D models. While the STLs are technically unitless, the de facto standard unit of medical 3D reconstruction is mm. A direct conversion means that the X3D are scaled up by a factor of 1000.

While I am working on creating a script to scale the coordinate points, I was also hoping on utilizing xml tags to also scale.

I attempted adding the following (separate and together); however, opening the files in netfabb had zero impact on its import scale.

Option 1 (right after opening scene tag):
<physical><length unit="MILLI" basis="1" numeral="DEC"/></physical>

Option 2 (right after opening head tag):
<unit category='length' conversionFactor='0.001' name='millimeters'/>

Any ideas as to why neither of these fixed my scale issue? Besides changing the actual coordinate points (dividing all by 1000), are there other unit tags that might be opened by netfabb? My concern with using a <transform scale...> is that the reason why there is a scale might be lost if the files were being disseminated.

Last follow-up question, what is the maximum precision of coordinate points within X3D (if I do go the divide by 1000 route)?

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Justin Ryan, PhD
Arizona State University Adjunct Faculty
Phoenix Children's Hospital Research Scientist



Phoenix Children's Hospital
Cardiac 3D Print Lab



p (602) 933-3902



Cardiac3DPrintLab.com<http://cardiac3dprintlab.com/>



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