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

[Leonard Daly]

Justin,

X3D has no 'physical' nor 'length' tag/node. I do not know about Netfabb.

The UNIT statement was introduced in X3D V3.3 and may not be in 
Netfabb's allowed tag set.

You could wrap all geometry in a Transform AND use the metadata field to 
include text about why the scaling is done. As this would not be a 
comment, it would be less likely to be dropped during dissemination. I 
would also use a META statement in the header to highlight to the reader 
that it is scaled from mm to M in the Transform with the DEF name 
ConvertLengthUnitsFromMillimeters (for example).

Leonard Daly




> 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)?
>
> cid:image001.png at 01CE68DD.51995EF0
>
> cid:image002.jpg at 01D29DA3.311203E0
>
> 	
>
> *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/>
>
> 	
>
> cid:image001.png at 01CE68DD.51995EF0
>
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-- 
*Leonard Daly*
3D Systems & Cloud Consultant
LA ACM SIGGRAPH Past Chair
President, Daly Realism - /Creating the Future/
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