[x3d-public] [cad] STL File Format for 3D Printing - Simply Explained | All3DP

[Leonard Daly]

Adding support for STL makes a lot of sense, though I did not find any 
references to a "standard".

STL files contain just geometry information, while glTF and SRC files 
(can) contain material or texture in additional to geometry. Also glTF 
V1 and V2 files can contain Transform and multi-mesh geometry. STL files 
are much more similar to TriangleSet node (without color). There are 
extensions for adding color to an STL; however, non of the formats are 
standardized and there are conflicts between them. See 
https://en.wikipedia.org/wiki/STL_(file_format)#Color_in_binary_STL for 
more information.  It might make more sense to add a 'src' attribute to 
the TriangleSet node that indicates an external source for the 
definitions of the triangles and normals.

One issue that would need to be address (at least in the text) is that 
STL vertices are always positive. That is not in contradiction with X3D, 
but is not necessarily aligned with the common "mind-set" of the 
objected centered at the origin.

Along the same lines, it would probably make sense to add a 'src' 
attribute to the Transform and Group nodes to indicate that the source 
is external. This extension would support glTF files. Additional work on 
Physically Based Rendering and animation would also be necessary to 
support glTF V2 files.

Leonard Daly



On 8/13/2017 6:35 PM, Don Brutzman wrote:
> Good article of general interest:
>
>     STL File Format for 3D Printing - Simply Explained | All3DP
>     June 13, 2017 bub Dibya Chakravorty
>     https://all3dp.com/what-is-stl-file-format-extension-3d-printing
>
> Interesting thought question:
>
> -if we follow Fraunhofer's SRC pattern and have both ExternalShape and 
> ExternalGeometry nodes,
> -  and now replace SRC with glTF 2, then
> - might we similarly allow loading of STL models in ExternalShape and 
> ExternalGeometry nodes?
>
> all the best, Don


-- 
*Leonard Daly*
3D Systems & Cloud Consultant
LA ACM SIGGRAPH Chair
President, Daly Realism - /Creating the Future/
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