Re: [rp-ml] Colour STL files?

From: steve <>
Date: Sun Nov 05 2006 - 23:50:06 EET

Adrian Bowyer wrote:
> Quoting Todd Pederzani <>:
>> steve wrote:
>>> I strongly urge all software vendors
>>> to support (at a minimum) PLY and COLLADA and to try to wean
>>> their customers off of STL as fast as they can run away!
>> You and I may agree, as programmers, that the STL format has
>> shortcomings, but from a user's perspective it "works."
> No it doesn't. I've lost count of the number of people coming to me
> with STL files that simply won't build because they do not obey the
> Euler formula for a solid.

That's not a problem that a change in file format will solve though.

An unconnected object will be unconnected no matter what format you
save it in - so unless you somehow represent geometry as CSG, you'll
always have files that might potentially be disconnected.

PLY is much more compact than STL because each full vertex description
is saved only once. It also allows arbitary additional data (such as
colour - but perhaps others) to be stored at each vertex. There is only
one way to represent colour - not two incompatible ways as with STL so
I presume compatibility would be better. There is a standard library
provided for reading PLY files that allows convenient support for truly
vast triangle meshes.

COLLADA is an XML-based format, it's not especially compact but it has
huge support in non-RP communities - so lots of tools support it. There
are benefits to XML just because XML is very web-friendly. You can
import an XML file into a Java program with one line of code and
traverse it's hierarchy very easily. You can also represent multiple
objects in one COLLADA file - which you aren't supposed to do with STL
or PLY.

> That you can check it against the Euler-Poincaré formula - simple (and
> fundamental) as that.

I guess so.
Received on Tue Dec 05 22:39:16 2006

This archive was generated by hypermail 2.1.8 : Tue Jul 21 2009 - 10:27:52 EEST