[osg-users] TriStripVisitor issue

Emmanuel Roche roche.emmanuel at gmail.com
Mon Nov 23 06:10:17 PST 2009


Hi Robert,

Actually, I've noticed that the problem doesn't come from the underlying
tristripper library:

instead, it seems that the indice array generated from my vertices is
incorrect: I suspect that the comparison function to find if too vertices
are the same or not is too precise in my case. Do you have a clear idea
where this is done ? (otherwise, I will just read more code and find it...)

cheers,

Manu.



2009/11/23 Emmanuel Roche <roche.emmanuel at gmail.com>

> Actually, I also noticed that OSG v2.8.1 uses version 1.0 of the
> tristripper library.
>
> As I'm quite in an hurry, I think I will re-implement my own
> tristripvisitor with the latest version of tristripper and check if this
> makes a difference. Will let you know what's the result of this test.
>
> But I believe this could really be a generic issue (it happens with all the
> models I tested) and thus would mean many people are currently using "not so
> well tri-stripped" geometries if they use this optimiser feature !  (it is
> the case for instance in the OSGExp export plugin for 3DS max as I've
> noticed this issue there for the first time).
>
> regards,
> Manu.
>
>
>
> 2009/11/23 Robert Osfield <robert.osfield at gmail.com>
>
> Hi Manu,
>>
>> If the tristripper doesn't connect the triangles together well then it
>> can result on few tristrips and lots of unconnected traingles that it
>> has to put into a single list of triangles to avoid lots of separate
>> primitive calls.
>>
>> As to why your model is not being stripped well I can't say.  We've
>> used 3rd party code to do the tri-stripping so I'm not best placed to
>> answer the low level questions, but... the original author of the cdoe
>> Tanguy Fautre is now an OSG user and I believe still on the list so
>> perhaps he'll be able to chip in ;-)
>>
>> Robert.
>>
>> On Mon, Nov 23, 2009 at 11:08 AM, Emmanuel Roche
>> <roche.emmanuel at gmail.com> wrote:
>> > Hi everyone,
>> >
>> > I have a strange problem with the TryStripVisitor:
>> >
>> > When I use it on a model (with about 6000 triangles, described as
>> TRIANGLES
>> > [thus using 18000 vertices]) I get trip strip primitive sets indeed....
>> BUT
>> > actually I get a few TRIANGLE_STRIP primitive sets with 4 vertices in
>> each,
>> > and then a single big TRIANGLES primitive set with about 17950 vertices
>> !!!!
>> >
>> > So, most of the model is just not stripped at all ! any idea what I
>> could be
>> > doing wrong ???
>> >
>> > Moreother, I've noticed that the geometry is then transformed as an
>> indexed
>> > geometry... correct me if I'm wrong but indexed geometries are slower
>> that
>> > simple vertices ordered arrays. If there a way to switch this or am I on
>> my
>> > own on this ?
>> >
>> > Regards,
>> > Manu.
>> >
>> >
>> >
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>> >
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>> >
>> >
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