Hello,

I'm working on visualizing some simulation data with POVRay. Since what 
I'm dealing with is a set of 3D finite-element meshes, it looks like the 
best method is to convert the surface of my mesh into a POVRay mesh of 
smooth triangles and go from there. What I've done is split the 
quadrilaterals I have into triangles and compute normal vectors with a 
bunch of cross products. This works OK, but it has some problems, such 
as the shadow line artifact. Also, I don't see any easy way to 
distribute a range of colors on the surface of the mesh to represent a 
variable (ie, pressure or velocity magnitude).

What (I think) I'd like to do is split the elements of my mesh into many 
more elements and smooth it out. I've found a few sets of macros and 
things for doing this, like the "New Surface Subdivision Suite" (
http://www.geocities.com/evilsnack/nsss.htm ) and "POV-Ray with 
Subdivision". They all seem to be unmaintained, though, or at least very 
out of date. Does anyone here have a preferred way of smoothing / 
subdividing meshes? Also, is there any experience out there in general 
with using POVRay with finite element analysis data? I know that's not 
at all what it's designed for, but I think it could be very useful for 
generating images for presentations/posters/etc. Thanks,

Jesse

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Jesse Connell wrote:

> Does anyone here have a preferred way of smoothing / 
> subdividing meshes?

Yes, I use the aforementioned "POV-Ray with Subdivision" It's good for 
many things, though it suffers from strange artifacts sometimes. I 
mention it because I hope more people will start using it, and then 
maybe it will be supported in the new version of POV.

~Sam

Post a reply to this message

Jesse Connell wrote:
> Hello,
> 
> I'm working on visualizing some simulation data with POVRay. Since what 
> I'm dealing with is a set of 3D finite-element meshes, it looks like the 
> best method is to convert the surface of my mesh into a POVRay mesh of 
> smooth triangles and go from there. What I've done is split the 
> quadrilaterals I have into triangles and compute normal vectors with a 
> bunch of cross products. This works OK, but it has some problems, such 
> as the shadow line artifact. Also, I don't see any easy way to 
> distribute a range of colors on the surface of the mesh to represent a 
> variable (ie, pressure or velocity magnitude).
> 
> What (I think) I'd like to do is split the elements of my mesh into many 
> more elements and smooth it out. I've found a few sets of macros and 
> things for doing this, like the "New Surface Subdivision Suite" (
> http://www.geocities.com/evilsnack/nsss.htm ) and "POV-Ray with 
> Subdivision". They all seem to be unmaintained, though, or at least very 
> out of date. Does anyone here have a preferred way of smoothing / 
> subdividing meshes? Also, is there any experience out there in general 
> with using POVRay with finite element analysis data? I know that's not 
> at all what it's designed for, but I think it could be very useful for 
> generating images for presentations/posters/etc. Thanks,
> 
> Jesse


PoseRay can subdivide meshes and export them to POV code. Load a mesh 
and in the groups tab select subdivision and then press update. There 
are several options you can play with for different results.

http://mysite.verizon.net/sfg0000/

good luck,

FlyerX

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MeshLab can subdivide, cull, re-mesh etc.
(but it's not a modeler)
http://meshlab.sourceforge.net/

Wings3d can subdivide stuff.
http://www.wings3d.com/

And of course you'll need PoseRay
to import stuff.
http://mysite.verizon.net/sfg0000/

Post a reply to this message

Thanks for all the advice! I'm leaning towards POV-Ray with Subdivision 
right now, mostly because the format conversions look like they'll be a 
bit of a pain otherwise. (Too bad there's no source available for 
PoseRay; it looks useful but I'd rather not fiddle with Wine at the moment.)

A few last questions for whoever might know: Is it likely that POV-Sub 
will make it into the official packages in the future? Also, what's with 
the three years without an update to the website/code? (That was what 
worried me in the first place.) And finally, if I have color set at each 
triangle in a mesh, would POV-Sub do something to interpolate them when 
subdividing? (Don't want to get my hopes up, but that would be pretty 
great.) Thanks again,

Jesse

Post a reply to this message

Jesse Connell wrote:
> (Too bad there's no source available for 
> PoseRay; it looks useful but I'd rather not fiddle with Wine at the 
> moment.)

I'd like to second that. :-)

-- 
William Tracy
afi### [at] gmailcom wtr### [at] calpolyedu

You know you've been raytracing too long when you know how far away a 
scene's light source is just by looking at the shadows.
Taps a.k.a. Tapio Vocadlo

Post a reply to this message

Jesse Connell <jes### [at] buedu> wrote:
> Also, I don't see any easy way to
> distribute a range of colors on the surface of the mesh to represent a
> variable (ie, pressure or velocity magnitude).

I've never tried it, but if you use a mesh2 object you can texture triangles
or even vertices individually. It looks like you need to put the textures
into a list and reference them by index but it can be done.

http://www.povray.org/documentation/view/3.6.1/293/

Bill

Post a reply to this message

Bill Pragnell <bil### [at] hotmailcom> wrote:
> I've never tried it, but if you use a mesh2 object you can texture triangles
> or even vertices individually.

  Actually you can do that with a mesh too, but it becomes more verbose.

-- 
                                                          - Warp

Post a reply to this message

Ah, I hadn't notice the individual vertex possibility. That's definitely 
something I can use. Thanks!

Jesse

Warp wrote:
> Bill Pragnell <bil### [at] hotmailcom> wrote:
>> I've never tried it, but if you use a mesh2 object you can texture triangles
>> or even vertices individually.
> 
>   Actually you can do that with a mesh too, but it becomes more verbose.
>

Post a reply to this message

Jesse Connell wrote:
...
> What (I think) I'd like to do is split the elements of my mesh into many
> more elements and smooth it out. I've found a few sets of macros and
> things for doing this, like the "New Surface Subdivision Suite" (
> http://www.geocities.com/evilsnack/nsss.htm ) and "POV-Ray with
> Subdivision". They all seem to be unmaintained, though, or at least very
> out of date.
...

Jesse,
Last time I tried the NSSS macros they worked very well, so I don't
think that the suite needs much maintenance at the moment.

Here's some images I rendered with NSSS (and some macros of my own):
http://home.online.no/~t-o-k/POV-Ray/Mesh-Moebius_Band.jpg
http://news.povray.org/povray.binaries.images/thread/%3C41450e47%40news.povray.org%3E/
http://news.povray.org/povray.binaries.images/thread/%3C4131f02f%40news.povray.org%3E/

-- 
Tor Olav
http://subcube.com

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Tor Olav Kristensen wrote:
> Jesse Connell wrote:
> ...
>> What (I think) I'd like to do is split the elements of my mesh into many
>> more elements and smooth it out. I've found a few sets of macros and
>> things for doing this, like the "New Surface Subdivision Suite" (
>> http://www.geocities.com/evilsnack/nsss.htm ) and "POV-Ray with
>> Subdivision". They all seem to be unmaintained, though, or at least very
>> out of date.
> ...
> 
> Jesse,
> Last time I tried the NSSS macros they worked very well, so I don't
> think that the suite needs much maintenance at the moment.
> 
> Here's some images I rendered with NSSS (and some macros of my own):
> http://home.online.no/~t-o-k/POV-Ray/Mesh-Moebius_Band.jpg
>
http://news.povray.org/povray.binaries.images/thread/%3C41450e47%40news.povray.org%3E/
>
http://news.povray.org/povray.binaries.images/thread/%3C4131f02f%40news.povray.org%3E/
> 

OK, thanks. I thought that might be the case. Glad to hear from someone 
who's used it. Like you say, it looks like it works pretty well!

Jesse

Post a reply to this message

Tor Olav Kristensen wrote:
> Jesse Connell wrote:
> ...
> 
>>What (I think) I'd like to do is split the elements of my mesh into many
>>more elements and smooth it out. I've found a few sets of macros and
>>things for doing this, like the "New Surface Subdivision Suite" (
>>http://www.geocities.com/evilsnack/nsss.htm ) and "POV-Ray with
>>Subdivision". They all seem to be unmaintained, though, or at least very
>>out of date.
> 
> Last time I tried the NSSS macros they worked very well, so I don't
> think that the suite needs much maintenance at the moment.

Maintenance happens when the maintainer is told there is a bug.  That 
hasn't happened in a while (almost three years), so there's been no need 
for updates.

At the moment I am upgrading my modeler to use polygons with more than 
four sides, and I'm rewriting my macro suite to go with it.  There will 
be an appropriate announcement when it's ready to be seen in public.

Regards,
John

Post a reply to this message

John VanSickle wrote:
> Tor Olav Kristensen wrote:
>> Jesse Connell wrote:
>> ...
>>
>>> What (I think) I'd like to do is split the elements of my mesh into many
>>> more elements and smooth it out. I've found a few sets of macros and
>>> things for doing this, like the "New Surface Subdivision Suite" (
>>> http://www.geocities.com/evilsnack/nsss.htm ) and "POV-Ray with
>>> Subdivision". They all seem to be unmaintained, though, or at least very
>>> out of date.
>>
>> Last time I tried the NSSS macros they worked very well, so I don't
>> think that the suite needs much maintenance at the moment.
> 
> Maintenance happens when the maintainer is told there is a bug.  That 
> hasn't happened in a while (almost three years), so there's been no need 
> for updates.
> 
> At the moment I am upgrading my modeler to use polygons with more than 
> four sides, and I'm rewriting my macro suite to go with it.  There will 
> be an appropriate announcement when it's ready to be seen in public.
> 
> Regards,
> John

I've ended up putting my meshes through the NSSS macros, and they're 
working great for me. Thanks for quelling my fears about maintenance; it 
looks like I spoke too soon in my first post.

Jesse

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