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out of date.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

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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

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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

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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

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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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