I keep reading everywhere about "subdivision surfaces", which are
currently the "bing thing" in modelling software.  However, from the
explanations I gathered, they seems not much different from bezier
patches.  Can someone clarify this ?

Fabien.

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I've done a tiny bit of reading into them and from what I gather subdivision
is a function (to be applied on) of polygons.  In the software that supports
it a shape is made (and at the last minute) a subdivision is applied, where
everything is smoothed.  Depending on the settings a cube for example would
look like a sphere.  Its ideal for faces etc as you can create a low poly
mesh and subdivide at the end (which hugely increases the number of
polygons).

...Its not suitable directly for POV-Ray though someone could write a
macro/prog that could subdivide a mesh...

Peter Cracknell (.com)

"Fabien Mosen" <fab### [at] skynetbe> wrote in message
news:3AA0D441.BE1898C4@skynet.be...
> I keep reading everywhere about "subdivision surfaces", which are
> currently the "bing thing" in modelling software.  However, from the
> explanations I gathered, they seems not much different from bezier
> patches.  Can someone clarify this ?
>
> Fabien.

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Peter Cracknell wrote:

> ...Its not suitable directly for POV-Ray though someone could write a
> macro that could subdivide a mesh...

Someone already has :)

http://users4.50megs.com/enphilistor/sss.htm

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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Ken wrote:
> 
> Peter Cracknell wrote:
> 
> > ...Its not suitable directly for POV-Ray though someone could write
> > a macro that could subdivide a mesh...
> 
> Someone already has :)
> 
> http://users4.50megs.com/enphilistor/sss.htm

Unfortunately, it does not handle sharp edges or border edges (although
there is a way to work around that), and it is not terribly fast.

My modeler, which is currently in an ultra-slow rewrite, will be
supporting them.  However, that is waiting until I've got the
articulation
the way I want it (which will include a way to export a model as an .INC
file so that POV script code can animate it).

Once that work, the subdivision surface support will be added, then
UV-mapping.

Regards,
John

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In article <3aa2c539@news.povray.org>, "Peter Cracknell" 
<pc### [at] lineonenet> wrote:

> ...Its not suitable directly for POV-Ray

What do you mean? Subdivision could be very useful for POV-Ray...and I 
don't see anything about it that isn't "suitable". You can't even use 
the "POV is a renderer, not a modeller" argument with it, since 
subdivision isn't a modeller specific feature.


> though someone could write a macro/prog that could subdivide a 
> mesh...

As Ken mentioned, someone already has. ;-)

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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> > ...Its not suitable directly for POV-Ray
>
> What do you mean? Subdivision could be very useful for POV-Ray...and I
> don't see anything about it that isn't "suitable". You can't even use
> the "POV is a renderer, not a modeller" argument with it, since
> subdivision isn't a modeller specific feature.
>
>
> > though someone could write a macro/prog that could subdivide a
> > mesh...
>
> As Ken mentioned, someone already has. ;-)
>

Fair point, but when I picture subdivision in action I picture a modeller
actually in control and view of a mesh which then gets 'subdivided', POV-Ray
could subdivide therefore, but in general the subdivision will be of
imported mesh's won't it anyway?  So yes it could be used, just not as
ideally as people would like.

Peter Cracknell (.com)

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In article <3aa616a9@news.povray.org>, "Peter Cracknell" 
<pc### [at] lineonenet> wrote:

> Fair point, but when I picture subdivision in action I picture a modeller
> actually in control and view of a mesh which then gets 'subdivided', 
> POV-Ray could subdivide therefore, but in general the subdivision 
> will be of imported mesh's won't it anyway?  So yes it could be used, 
> just not as ideally as people would like.

I'm not sure I understand...subdivision would be used on meshes, height 
fields, and other mesh-based objects, and a lot of meshes are generated 
within scene files...and I don't see why it wouldn't be useful for 
imported meshes. You could get away with much smaller files, and get 
much lower RAM usage. (At the cost of some render time, though it could 
also be more efficient, by only subdividing triangles when necessary. 
And if you really want speed, you could subdivide the entire mesh before 
rendering.)
In fact, to get the best out of subdivision surfaces, you *have* to have 
it built into the renderer...there's no way around it.
Sure, you could also use a modeller, but then you are restricted to 
externally generated meshes, huge files, and high RAM requirements.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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"Chris Huff" <chr### [at] maccom> wrote in message
news:chrishuff-178997.11163210032001@news.povray.org...
> In article <3aa616a9@news.povray.org>, "Peter Cracknell"
> <pc### [at] lineonenet> wrote:
>
> > Fair point, but when I picture subdivision in action I picture a
modeller
> > actually in control and view of a mesh which then gets 'subdivided',
> > POV-Ray could subdivide therefore, but in general the subdivision
> > will be of imported mesh's won't it anyway?  So yes it could be used,
> > just not as ideally as people would like.
>
> I'm not sure I understand...subdivision would be used on meshes, height
> fields, and other mesh-based objects, and a lot of meshes are generated
> within scene files...and I don't see why it wouldn't be useful for
> imported meshes. You could get away with much smaller files, and get
> much lower RAM usage. (At the cost of some render time, though it could
> also be more efficient, by only subdividing triangles when necessary.
> And if you really want speed, you could subdivide the entire mesh before
> rendering.)
> In fact, to get the best out of subdivision surfaces, you *have* to have
> it built into the renderer...there's no way around it.
> Sure, you could also use a modeller, but then you are restricted to
> externally generated meshes, huge files, and high RAM requirements.

Obviously subdivision on imported meshes would be useful, but from what I've
read (and therefore reckon) is that the process of creating a mesh with
subdivision is a cycle of mesh editing, subdivision preview, mesh editing
repeat etc.  To do this with POV-Ray you would have to export subdivide
check, go back to your modeller edit and repeat.

To be fair I think my modeller bias is coming through so I'll probably leave
it there.  All in all subdivision is an extremely powerful tool that can
according to previews put many hours of work on organic objects to shame
very quickly.

Peter Cracknell (.com)

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