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Hello,
I am trying to render a glass of wine, but I have some mesh problems.
The picture vino.jpg shows the problem
the different objects are exported from Pro Engineer in obj files,
between 5000 and 6000 triangles.
The result is very strange!
I tried different settings, I also tried to let 0.1 mm space between
wine and glass, but without sucess.
Finally, I increased the precision in Pro/Engineer and managed to export
these objects with about 5000
triangles for the wine and more than 200000 triangles for the glass.
I render the scene with povvray 3.5 to see the difference (vino3.jpg)
The problem is still here, but what is interesting is that:
-The glass alone gives good results
-The wine alone gives good results
-Putting the wine in the glass gives this poor result!
the problem is the same when rendering with Virtualight for example
The questions are:
1) Is it possible to render properly a plain glass with meshes or must I
realise this with SDL
to have a correct result?
2) Is there some options in Povray that could supress or reduce this
problem?
(I tried to increase max trace level to 30 without success)
3) Is this an optical problem?
Any comments, suggestions are welcome.
best regards
philippe Hay
Post a reply to this message
Attachments:
Download 'vino.jpg' (10 KB)
Download 'vino3.jpg' (78 KB)
Preview of image 'vino.jpg'
Preview of image 'vino3.jpg'
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Looks like the same kind of granularity errors that result from field
rendering in pov. Does this help at all?
A.D.B.
philippe Hay wrote:
> Hello,
>
> I am trying to render a glass of wine, but I have some mesh problems.
>
> The picture vino.jpg shows the problem
> the different objects are exported from Pro Engineer in obj files,
> between 5000 and 6000 triangles.
>
> The result is very strange!
>
> I tried different settings, I also tried to let 0.1 mm space between
> wine and glass, but without sucess.
>
> Finally, I increased the precision in Pro/Engineer and managed to export
> these objects with about 5000
> triangles for the wine and more than 200000 triangles for the glass.
> I render the scene with povvray 3.5 to see the difference (vino3.jpg)
>
> The problem is still here, but what is interesting is that:
>
> -The glass alone gives good results
> -The wine alone gives good results
> -Putting the wine in the glass gives this poor result!
>
> the problem is the same when rendering with Virtualight for example
>
> The questions are:
>
> 1) Is it possible to render properly a plain glass with meshes or must I
> realise this with SDL
> to have a correct result?
>
> 2) Is there some options in Povray that could supress or reduce this
> problem?
> (I tried to increase max trace level to 30 without success)
>
> 3) Is this an optical problem?
>
> Any comments, suggestions are welcome.
>
> best regards
>
> philippe Hay
>
> ------------------------------------------------------------------------
> [Image] [Image]
Post a reply to this message
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is this not a problem where two objects share the same surface, and pov
doesn't know which to test first? (or something like that)
Post a reply to this message
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This looks for all the world like some kind of coincident surfaces problem -
but if you say you put 1mm of space between the two surfaces, then I suppose
it can't be... (You're sure you added 1mm of SPACE rather than 1mm of
OVERLAP by mistake? <grin> Actually, either way should have solved it
anyway...) You might try adding a little more space... not much else I can
think of to suggest really... I would have expected 1mm to do it... Unless
the problem is something totally different of course!
Sorry.
Andrew.
Post a reply to this message
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If you want it to look realistic (speaking of refractions
here), you want the objects to overlap, POV handles
the refraction-changes properly then.
As about your other problem, I guess the exported meshes
don't fit as you might want them to, otherwise I don't think
POV would come up with this nice and regular spherical
pattern.
--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmx de
> This looks for all the world like some kind of coincident surfaces problem -
> but if you say you put 1mm of space between the two surfaces, then I suppose
> it can't be... (You're sure you added 1mm of SPACE rather than 1mm of
> OVERLAP by mistake? <grin> Actually, either way should have solved it
> anyway...) You might try adding a little more space... not much else I can
> think of to suggest really... I would have expected 1mm to do it... Unless
> the problem is something totally different of course!
>
> Sorry.
> Andrew.
>
>
Post a reply to this message
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philippe Hay wrote:
> Hello,
>
> I am trying to render a glass of wine, but I have some mesh problems.
make the wine object slightly smaller - something like .0001
--
Rick
Kitty5 NewMedia http://Kitty5.co.uk
POV-Ray News & Resources http://Povray.co.uk
TEL : +44 (01270) 501101 - FAX : +44 (01270) 251105 - ICQ : 15776037
PGP Public Key
http://pgpkeys.mit.edu:11371/pks/lookup?op=get&search=0x231E1CEA
Post a reply to this message
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philippe Hay wrote:
> Hello,
>
> I am trying to render a glass of wine, but I have some mesh problems.
>
>
> The picture vino.jpg shows the problem
> the different objects are exported from Pro Engineer in obj files,
> between 5000 and 6000 triangles.
>
> The result is very strange!
>
> I tried different settings, I also tried to let 0.1 mm space between
> wine and glass, but without sucess.
>
Even though you use smoothtriangles in the image the rays are computed
using the underlying triangles. This means that if the glass and wine
have same size of triangles, you are sure to have some overlap, if
they are rotationally not aligned. Indeed using some space between
the two object should get rid of it and you say it did not. (Athough
not knowing the scale of the triangles i do not know if .1 mm is enough)
Anyway, to test if it has anything to do with this kind of overlap, try
rotating the wine a bit and not the glass.
Andrel
Post a reply to this message
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Thanks a lot for all of you,
The problem is solved!
In fact, it was really a problem with coincidence surfaces.
my first tests were done with only about 5000 triangles, and with both
version:
- surface of wine is in contact with glass
- surface of wine is offset by amout 0.1 mm
The second test vino3.jpg with more triangles had still a surface of
wine in contact with the glass.
So I have now add a gap again between glass and wine and it gives very
good results.
I also play with some parameters in my CAD programs, so I only need
about 8000 triangles.
I only have a PII, and it takes always a lot of time to realise such
rendering, it is a nightmare, specially in the test phase.
I hope I will send you a nice picture in some weeks, in fact I wanted to
render a broken glass, and to see some interesting caustics effects.
Post a reply to this message
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Hm, mentioned this several times throughout the last
days to several people:
For refraction working properly when entering from one
medium to another (like from air into glass, from glass
into water etc) you objects to overlap, not leave a gap.
--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde
> Thanks a lot for all of you,
>
> The problem is solved!
>
> In fact, it was really a problem with coincidence surfaces.
> my first tests were done with only about 5000 triangles, and with both
> version:
>
> - surface of wine is in contact with glass
> - surface of wine is offset by amout 0.1 mm
>
> The second test vino3.jpg with more triangles had still a surface of
> wine in contact with the glass.
> So I have now add a gap again between glass and wine and it gives very
> good results.
> I also play with some parameters in my CAD programs, so I only need
> about 8000 triangles.
>
> I only have a PII, and it takes always a lot of time to realise such
> rendering, it is a nightmare, specially in the test phase.
> I hope I will send you a nice picture in some weeks, in fact I wanted to
> render a broken glass, and to see some interesting caustics effects.
>
>
>
>
>
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Tim Nikias wrote:
> Hm, mentioned this several times throughout the last
> days to several people:
> For refraction working properly when entering from one
> medium to another (like from air into glass, from glass
> into water etc) you objects to overlap, not leave a gap.
>
Hallo Tim,
Yes I read you in this trhead, Thanks for this trick, I will test the
overlapping this evening, I just had so few times..
Philippe Hay
Post a reply to this message
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