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From: Micha Riser
Subject: Re: I really really want n-sided bezier patches...
Date: 23 Aug 2002 12:45:54
Message: <3d6666c2@news.povray.org>
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Rune wrote:
>
>> The program works as expected.
>
> Now it does. :)
It does no more :(
>
>> To solve your problem one probably has to add support
>> for arbitrary edge points in uv-space for the triangle.
>
> The uneven distribution and the UV mapping are two completely different
> issues. The UV mapping never was a problem, and as I said earlier, I do
> indeed intent to add support for custom UV vectors for the UV mapping.
> The uneven distribution was the actual problem, but I found the solution
> for that (changing the epsilon) so now there's no problem at all...
As the distribution exactly uses the uv-points which I it is the same
problem. In regards to the formula u,v,w are exactly symmetric (as long as
you do not chang epislon1).
lain simple regulare space.
>
> There is a white space in the messages I send. If it's not there when
> they arrive, then Outlook Express must somehow remove them. :(
>
evil program
- Micha
--
http://objects.povworld.org - the POV-Ray Objects Collection
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From: Micha Riser
Subject: Re: I really really want n-sided bezier patches...
Date: 23 Aug 2002 12:46:50
Message: <3d6666fa@news.povray.org>
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Rune wrote:
> A few more comments...
>
> I did a new comparing of the patch with and without the normalisation
> property, and there is indeed a quite visible difference, so I think
> it's a good thing it was implemented, even though it slows down the
> calculations.
it just doubled the formula's length..
>
> And about optimisation - the fact that your recursive version passes the
> points along doesn't mean that they are only calculated once. They are
> calculated twize, because each edge is shared by two triangles, and when
> you divide an edge in two, you do it for both triangles.
That's true indeed.
--
http://objects.povworld.org - the POV-Ray Objects Collection
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From: Rune
Subject: Re: I really really want n-sided bezier patches...
Date: 23 Aug 2002 14:41:01
Message: <3d6681bd@news.povray.org>
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Micha Riser wrote:
>> As I assumed, it was something with how the w
>> value was calculated. Apparently, if 1-2*u*v is
>> smaller than 1.0, then no division should happen
>> at all (or a division by 1). I found out by
>> coincidence more or less, so don't ask me why...
>
> NOO! What you get is no longer a bezier patch!
> You lose the C-1 continuity at the borders!
Argh, sighhhh.
That's what I get from changing variables at random...
Maybe there's still hope. With only a 200% increase in parse time we
could calculate each point three times, each with a different edge being
the w edge. Then average those three points.
What? What's wrong with that??
...
Rune
--
3D images and anims, include files, tutorials and more:
rune|vision: http://runevision.com (updated July 12)
POV-Ray Ring: http://webring.povray.co.uk
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From: Micha Riser
Subject: Re: I really really want n-sided bezier patches...
Date: 23 Aug 2002 18:32:26
Message: <3d66b7fa@news.povray.org>
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Rune wrote:
> Maybe there's still hope. With only a 200% increase in parse time we
> could calculate each point three times, each with a different edge being
> the w edge. Then average those three points.
>
> What? What's wrong with that??
>
> ...
Try it, I could not bring this idea working. I do not really understand
what causes the different sizes of the triangles.
--
http://objects.povworld.org - the POV-Ray Objects Collection
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Micha Riser wrote:
> Rune wrote:
>> Maybe there's still hope. With only a 200% increase
>> in parse time we could calculate each point three
>> times, each with a different edge being the w edge.
>> Then average those three points.
>>
>> What? What's wrong with that??
>>
>> ...
>
> Try it, I could not bring this idea working. I do
> not really understand what causes the different
> sizes of the triangles.
I think I have a solution, and this time it might even work correctly...
;)
I did some #debug work and I found out that the w value is indeed
"skewed" and that changing the epsilon1 value to 1.0 makes it
"straight".
However, when u, v and w are all straight, the patch does not join up
smoothly with other patches. Making any one of the u, v or w value
skewed makes it smooth again, and it doesn't matter which of them it is.
So instead of having one of them completely skewed, I tried making all
of them 1/3 skewed and 2/3 straight. It seems to work. The patch seems
to be smooth, and the triangles are distributed evenly. Also, there is
practically no slow-down, as the averaging part is done to the u, v and
w values before the actual points are calculated.
I'll post the code when it's cleaned up.
Rune
--
3D images and anims, include files, tutorials and more:
rune|vision: http://runevision.com (updated July 12)
POV-Ray Ring: http://webring.povray.co.uk
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From: Micha Riser
Subject: Re: I really really want n-sided bezier patches...
Date: 26 Aug 2002 15:13:56
Message: <3d6a7df3@news.povray.org>
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>
> I think I have a solution, and this time it might even work correctly...
> ;)
>
OK, sound good. I will have a look at it when I get some time. I will try
the 5-sided (and eventually the 6-sided) then too.
- Micha
--
http://objects.povworld.org - the POV-Ray Objects Collection
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Micha Riser wrote:
> OK, sound good. I will have a look at it when I get
> some time. I will try the 5-sided (and eventually
> the 6-sided) then too.
Sounds good! :)
Rune
--
3D images and anims, include files, tutorials and more:
rune|vision: http://runevision.com (updated July 12)
POV-Ray Ring: http://webring.povray.co.uk
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in news:3d6571f8$1@news.povray.org Rune wrote:
> Actually, uv-mapping should be easy to make, as the whole patch seems to
> be based on uv coordinates in the first place.
More or less falling in the middle of a thread, just back from the UK
Gathering. Just before I left, I plugged Micha's equations into param.inc,
it produces mesh2 and does uv-mapping, not sure though if the mapping is
as you want it.
Ingo
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ingo wrote:
> More or less falling in the middle of a thread,
> just back from the UK Gathering. Just before I
> left, I plugged Micha's equations into param.inc,
> it produces mesh2 and does uv-mapping, not sure
> though if the mapping is as you want it.
I'd like to have a look. I already made the code generate a mesh2 and
for the mapping I plan to work on some non-linear mapping, but to see
alternative solutions can never hurt. There might be some things that
could be optimized or something like that. :)
Rune
--
3D images and anims, include files, tutorials and more:
rune|vision: http://runevision.com (updated July 12)
POV-Ray Ring: http://webring.povray.co.uk
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in news:3d6bd332$1@news.povray.org Rune wrote:
> I'd like to have a look.
Posted the scene as a follow-up to Micha's first post in p.t.s-f
Newsgroups: povray.text.scene-files
Subject: Re: 3-sided bezier
From: ingo <ing### [at] home nl>
Message-ID: <Xns### [at] povrayorg>
Date: 27 Aug 2002 16:28:33 -0400
Xref: news.povray.org povray.text.scene-files:3199
Ingo
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