Has someone looked in the sphere_sweep problem that was previously reported
in :

http://news.povray.org/web.44779e5a358a67bc5c947f990%40news.povray.org

The last version of povray that correctly rendered the file mentioned
in the bug report was compiled v3.5 on Linux.


Thanks -
Tom

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"tom" ha scritto 
> 
> Has someone looked in the sphere_sweep problem that was previously reported
> in :
> 
> http://news.povray.org/web.44779e5a358a67bc5c947f990%40news.povray.org
> 
> The last version of povray that correctly rendered the file mentioned
> in the bug report was compiled v3.5 on Linux.
> 
> 

The problem is that the intersection between a planar speresweep and a ray 
orthogonal to the plane is ill-conditioned. The equation is a polynomial
that is a perfect square:

    p(d) = p2(d) * p2(d)

meaning that it is always non negative and zero only on the surface.

And every root is multiple and sturm's sequences should be special cased,
not mentioning that bisection is pratically useless...

I have an implementation fixing these and other problems, just waiting
for the sources to become open source.

Massimo

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Massimo Valentini <not### [at] vailableinvalid> wrote:
> I have an implementation fixing these and other problems, just waiting
> for the sources to become open source.

  Why can't you publish your fixes? There's a chance they will be
implemented in pov3.7 before final release.

-- 
                                                          - Warp

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"Warp" ha scritto > Massimo Valentini > 
>   Why can't you publish your fixes? There's a chance they will be
> implemented in pov3.7 before final release.
> 

I'm not going to publish anything before pov4.
Hopefully the Pov team will fix this trivial 
bug anyway.

Massimo

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Massimo Valentini <not### [at] vailableinvalid> wrote:
> I'm not going to publish anything before pov4.

  Then you'll have to wait a rather long time.

  Just out of curiosity: Why not? Don't you want to contribute?

-- 
                                                          - Warp

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"Warp" ha scritto 
> 
>   Then you'll have to wait a rather long time.
> 
>   Just out of curiosity: Why not? Don't you want to contribute?
> 

I think that describing when and (at least partly) why some
code misbehaves IS contributing.

Massimo

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Massimo Valentini <not### [at] vailableinvalid> wrote:
> I think that describing when and (at least partly) why some
> code misbehaves IS contributing.

  If you have a solution proposal, why don't post it?

-- 
                                                          - Warp

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"Warp" ha scritto 
> 
>   If you have a solution proposal, why don't post it?
> 

Because, hopefully, it is not necessary. 
If otherwise it will be useful I'll post it, but then 
you'll have to wait a rather long time.

Massimo

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Massimo Valentini <not### [at] vailableinvalid> wrote:
> "Warp" ha scritto 
> > 
> >   If you have a solution proposal, why don't post it?
> > 

> Because, hopefully, it is not necessary. 
> If otherwise it will be useful I'll post it, but then 
> you'll have to wait a rather long time.

  I must admit I'm completely puzzled. You said in your first post that
you have an implementation. Of course it's your right to refuse to publish
it, but your reason for that just escapes me.

  Well, whatever. If you don't want to see the problem fixed, then don't.

-- 
                                                          - Warp

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Warp wrote:
>   Well, whatever. If you don't want to see the problem fixed, then don't.

Massimo has the idea that he won't contribute anything to POV because he
feels we should be GPL'd or something similar ... of course, his attitude
is only holding up such a transition. He has privately told me that he
disagrees with our current licensing; you may also note he withdrew from
assisting us in the private testing group some time back.

Massimo: how about you put your money where your mouth is? ... suppose we
said to you "here is the 3.7 codebase; these are the parts that can be
OSS'd, and these are the parts that have to be cut out and re-written. Make
a 4.0 framework containing the open-source-able code with the rest stubbed
out. Put all your contributions under the GPL3 and we'll do the same."

If you *really* want to see a GPL'd 4.0 then you'll do it. Since at the
moment lack of manpower is the only issue holding us back from doing
exactly that. Internally we are comfortable with the GPL3. We wish to
create a 4.0 framework that contains as much of the existing code as we can
bring across and then open it up to the public to assist in filling in the
code that has to be re-written.

-- Chris

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