"W?odzimierz ABX Skiba" <abx### [at] babilonorg> wrote in message
news:d091eu092vqvbnn84edd8h1hv63t6bd27h@4ax.com...

> void Compute_Min_Max_B_Spline(DBL p0,p1,p2,p3,*minp,*maxp)
> {
>   DBL a,b,c,delta;
>
>   // first derivative of spline equation is
>   // 1/2*(-p0+3*p1-3*p2+p3)*t^2+(p0-2*p1+p2)*t-1/2*p0+1/2*p2
>
>   a=1/2*(-p0+3*p1-3*p2+p3);
>   b=p0-2*p1+p2;
>   c=(-p0+p2)/2;
>   d=b*b-4*a*c;
>   if ((d<0)||(a==0)) // for unexpected errors return the biggest bbox
>     {
>       t1=0;
>       t2=1;
>     }
>   else
>     {
>       // parameter for extremas
>       t1=(-b-sqrt(d))/(2*a);
>       t2=(-b+sqrt(d))/(2*a);
>       // parameter should be clipped to visible part of segment
>       t1=min(max(t1,0),1);
>       t2=min(max(t2,0),1);
>     }
>   t1 = Compute_B_Spline_Value(t1);
>   t2 = Compute_B_Spline_Value(t2);
>   minp = min( t1, t2 );
>   maxp = max( t1, t2 );
> }
>
> DBL Compute_Catmull_Rom_Spline_Value(DBL t)
> {
>   // should be best to code this using already defined Catmull_Rom_Matrix
>   return
((2*p1)+(-p0+p2)*t+(2*p0-5*p1+4*p2-p3)*t^2+(-p0+3*p1-3*p2+p3)*t^3)/2;
> }
>
> void Compute_Min_Max_Catmull_Rom_Spline(DBL p0,p1,p2,p3,*minp,*maxp)
> {
>   DBL a,b,c,delta;
>
>   // first derivative of spline equation is
>   // -1/2*p0+1/2*p2+(2*p0-5*p1+4*p2-p3)*t+3/2*(-p0+3*p1-3*p2+p3)*t^2
>
>   a=3*(-p0+3*p1-3*p2+p3)/2;
>   b=2*p0-5*p1+4*p2-p3;
>   c=(-p0+p2)/2;
>   d=b*b-4*a*c;
>   if ((d<0)||(a==0)) // for unexpected errors return the biggest bbox
>     {
>       t1=0;
>       t2=1;
>     }
>   else
>     {
>       // parameter for extremas
>       t1=(-b-sqrt(d))/(2*a);
>       t2=(-b+sqrt(d))/(2*a);
>       // parameter should be clipped to visible part of segment
>       t1=min(max(t1,0),1);
>       t2=min(max(t2,0),1);
>     }
>   t1 = Compute_Catmull_Rom_Spline_Value(t1);
>   t2 = Compute_Catmull_Rom_Spline_Value(t2);
>   minp = min( t1, t2 );
>   maxp = max( t1, t2 );
> }


Two remarks:
1) the only difference between procedures Compute_Min_Max_B_Spline and
Compute_Min_Max_Catmull_Rom_Spline is their polynomial coefficients a,b,c,d,
maybe it's better to put this common part in a separate procedure;

2) the curve can possibly reach its min/max at its ends, when t=0 and t=1.

Regards,

Gleb

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On Tue, 14 May 2002 19:15:10 +0100, "Gleb" <gk1### [at] sotonacuk> wrote:
> Two remarks:
> 1) the only difference between procedures Compute_Min_Max_B_Spline and
> Compute_Min_Max_Catmull_Rom_Spline is their polynomial coefficients a,b,c,d,
> maybe it's better to put this common part in a separate procedure;

That was obvious conclusion when I wrote this stuff, moreover it could be
probably written in general form with one matrix as parameter (valid also
for linear spline) but I had no access to compiler and net to make it so I
wrote simplest form I could at that moment.

> 2) the curve can possibly reach its min/max at its ends, when t=0 and t=1.

so whole discussion has no sense ? :-)

ABX

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"W?odzimierz ABX Skiba" <abx### [at] babilonorg> wrote in message
news:e6u3eu0h9scfphre7glpfvadu0bbsvbikt@4ax.com...
> > 2) the curve can possibly reach its min/max at its ends, when t=0 and
t=1.
>
> so whole discussion has no sense ? :-)

Of course it has :)
The only thing to fix this is to check that after calculating the local
min/max values for x,y,z.

Post a reply to this message

wrote:
>  return local: news.povray.org/e3piut8anmf4cli4pnfmstadgc3nleqvb2@4ax.com

I can still cause crash with RC5. Just a few Render/Stop/Render/Stop cycles.

> not works as (I) expected
>  splines:      news.povray.org/m4f7cug9ch19jbve8m8prf4vl8ima0rsma@4ax.com
>  bounding:     news.povray.org/2g0dcu8kasg84pqde8hdq9d60nkoa1cvka@4ax.com
>  evaluate msg: news.povray.org/4nhfduk9gon9m76s6f6vu3k8gsjf7rrdjp@4ax.com

Any chance to see 'Known bugs' list. None of listed is fixed but I don't want
bother too much - I just don't know what is current status of those reports.

ABX

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<abx### [at] babilonorg> wrote:

>>  return local: news.povray.org/e3piut8anmf4cli4pnfmstadgc3nleqvb2@4ax.com
>
> I can still cause crash with RC5. Just a few Render/Stop/Render/Stop cycles.

Works fine here.

>> not works as (I) expected
>>  splines:      news.povray.org/m4f7cug9ch19jbve8m8prf4vl8ima0rsma@4ax.com

The report is incomplete.  The behavior you reported that could be reproduced
without a scene has been fixed and for the rest an example is needed.

>>  bounding:     news.povray.org/2g0dcu8kasg84pqde8hdq9d60nkoa1cvka@4ax.com

Won't be fixed in 3.5 as previously explained.

>>  evaluate msg: news.povray.org/4nhfduk9gon9m76s6f6vu3k8gsjf7rrdjp@4ax.com

Not a bug.

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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On Mon, 20 May 2002 15:21:58 +0200, "Thorsten Froehlich" <tho### [at] trfde>
wrote:
> > >  return local: news.povray.org/e3piut8anmf4cli4pnfmstadgc3nleqvb2@4ax.com
> >
> > I can still cause crash with RC5. Just a few Render/Stop/Render/Stop cycles.
>
> Works fine here.

Works fine here for nearly every render. But crashes after a few cycles
Render/Stop/Render/.../Render/Stop without finishing rendering.

> > > not works as (I) expected
> > >  splines:      news.povray.org/m4f7cug9ch19jbve8m8prf4vl8ima0rsma@4ax.com
>
> The report is incomplete.  The behavior you reported that could be reproduced
> without a scene has been fixed and for the rest an example is needed.

What is wrong in example I posted in
pckkduod909g1736lrlm75pakanfm5rs3u@4ax.com ?


> > >  bounding:     news.povray.org/2g0dcu8kasg84pqde8hdq9d60nkoa1cvka@4ax.com
>
> Won't be fixed in 3.5 as previously explained.

Previously was explained it won't be fixed "unless someone comes up with code
to determine the bounding box of a Catmull-Rom spline segment". What is wrong
with code I posted in ftb1euon0h27vscfcjmfjd1cuqlbmvrluh@4ax.com ?

ABX

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Skiba <abx### [at] babilonorg>  wrote:

> Works fine here for nearly every render. But crashes after a few cycles
> Render/Stop/Render/.../Render/Stop without finishing rendering.

But then it can be a million things and doesn't even have to do anything with
macros.  If it can't be reproduced, I am afraid it won't get fixed ... of
course, what would really help is an always crashing example.

> What is wrong in example I posted in
> pckkduod909g1736lrlm75pakanfm5rs3u@4ax.com ?

Nothing except thata I didn't remember this particular example.  I think I
have found that problem now and assume it was the only one left from your list
of spline problems?

> Previously was explained it won't be fixed "unless someone comes up with code
> to determine the bounding box of a Catmull-Rom spline segment". What is wrong
> with code I posted in ftb1euon0h27vscfcjmfjd1cuqlbmvrluh@4ax.com ?

To quote you in that thread:
>- I did it completly without parser/compiler so it is not verified for syntax
>   (in particular I wrote something in C long time ago and I don't remeber
>   referencing rules)
> - I was tired (but enthusiastic about it)
> - I hope it isn't too late and used spline equations are correct
> - I added some helper functions and made note how it could be improved by
>   adding Bound union of boxes to additionaly optimize intersection test

Essentially, my ikdea of some providing code was "fully tested" code, not code
I would need to debug myself and that would possibly need several iterations
until it completely works.  Without having time for it that is really the only
thing that could have been used.  Anyway, it is probably too late now.

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

Post a reply to this message

On Tue, 21 May 2002 18:14:04 +0200, "Thorsten Froehlich" <tho### [at] trfde>
wrote:
> > Works fine here for nearly every render. But crashes after a few cycles
> > Render/Stop/Render/.../Render/Stop without finishing rendering.
>
> But then it can be a million things and doesn't even have to do anything with
> macros.  If it can't be reproduced, I am afraid it won't get fixed ... of
> course, what would really help is an always crashing example.

Unfortunatelly it is only example I have :-(

> > What is wrong in example I posted in
> > pckkduod909g1736lrlm75pakanfm5rs3u@4ax.com ?
>
> Nothing except thata I didn't remember this particular example.  I think I
> have found that problem now and assume it was the only one left from your list
> of spline problems?

Great!

> > Previously was explained it won't be fixed "unless someone comes up with code
> > to determine the bounding box of a Catmull-Rom spline segment". What is wrong
> > with code I posted in ftb1euon0h27vscfcjmfjd1cuqlbmvrluh@4ax.com ?
>
> Essentially, my ikdea of some providing code was "fully tested" code

I see, so I will test this when sources will be released. I hope with small
effort it will be possible to compile 3.5 with djgpp or free borland release.

> Anyway, it is probably too late now.

Sounds promising :-)

ABX

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Thorsten Froehlich wrote:
> Essentially, my ikdea of some providing code was "fully tested" code, not
> code I would need to debug myself and that would possibly need several
> iterations
> until it completely works.  Without having time for it that is really the
> only
> thing that could have been used.  Anyway, it is probably too late now.

Can ABX's code be included after the final release of 3.5?
-- 
Felix Wiemann

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In article <3ceb84d3@news.povray.org> , Felix Wiemann <Fel### [at] gmxnet>
wrote:

> Can ABX's code be included after the final release of 3.5?

I am sure that a few month after the initial 3.5 release there will be some
kind of bugfix release to include all the known bugs for which we get fixes
for from users and for the newly discovered bugs that we fix ourselves.

Also, as new compilers become available, we will of course keep POV-Ray
up-to-date as far as those are concerned in order to get the best performance
available.

Note however that we won't promise that the source code will be available on
day one of the official release for all platforms.  Only after the release
there will be time to make sure it can easily be compiled and the files are
complete and so on...

    Thorsten

____________________________________________________
Thorsten Froehlich
e-mail: mac### [at] povrayorg

I am a member of the POV-Ray Team.
Visit POV-Ray on the web: http://mac.povray.org

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