sorry if the list is known
here is summary how my lately reports (and confirmations) work with RC4

POV 3.5 RC4 icl on WinNT Sp 6 PII 233 with 128 MB

crash

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

not works as (I) expected

  splines:      news.povray.org/m4f7cug9ch19jbve8m8prf4vl8ima0rsma@4ax.com
                when point is added then type of spline is overwritten
                so bottom, second from right is wrong
  bounding:     news.povray.org/2g0dcu8kasg84pqde8hdq9d60nkoa1cvka@4ax.com
                sphere-sweeps are still clipped
  evaluate msg: news.povray.org/4nhfduk9gon9m76s6f6vu3k8gsjf7rrdjp@4ax.com
                end of paragraph makes suggested value of evaluate valid
                for report of next evaluate

ABX

Post a reply to this message

W³odzimierz ABX Skiba wrote:
> sorry if the list is known
> here is summary how my lately reports (and confirmations) work with
> RC4
> 
> POV 3.5 RC4 icl on WinNT Sp 6 PII 233 with 128 MB
> 
> crash
> 
>   return local:
>   news.povray.org/e3piut8anmf4cli4pnfmstadgc3nleqvb2@4ax.com
> 
> not works as (I) expected
> 
>   splines:     
>   news.povray.org/m4f7cug9ch19jbve8m8prf4vl8ima0rsma@4ax.com
>                 when point is added then type of spline is overwritten
>                 so bottom, second from right is wrong
>   bounding:    
>   news.povray.org/2g0dcu8kasg84pqde8hdq9d60nkoa1cvka@4ax.com
>                 sphere-sweeps are still clipped
>   evaluate msg:
>   news.povray.org/4nhfduk9gon9m76s6f6vu3k8gsjf7rrdjp@4ax.com
>                 end of paragraph makes suggested value of evaluate
>                 valid for report of next evaluate

Does any of these bugs still need confirmation?
Could you please give full http:// links in future? My newsreader can't 
open them directly because it thinks it's a mail address or MID.
-- 
Felix Wiemann

Post a reply to this message

On Wed, 08 May 2002 20:11:17 +0200, Felix Wiemann <Fel### [at] gmxnet>
wrote:
> Does any of these bugs still need confirmation?

I think non of "not works as expected" was here confirmed hovewer. Crash was
confirmed by Chris Hormann.

> Could you please give full http:// links in future? My newsreader can't 
> open them directly because it thinks it's a mail address or MID.

It is Messege ID! It works fine with both prefixes news:// and http://
Usually I add http:// hovewer this time I removed it intentionally becouse of
idea of justification.

ABX

Post a reply to this message

W³odzimierz ABX Skiba wrote:
> It is Messege ID! It works fine with both prefixes news:// and http://
> Usually I add http:// hovewer this time I removed it intentionally
> becouse of idea of justification.

Sorry, I didn't notice that. Maybe it's better if the news.povray.org/ 
in front of the message ID is removed. Or it's my newsreader's fault. I 
don't know.
-- 
Felix Wiemann

Post a reply to this message

In article <2dfidu08man5vk2i3it03lms1j9isg8jjv@4ax.com> , W„odzimierz ABX 
Skiba <abx### [at] babilonorg>  wrote:

>   splines:      news.povray.org/m4f7cug9ch19jbve8m8prf4vl8ima0rsma@4ax.com
>                 when point is added then type of spline is overwritten
>                 so bottom, second from right is wrong

I don't get what you want to say in the sentence above.

>   bounding:     news.povray.org/2g0dcu8kasg84pqde8hdq9d60nkoa1cvka@4ax.com
>                 sphere-sweeps are still clipped

Yes, and this will remain the way it is unless someone comes up with code to
determine the bounding box of a Catmull-Rom spline segment.  It turns out the
original sphere_sweep code simply adds a bit to the control point bounding
box.  The problem appears only for Catmull-Rom splines because they may exceed
their control points which the code uses to find the bounding...

>   evaluate msg: news.povray.org/4nhfduk9gon9m76s6f6vu3k8gsjf7rrdjp@4ax.com
>                 end of paragraph makes suggested value of evaluate valid
>                 for report of next evaluate

I don't get what is supposed to be wrong here?!?

    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 Thu, 09 May 2002 11:56:33 +0200, "Thorsten Froehlich" <tho### [at] trfde>
wrote:
> >   splines:      news.povray.org/m4f7cug9ch19jbve8m8prf4vl8ima0rsma@4ax.com
> >                 when point is added then type of spline is overwritten
> >                 so bottom, second from right is wrong
>
> I don't get what you want to say in the sentence above.

Sorry if it is caused by me English. I try to write it again and show shorter
example: when I copy spline identifier and add point in the same time then I
expect that new spline will have the same type and new point. Point is added
but type of spline is overwritten. Example:

  #macro Draw(Spline,Color)
    #local c=0;
    #while (c<1)
      sphere{Spline(c) .1 translate 3*z pigment{Color} finish{ambient 1}}
      #local c=c+.01;
    #end
  #end
  background{1}
  #local S=spline{ cubic_spline -1 5*x 0 x 1 y 2 5*y }
  Draw(S,red 1)
  Draw(spline{S 0.5 x+y},blue 1)

> >   bounding:     news.povray.org/2g0dcu8kasg84pqde8hdq9d60nkoa1cvka@4ax.com
>
> Yes, and this will remain the way it is unless someone comes up with code

I see.

> >   evaluate msg: news.povray.org/4nhfduk9gon9m76s6f6vu3k8gsjf7rrdjp@4ax.com
> >                 end of paragraph makes suggested value of evaluate valid
> >                 for report of next evaluate
>
> I don't get what is supposed to be wrong here?!?

Nothing is wrong. The problem is that it is just less readable when suggested
values are connected in this paragraph with evaluated values of next evaluate.
Just problem of place of "\n" placing. But if it is caused by internall
wraping system for all messages then probably nothing to worry about - values
are (I suppose) correct.

ABX

Post a reply to this message

"Thorsten Froehlich" <tho### [at] trfde> wrote in message
news:3cda47d8@news.povray.org...
> Yes, and this will remain the way it is unless someone comes up with code
to
> determine the bounding box of a Catmull-Rom spline segment.  It turns out
the
> original sphere_sweep code simply adds a bit to the control point bounding
> box.  The problem appears only for Catmull-Rom splines because they may
exceed
> their control points which the code uses to find the bounding...

If there is already code for the bounding box of a Bezier spline segment,
is it difficult to internally convert Catmull-Rom spline segment into Bezier
one
(to find the two additional control points) and to use it?

Gleb

Post a reply to this message

In article <3cda78bf$1@news.povray.org> , "Gleb" <gk1### [at] sotonacuk> wrote:

> If there is already code for the bounding box of a Bezier spline segment,

In case you did not notice, we are talking about too tight bounding here.  So
this is not the question.  All sphere_sweeps are bounded for speed reasons -
and you don't want to render any sphere_sweep without bounding!

> is it difficult to internally convert Catmull-Rom spline segment into Bezier
> one (to find the two additional control points) and to use it?

A Catmull-Rom spline can extend "beyond" its control points.  It is not a
matter of converting to some other spline type.  The problem is to determine
the bounds of a Catmull-Rom spline segment by just looking at the control
points, which is simply not possible due to the nature of this spline type.

To clarify my original point:

This is not going to be fixed because nobody in the team has the time to look
into this mess.  Making wild suggestions won't help ;-)

Only plain and simple source code, based on the available sphere_sweep code
that can be found in MegaPOV, if contributed by someone _soon_, will fix the
problem in the initial 3.5 release.  The code was already been broken in the
original patch :-(  Its author apparently did not know a good way how to fix
it either, so don't expect magic from us!

    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

Post a reply to this message

Thorsten Froehlich wrote:
> In case you did not notice, we are talking about
> too tight bounding here.  So this is not the question.

Perhaps he did notice and perhaps he has a valid point. You are always
very quick to reject other people's suggestions as being nonsense or
irrelevant.

Anyway, please see my post in povray.beta-test.binaries for a suggestion
for bounding which is inspired my Gleb's message.

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:  http://rsj.mobilixnet.dk (updated Apr 14)
POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Ring:  http://webring.povray.co.uk

Post a reply to this message

Thorsten Froehlich wrote:
> 
> In article <2dfidu08man5vk2i3it03lms1j9isg8jjv@4ax.com> , W„odzimierz ABX
> Skiba <abx### [at] babilonorg>  wrote:
> 
> >   splines:      news.povray.org/m4f7cug9ch19jbve8m8prf4vl8ima0rsma@4ax.com
> >                 when point is added then type of spline is overwritten
> >                 so bottom, second from right is wrong
> 
> I don't get what you want to say in the sentence above.
> 
> >   bounding:     news.povray.org/2g0dcu8kasg84pqde8hdq9d60nkoa1cvka@4ax.com
> >                 sphere-sweeps are still clipped
> 
> Yes, and this will remain the way it is unless someone comes up with code to
> determine the bounding box of a Catmull-Rom spline segment.  It turns out the
> original sphere_sweep code simply adds a bit to the control point bounding
> box.  The problem appears only for Catmull-Rom splines because they may exceed
> their control points which the code uses to find the bounding...

I have not looked very closely at this, but I don't
think it that it should be very difficult to find an
analytical solution to this.

As I understand it, there should be 3 cubic polynomials
that controls the x, y and z components for each segment.

Just differentiate these (to quadratic polynomials) and
solve for zero to find the max and min points of the
cubic polynomials. The values of the cubic polynomials
at these points will give the components for the
bounding box.

If any of the cubic polynomials has no real roots, then
I think that values at the endpoints of the cubic will
polynomials give the max and min points for the spline
segment.


Tor Olav

Post a reply to this message

"Thorsten Froehlich" <tho### [at] trfde> wrote in message
news:3cda9ef6@news.povray.org...
> In article <3cda78bf$1@news.povray.org> , "Gleb" <gk1### [at] sotonacuk> wrote:
>
> A Catmull-Rom spline can extend "beyond" its control points.  It is not a
> matter of converting to some other spline type.  The problem is to
determine
> the bounds of a Catmull-Rom spline segment by just looking at the control
> points, which is simply not possible due to the nature of this spline
type.
>
> To clarify my original point:
>
> This is not going to be fixed because nobody in the team has the time to
look
> into this mess.  Making wild suggestions won't help ;-)
>
> Only plain and simple source code, based on the available sphere_sweep
code
> that can be found in MegaPOV, if contributed by someone _soon_, will fix
the
> problem in the initial 3.5 release.  The code was already been broken in
the
> original patch :-(  Its author apparently did not know a good way how to
fix
> it either, so don't expect magic from us!

Why not ;)


Thank you for pointing the source,
it would be easier to explain what I mean.

In the source mentioned every spline segment
of this scaring Catmull-Rom spline
is internally represented as four polynomial coefficients, say
a3, a2, a1 and a0. Actual curve segment is calculated
as a3*t^3+a2*t^2+a1*t+a0. And every such a segment has two
control points at its ends from original definition.
And of course, the curve can escape the set of original control points.
What I'm talking about is that there are two "additional control points"
hidden inside this polynomial, because the same beast can also be
represented as
a3*t^3+a2*t^2+a1*t+a0 = A*(1-t)^3+3*B*t*(1-t)^2+3*C*t^2*(1-t)+D*t^3
which is the other scaring thing, Bezier spline segment.
In this form(for exactly the same curve) we have four control points,
A, B, C, D, where A and D are the same as the original Catmull-Rom spline
segment control points, but we also have two additional control points,
B and C. And our segment now can't escape the convex hull
of that set of the four control points.
And if there is already working code for calculating the bounding box
for Bezier spline segments, we can feed it with these four control
points - that's all.

On the other hand the method suggested by Tor Olav may be even better
(more precise).


Regards,

Gleb

Post a reply to this message

On Thu, 09 May 2002 18:08:14 +0200, "Thorsten Froehlich" <tho### [at] trfde>
wrote:
> Only plain and simple source code, based on the available sphere_sweep code
> that can be found in MegaPOV, if contributed by someone _soon_, will fix the
> problem in the initial 3.5 release.  The code was already been broken in the
> original patch :-(  Its author apparently did not know a good way how to fix
> it either, so don't expect magic from us!

I have not noticed any announcement that somebody started to code this so I
used some part of my night to prepare code. Some notes:
- 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
- I used MEGAPOV 0.6a source

// *******************************************************************

DBL Compute_B_Spline_Value(DBL t)
{
  // should be best to code this using already defined B_Matrix
  return 1/6*(-p0+3*p1-3*p2+p3)*t^3
        +1/2*(p0-2*p1+p2)*t^2
        +1/2*(-p0+p2)*t
        +1/6*(p0+4*p1+p2);
}

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 );
}

void Compute_Sphere_Sweep_BBox(Sphere_Sweep)
SPHERE_SWEEP *Sphere_Sweep;
{
  VECTOR mins,maxs,segmins,segmaxs;
  int i,number_of_segments;
  DBL min_radius,max_radius;

  if( Sphere_Sweep->Interpolation == LINEAR_SPLINE)
    number_of_segments=Sphere_Sweep->Num_Modeling_Spheres-1;
  else
    number_of_segments=Sphere_Sweep->Num_Modeling_Spheres-3;

  // set initial value for general bbox extents
  // to one of "visible" control points of object
  Assign_Vector( mins , Sphere_Sweep->Modeling_Sphere[1].Center );
  Assign_Vector( maxs , Sphere_Sweep->Modeling_Sphere[1].Center );

  for (i = 0; i < number_of_segments; i++)
    {
      // set initial value for local bbox extents
      // to one of "visible" control points of segment
      Assign_Vector( segmins , Sphere_Sweep->Modeling_Sphere[i+1].Center );
      Assign_Vector( segmaxs , Sphere_Sweep->Modeling_Sphere[i+1].Center );

      switch (Sphere_Sweep->Interpolation)
      {
         case B_SPLINE:
           Compute_Min_Max_B_Spline(
             Sphere_Sweep->Modeling_Sphere[I  ].Center[X],
             Sphere_Sweep->Modeling_Sphere[i+1].Center[X],
             Sphere_Sweep->Modeling_Sphere[i+2].Center[X],
             Sphere_Sweep->Modeling_Sphere[i+3].Center[X],
             segmins[X],
             segmaxs[X]
           )
           Compute_Min_Max_B_Spline(
             Sphere_Sweep->Modeling_Sphere[I  ].Center[Y],
             Sphere_Sweep->Modeling_Sphere[i+1].Center[Y],
             Sphere_Sweep->Modeling_Sphere[i+2].Center[Y],
             Sphere_Sweep->Modeling_Sphere[i+3].Center[Y],
             segmins[Y],
             segmaxs[Y]
           )
           Compute_Min_Max_B_Spline(
             Sphere_Sweep->Modeling_Sphere[I  ].Center[Z],
             Sphere_Sweep->Modeling_Sphere[i+1].Center[Z],
             Sphere_Sweep->Modeling_Sphere[i+2].Center[Z],
             Sphere_Sweep->Modeling_Sphere[i+3].Center[Z],
             segmins[Z],
             segmaxs[Z]
           )
           Compute_Min_Max_B_Spline(
             Sphere_Sweep->Modeling_Sphere[I  ].Radius,
             Sphere_Sweep->Modeling_Sphere[i+1].Radius,
             Sphere_Sweep->Modeling_Sphere[i+2].Radius,
             Sphere_Sweep->Modeling_Sphere[i+3].Radius,
             min_radius,
             max_radius
           )
         break;
         case CATMULL_ROM_SPLINE:
           Compute_Min_Max_Catmull_Rom_Spline(
             Sphere_Sweep->Modeling_Sphere[I  ].Center[X],
             Sphere_Sweep->Modeling_Sphere[i+1].Center[X],
             Sphere_Sweep->Modeling_Sphere[i+2].Center[X],
             Sphere_Sweep->Modeling_Sphere[i+3].Center[X],
             segmins[X],
             segmaxs[X]
           )
           Compute_Min_Max_Catmull_Rom_Spline(
             Sphere_Sweep->Modeling_Sphere[I  ].Center[Y],
             Sphere_Sweep->Modeling_Sphere[i+1].Center[Y],
             Sphere_Sweep->Modeling_Sphere[i+2].Center[Y],
             Sphere_Sweep->Modeling_Sphere[i+3].Center[Y],
             segmins[Y],
             segmaxs[Y]
           )
           Compute_Min_Max_Catmull_Rom_Spline(
             Sphere_Sweep->Modeling_Sphere[I  ].Center[Z],
             Sphere_Sweep->Modeling_Sphere[i+1].Center[Z],
             Sphere_Sweep->Modeling_Sphere[i+2].Center[Z],
             Sphere_Sweep->Modeling_Sphere[i+3].Center[Z],
             segmins[Z],
             segmaxs[Z]
           )
           Compute_Min_Max_Catmull_Rom_Spline(
             Sphere_Sweep->Modeling_Sphere[I  ].Radius,
             Sphere_Sweep->Modeling_Sphere[i+1].Radius,
             Sphere_Sweep->Modeling_Sphere[i+2].Radius,
             Sphere_Sweep->Modeling_Sphere[i+3].Radius,
             min_radius,
             max_radius
           )
         break;
         case LINEAR_SPLINE:
           segmins[X] = min( segmins[X],
                        Sphere_Sweep->Modeling_Sphere[i].Center[X] );
           segmins[Y] = min( segmins[Y], 
                        Sphere_Sweep->Modeling_Sphere[i].Center[Y] );
           segmins[Z] = min( segmins[Z], 
                        Sphere_Sweep->Modeling_Sphere[i].Center[Z] );
           segmaxs[X] = max( segmins[X], 
                        Sphere_Sweep->Modeling_Sphere[i].Center[X] );
           segmaxs[Y] = max( segmins[Y], 
                        Sphere_Sweep->Modeling_Sphere[i].Center[Y] );
           segmaxs[Z] = max( segmins[Z], 
                        Sphere_Sweep->Modeling_Sphere[i].Center[Z] );
           max_radius = max( Sphere_Sweep->Modeling_Sphere[i].Radius , 
                        Sphere_Sweep->Modeling_Sphere[i+1].Radius );
         break;
      }

      // consider maximal value of radius
      mins[X] = mins[X]-max_radius;
      mins[Y] = mins[Y]-max_radius;
      mins[Z] = mins[Z]-max_radius;
      maxs[X] = maxs[X]+max_radius;
      maxs[Y] = maxs[Y]+max_radius;
      maxs[Z] = maxs[Z]+max_radius;

      // here you can create box{mins maxs} object as bounding object
      // of current segment - for further optimization union of bounding
      // objects can be used as Bound field of current sphere_sweep

      // compare segment extents with object extents
      mins[X] = min( segmins[X], mins[X] );
      mins[Y] = min( segmins[Y], mins[Y] );
      mins[Z] = min( segmins[Z], mins[Z] );
      maxs[X] = max( segmins[X], maxs[X] );
      maxs[Y] = max( segmins[Y], maxs[Y] );
      maxs[Z] = max( segmins[Z], maxs[Z] );
    }

  Make_BBox_from_min_max(Sphere_Sweep->BBox, mins, maxs);

  if (Sphere_Sweep->Trans != NULL)
    {
      Recompute_BBox(&Sphere_Sweep->BBox, Sphere_Sweep->Trans);
    }
}

// *******************************************************************

ABX

Post a reply to this message

On Tue, 14 May 2002 08:20:18 +0200, W�odzimierz ABX Skiba <abx### [at] babilonorg>
wrote:

> - I was tired (but enthusiastic about it)

yes, I was tired, I found mistake:

>      // consider maximal value of radius
>      mins[X] = mins[X]-max_radius;
>      mins[Y] = mins[Y]-max_radius;
>      mins[Z] = mins[Z]-max_radius;
>      maxs[X] = maxs[X]+max_radius;
>      maxs[Y] = maxs[Y]+max_radius;
>      maxs[Z] = maxs[Z]+max_radius;
>
>      // here you can create box{mins maxs} object as bounding object

should be:

      // consider maximal value of radius
      segmins[X] = segmins[X]-max_radius;
      segmins[Y] = segmins[Y]-max_radius;
      segmins[Z] = segmins[Z]-max_radius;
      segmaxs[X] = segmaxs[X]+max_radius;
      segmaxs[Y] = segmaxs[Y]+max_radius;
      segmaxs[Z] = segmaxs[Z]+max_radius;

      // here you can create box{segmins segmaxs} object as bounding object

ABX

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"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.

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On Wed, 08 May 2002 17:31:03 +0200, W�odzimierz ABX Skiba <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.

> 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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In article <lnkheu0s7p6hned869puv17cdqu3pu8noc@4ax.com>, W�odzimierz ABX Skiba
<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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In article <6pjkeu44jb482k8f95uu964iroa78og3bj@4ax.com> , W„odzimierz ABX 
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

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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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