On Mon, 12 Nov 2001 20:48:44 +0100, Thorsten Froehlich wrote:
> In article <slr### [at] fwicom> , Ron Parker 
><ron### [at] povrayorg>  wrote:
> 
>> Nope, a Win32 stack has a "reserve" size and a "commit" size.  The loader
>> allocates address space for the "reserve" size, but it only actually maps
>> memory for the "commit" size.  It then marks the page just below the
>> commit as Not Present and waits for it to fault.  When it faults, the OS
>> maps another page into the address space
> 
> But it cannot shrink the stack this way.  So once you have a stack that is
> i.e. 100 MB you have to restart the application.  I think the same problem
> exists under Unix.  Unless, of course, you have a system function to shrink
> the stack "manually".

Threads.

Each thread has its own stack allocation.  Kill the render thread and
restart it, and the stack allocation starts over at the "commit" size again.

--
#macro R(L P)sphere{L __}cylinder{L P __}#end#macro P(_1)union{R(z+_ z)R(-z _-z)
R(_-z*3_+z)torus{1__ clipped_by{plane{_ 0}}}translate z+_1}#end#macro S(_)9-(_1-
_)*(_1-_)#end#macro Z(_1 _ __)union{P(_)P(-_)R(y-z-1_)translate.1*_1-y*8pigment{
rgb<S(7)S(5)S(3)>}}#if(_1)Z(_1-__,_,__)#end#end Z(10x*-2,.2)camera{rotate x*90}

Post a reply to this message

"Ken" <tyl### [at] pacbellnet> wrote in message
news:3BEF1927.DABD73B5@pacbell.net...
>
>
>
> The following quote comes straight from the POV-Ray v2.2 docs so it is
> obvious that this limitation has been known for many years now -
>
> "Note: Raising max_trace_level will use more memory and time and it could
> cause the program to crash with a stack overflow error. Values for
> max_trace_level are not restricted, so it can be set to any number as long
> as you have the time and memory."
>

I'm not denying it hasn't been there for a long time... it's just that this is
the first time I've run into it being a problem.  Like I said, I probably read
it a long time ago.

Michael

Post a reply to this message

Fabien Mosen <fab### [at] skynetbe> wrote:
: Out of curiosity, what would you do, render-wise, with a limit of
: 30 000 ???  (or, if you want, even 300).

  Perhaps not 30000, but 300 and more could be necessary to render lots of
semi-transparent objects (eg. lens flares, "sprites" which form things like
flames, clouds, etc).
  If people would never need a max_trace_level higher than about 300, then
they wouldn't have found this limit.

-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -

Post a reply to this message

>   Perhaps not 30000, but 300 and more could be necessary to render lots of
> semi-transparent objects (eg. lens flares, "sprites" which form things
like
> flames, clouds, etc).

Please write a (reasonable) POV-Ray scene where you can see the difference
between 50 and 80 levels.

(reasonable means : not a serie of 100 transparent planes)

Fabien.

Post a reply to this message

fabien <fab### [at] skynetbe> wrote:
: Please write a (reasonable) POV-Ray scene where you can see the difference
: between 50 and 80 levels.

  There is a visible difference between 50, 100 and 500 recursions in this
scene. Of course I could have came up with a scene where the difference is
more _important_, but I didn't have time for anything fancier.

global_settings { max_trace_level 500 }

camera { location <-1,2.5,-10> look_at y angle 35 }
light_source { <1000,2000,-1500>, 1 }
plane { y,0 pigment { rgb <1,.8,.4> } }

#declare GrassPatch =
  box
  { <-50,0,0><50,2,.1>
    pigment
    { spherical color_map
      { [0 rgbt <0,0,0,1>][.1 rgb y]
      }
      scale <.02, 1.95, .02>
      translate x*.1
      warp { repeat x*.2 }
      warp { turbulence x*.1 }
    }
  }

#declare S = seed(0);
#declare Ind = 0;
#while(Ind < 1000)
  object { GrassPatch translate <-2+4*rand(S),0,-5+Ind> }
  #declare Ind = Ind + 1;
#end


-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -

Post a reply to this message