Not only this is explains very clearly the problem, but it makes me think of a
relatively simple workaround when the cones are produced by a macro or a
utility : when the cone looks too much like a cylinder (rule to be defined,
problably a simple one), replace it by a cylinder !
Thanks Nathan.
Thanks also to Smellenbergh for providing the temporary code fix.
Unfortunately there's no way I can compile a patched version myself but it
will be helpful to other people.
Gilles

Nathan Kopp wrote:

> The big problem is that POV encloses the origin of the cone in the cone's
> bounding box.  The origin is the place where the cone narrows down to a
> single point.  So although your cone is only 30 units long or so, POV
> makes the bounding box big enough to fit a 1000 unit long cone (or some
> other really big number).
>
> -Nathan
>
> Gilles Tran wrote:
> >
> > This one puzzles me...
> > The code below shows 2 bunches of cones. One is called "slow", the other
> > one "quick". Render the code to see why : render the "quick" ones first
> > and then the "slow" ones.
> > The only difference between the slow and quick ones is that the slow
> > ones have a slightly larger base radius.
> > POV says that the slow cones are infinite objects !!!!
> > I came upon this problem when rendering a tree : for some mysterious
> > reason, some trees took forever to render (not counting parsing time).
> > The "slow" cones below were (painstakingly) extracted from a file
> > containing 16000 cones.
> >
> > Scaling the cones or moving the camera sometimes make the problem
> > disappear, sometimes not.
> >
> > Any idea about what's going wrong ?
> >
> > Gilles
> >
> > #include "colors.inc"
> > #declare PdV=<-1, 64 , -1>;
> > #declare PdA=<-1,64,0>;
> > camera {location  PdV direction <0.0 , 0.0 , 2 > up y  right 4*x/3
> > look_at   PdA}
> > //-----------------------------------------
> > light_source{<130,40,-200> color White*1.8}
> > #declare slow=
> > union{
> > cone{<-1.4877,62.1686,7.44824> ,0.204866,<-1.58298,62.4111,7.54819>
> > ,0.204862}
> > cone{<-1.58298,62.4111,7.54819> ,0.204862,<-1.67826,62.6535,7.64813>
> > ,0.204857}
> > cone{<-1.67826,62.6535,7.64813> ,0.204857,<-1.77355,62.896,7.74808>
> > ,0.204853}
> > cone{<-1.77355,62.896,7.74808> ,0.204853,<-1.86883,63.1384,7.84802>
> > ,0.204848}
> > cone{<-1.86883,63.1384,7.84802> ,0.204848,<-1.96411,63.3809,7.94797>
> > ,0.204844}
> > cone{<-1.96411,63.3809,7.94797> ,0.204844,<-2.05939,63.6233,8.04791>
> > ,0.20484}
> > cone{<-2.05939,63.6233,8.04791> ,0.20484,<-2.15468,63.8658,8.14786>
> > ,0.204835}
> > cone{<-2.15468,63.8658,8.14786> ,0.204835,<-2.24996,64.1082,8.2478>
> > ,0.204831}
> > cone{<-2.24996,64.1082,8.2478> ,0.204831,<-2.34524,64.3507,8.34775>
> > ,0.204826}
> > cone{<-2.34524,64.3507,8.34775> ,0.204826,<-2.44052,64.5931,8.44769>
> > ,0.204822}
> > cone{<-2.44052,64.5931,8.44769> ,0.204822,<-2.5358,64.8356,8.54764>
> > ,0.204818}
> > cone{<-2.5358,64.8356,8.54764> ,0.204818,<-2.63109,65.078,8.64758>
> > ,0.204813}
> > cone{<-2.63109,65.078,8.64758> ,0.204813,<-2.72637,65.3205,8.74753>
> > ,0.204809}
> > cone{<-2.72637,65.3205,8.74753> ,0.204809,<-2.82165,65.5629,8.84747>
> > ,0.204804}
> > cone{<-2.82165,65.5629,8.84747> ,0.204804,<-2.91693,65.8054,8.94741>
> > ,0.2048}
> > }
> > #declare quick=
> > union{
> > cone{<-1.4877,62.1686,7.44824> ,0.254866,<-1.58298,62.4111,7.54819>
> > ,0.204862}
> > cone{<-1.58298,62.4111,7.54819> ,0.254862,<-1.67826,62.6535,7.64813>
> > ,0.204857}
> > cone{<-1.67826,62.6535,7.64813> ,0.254857,<-1.77355,62.896,7.74808>
> > ,0.204853}
> > cone{<-1.77355,62.896,7.74808> ,0.254853,<-1.86883,63.1384,7.84802>
> > ,0.204848}
> > cone{<-1.86883,63.1384,7.84802> ,0.254848,<-1.96411,63.3809,7.94797>
> > ,0.204844}
> > cone{<-1.96411,63.3809,7.94797> ,0.254844,<-2.05939,63.6233,8.04791>
> > ,0.20484}
> > cone{<-2.05939,63.6233,8.04791> ,0.25484,<-2.15468,63.8658,8.14786>
> > ,0.204835}
> > cone{<-2.15468,63.8658,8.14786> ,0.254835,<-2.24996,64.1082,8.2478>
> > ,0.204831}
> > cone{<-2.24996,64.1082,8.2478> ,0.254831,<-2.34524,64.3507,8.34775>
> > ,0.204826}
> > cone{<-2.34524,64.3507,8.34775> ,0.254826,<-2.44052,64.5931,8.44769>
> > ,0.204822}
> > cone{<-2.44052,64.5931,8.44769> ,0.254822,<-2.5358,64.8356,8.54764>
> > ,0.204818}
> > cone{<-2.5358,64.8356,8.54764> ,0.254818,<-2.63109,65.078,8.64758>
> > ,0.204813}
> > cone{<-2.63109,65.078,8.64758> ,0.254813,<-2.72637,65.3205,8.74753>
> > ,0.204809}
> > cone{<-2.72637,65.3205,8.74753> ,0.254809,<-2.82165,65.5629,8.84747>
> > ,0.204804}
> > cone{<-2.82165,65.5629,8.84747> ,0.254804,<-2.91693,65.8054,8.94741>
> > ,0.2048}
> > }
> > #declare toto=object{quick} // render this  first
> > //#declare toto=object{slow} // render this last
> >
> > #declare i=-2;#while (i<5) #declare j=0;#while (j<20)
> > object{toto translate <i,0,j> pigment{Red}}
> > #declare j=j+1;#end #declare i=i+1;#end
> > background{White}

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