"Warp" <war### [at] tagpovrayorg> wrote in message
news:3e8095f9@news.povray.org...

>   Uh? Calculating the intersection point of a ray and a surface which
> is very very far away does not take any longer than with a surface
> which is close. Why would you think it does?

Well, I was kind of thinking that an infinite plane would require an
infinite number of rays to trace since there would be an infinite number of
places that a ray could intersect (and that would be potentially in view).

However, on reflection, it occurs to me that:
a) the number of rays is limited by the resolution
and
b) that would just be silly.

Toodleoo.

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"Marc Jacquier" <jac### [at] wanadoofr> wrote in message
news:3e809ff1@news.povray.org...

> /*
>  * These values determine the minumum and maximum distances
>  * that qualify as ray-object intersections.
>  */

Many thanks.

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Tom & Lu Melly <all### [at] tomandlucouk> wrote:
> Well, I was kind of thinking that an infinite plane would require an
> infinite number of rays to trace since there would be an infinite number of
> places that a ray could intersect

  A ray can intersect a plane only in one place. There's no way for a ray
to intersect a plane in more than one place (unless it bends somehow). :)

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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Marc Jacquier <jac### [at] wanadoofr> wrote:
> #define Small_Tolerance 0.001
> #define Max_Distance 1.0e7

  IMHO those values should be promptly changed...

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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3e80c6c4@news.povray.org...
> Marc Jacquier <jac### [at] wanadoofr> wrote:
> > #define Small_Tolerance 0.001
> > #define Max_Distance 1.0e7
>
>   IMHO those values should be promptly changed...

I agree they are limitating when you need close-small and remote-huge
objects in the same scene

Marc

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Thanx, I think this will help me. 
Only - it is not GPL software and the source distributen is awful ;-)

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"Warp" <war### [at] tagpovrayorg> wrote in message news:3e80c672@news.povray.org...
>
>   A ray can intersect a plane only in one place. There's no way for a ray
> to intersect a plane in more than one place (unless it bends somehow). :)

Sorry, I'm not explaining my question/confusion well (which is now pretty much
resolved).

A plane stretching to infinity would, presumably, need an infinite bounding box
(otherwise it's not infinite). An infinite number of rays would be required to
trace it, since there would be an infinite number of intersection points. This
would take an infinite amount of time. This is obviously wrong, but I was
curious as to how it was wrong, which I think I now largely understand.

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Tom Melly <tom### [at] tomandlucouk> wrote:
> A plane stretching to infinity would, presumably, need an infinite bounding box
> (otherwise it's not infinite).

  I think an infinite object does not have a bounding box at all.

> An infinite number of rays would be required to
> trace it, since there would be an infinite number of intersection points.

  I don't understand how you came to this conclusion.
  An infinite number of intersection points to calculate what? For one
pixel we need one intersection point (unless using antialiasing, which
means we may need something like 9 intersection points). What do you need
to calculate an infinite amount of intersection points for?

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

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"Warp" <war### [at] tagpovrayorg> wrote in message news:3e8175ca@news.povray.org...
>
>   I don't understand how you came to this conclusion.

You obviously forgot to factor in my idiocy.

>   An infinite number of intersection points to calculate what? For one
> pixel we need one intersection point (unless using antialiasing, which
> means we may need something like 9 intersection points). What do you need
> to calculate an infinite amount of intersection points for?

This is the solution to my confusion (and fairly bleedin' obvious when I think
about it). I was thinking that the number of rays required to trace an object
was dependant on the object's actual size (infinite in the case of a plane),
whereas the number of rays is more dependant on the area of the image that the
object occupies (always finite).

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"Warp" <war### [at] tagpovrayorg> wrote:
>
>   I think an infinite object does not have a bounding box at all.
>
Internally, infinite objects are even kept in a separate list, at scene
root, outside of any hierarchies.

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