I don't think that the no_image flag should prevent the trace() function
from detecting the object. And often it does not. But sometimes it does.
Either way, the current behavior is very inconsistent, and must be a
bug. The minimal scene below demonstrates the problem.


// single sphere with no_image is detected by trace
//#declare Object = sphere {1, 0.0 no_image}

// sphere with no_image inside union is not!
#declare Object = union {sphere {0, 0.5} sphere {0, 1.0 no_image}}

#declare N = <0,0,0>;
#declare P = trace(Object,5*y,-y,N);
#debug concat("\n\nP: <",vstr(3,P,",",4,2),">   N:
<",vstr(3,N,",",4,2),">\n\n")


Tested using POV-Ray version 3.5.icl.win32

Rune
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In article <3f619f55$1@news.povray.org> , "Rune" <run### [at] runevisioncom>
wrote:

> I don't think that the no_image flag should prevent the trace() function
> from detecting the object. And often it does not. But sometimes it does.
> Either way, the current behavior is very inconsistent, and must be a
> bug. The minimal scene below demonstrates the problem.

It does detect the object.  The first object, and that is what it returns.
However, there can of course be more objects in its path...

    Thorsten

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

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On Fri, 12 Sep 2003 12:39:43 +0200, "Thorsten Froehlich" <tho### [at] trfde>
wrote:
> It does detect the object.  The first object, and that is what it returns.
> However, there can of course be more objects in its path...

IIRC trace() given by SDL checks only one object taken from its parameters.

ABX

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Thorsten Froehlich wrote:
> It does detect the object.  The first object,
> and that is what it returns. However, there
> can of course be more objects in its path...

I don't know what you mean by the "first" object.

There is an inner sphere and an outer sphere (with bigger radius). The
trace coming from outside point towards their centers should first hit
the sphere with the biggest radius. But when this sphere has no_image
specified, it is being ignored.

If, by "first" you refer to the order that the object are written down
in SDL, then I can inform that switching the order that the objects are
written down in SDL changes nothing. It is still the object without the
no_image keyword that is being returned.

In generel, I find your answer confusing. Are you confirming or denying
the bug?

Rune
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3D images and anims, include files, tutorials and more:
rune|vision:  http://runevision.com **updated Jul 25**
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In article <od93mvc7sdv0fhrrf0u8c691b77tvod0kk@4ax.com>,
 ABX <abx### [at] abxartpl> wrote:

> On Fri, 12 Sep 2003 12:39:43 +0200, "Thorsten Froehlich" <tho### [at] trfde>
> wrote:
> > It does detect the object.  The first object, and that is what it returns.
> > However, there can of course be more objects in its path...
> 
> IIRC trace() given by SDL checks only one object taken from its parameters.

But in this case, that one object is a union. I haven't looked at this 
very closely, but it looks like this may be an actual problem. The 
no_image flag should make no difference for trace().

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Could someone please post a formal bug confirmation as a reply here - or
else could someone make clear that it is not a bug?

Rune
--
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rune|vision:  http://runevision.com **updated Jul 25**
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So, I've tested your scene: once how you pasted
it here, and once with commenting the first, pure
no_image sphere in (and the latter one, with the
"normal" sphere inside, was commented out, of
course).

On both cases, it doesn't detect the no_image object,
but only the inner sphere with .5 radius.

I've got the official POV-Ray 3.5, Windows 2000,
768 MB DDR-RAM on AthlonXP 2400+.

Aside of that though:
IF the trace is based on the tracing rays of the
viewing screen, then I'd GUESS that it actually never
would  hit a no_image object anyway. Much like
radiosity doesn't see no_image objects. But
thats just a WILD GUESS which any newbie without
background knowledge should NOT listen to.

Rune, can you post a small example where it does
hit a no_image object?

-- 
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Email: no_lights (@) digitaltwilight.de


> Could someone please post a formal bug confirmation as a reply here - or
> else could someone make clear that it is not a bug?
>
> Rune
> --
> 3D images and anims, include files, tutorials and more:
> rune|vision:  http://runevision.com **updated Jul 25**
> POV-Ray Ring: http://webring.povray.co.uk
>
>


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Wasn't it Tim Nikias v2.0 who wrote:
>
>Rune, can you post a small example where it does
>hit a no_image object?
>
He almost did in his original post, except that there was a tiny typo.
The sphere should have been {0,1 no_image} rather than {1,0 no_image}

// single sphere with no_image is detected by trace
#declare Object = sphere {0,1 no_image}

// sphere with no_image inside union is not!
//#declare Object = union {sphere {0, 0.5} sphere {0, 1.0 no_image}}

#declare N = <0,0,0>;
#declare P = trace(Object,5*y,-y,N);
#debug concat("\n\nP: <",vstr(3,P,",",4,2),">   N:
<",vstr(3,N,",",4,2),">\n\n")

-- 
Mike Williams
Gentleman of Leisure

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Ah, okay. Didn't look out for that. So then, I can
confirm that the pure no_image works with
trace, but inside the given union (even if order
of objects are switched) it doesn't work.

POV-Ray for Windows, Win2000, AthlonXP 2.400+,
768 MB RAM

Regards,
Tim

-- 
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Email: no_lights (@) digitaltwilight.de


> Wasn't it Tim Nikias v2.0 who wrote:
> >
> >Rune, can you post a small example where it does
> >hit a no_image object?
> >
> He almost did in his original post, except that there was a tiny typo.
> The sphere should have been {0,1 no_image} rather than {1,0 no_image}
>
> // single sphere with no_image is detected by trace
> #declare Object = sphere {0,1 no_image}
>
> // sphere with no_image inside union is not!
> //#declare Object = union {sphere {0, 0.5} sphere {0, 1.0 no_image}}
>
> #declare N = <0,0,0>;
> #declare P = trace(Object,5*y,-y,N);
> #debug concat("\n\nP: <",vstr(3,P,",",4,2),">   N:
> <",vstr(3,N,",",4,2),">\n\n")
>
> -- 
> Mike Williams
> Gentleman of Leisure


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Tim Nikias v2.0 wrote:
> Ah, okay. Didn't look out for that. So then, I can
> confirm that the pure no_image works with
> trace, but inside the given union (even if order
> of objects are switched) it doesn't work.
>
> POV-Ray for Windows, Win2000, AthlonXP 2.400+,
> 768 MB RAM

Thanks to you both.

Rune
--
3D images and anims, include files, tutorials and more:
rune|vision:  http://runevision.com **updated Jul 25**
POV-Ray Ring: http://webring.povray.co.uk

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