Hi,




take. Is there somebody have an idea?

Thank you

Sylvain

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> Hi,




> take. Is there somebody have an idea?
> 
> Thank you
> 
> Sylvain
> 
> 
> 
No. Photons are cast after the parsing is done so they cannot influence 
the parsing. The only possible way would be to parse the photons file 
using an external application. I don't understand its structure, though.

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web.47d7e7fcede45537dcf53ead0@news.povray.org...
> Hi,
> I'm using POV-Ray to simulate a laser beam pointed to a screen. I'm also 
> using
> photons in my programming and I would like to know if it's possible to 
> detect
> photons on my screen. Does there exist any function for this? I'm looking 
> for a

> approach
> take. Is there somebody have an idea?
>
> Thank you
>
> Sylvain


trace() is the best way to test if a ray hits an object and to know the 
coordinates and normal of the intersection point.


Marc

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M_a_r_c napsal(a):

> web.47d7e7fcede45537dcf53ead0@news.povray.org...
>> Hi,
>> I'm using POV-Ray to simulate a laser beam pointed to a screen. I'm also 
>> using
>> photons in my programming and I would like to know if it's possible to 
>> detect
>> photons on my screen. Does there exist any function for this? I'm looking 
>> for a

>> approach
>> take. Is there somebody have an idea?
>>
>> Thank you
>>
>> Sylvain
> 
> 
> trace() is the best way to test if a ray hits an object and to know the 
> coordinates and normal of the intersection point.
> 
> 
> Marc 
> 
> 
I think he needs to trace the beam through a series of mirrors and 
lenses. This is quite difficult in SDL at the very least.

-- 
the ultimate time-killer:
+a0.0 +am2 +r9

Johnny D

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Sylvain Dubé nous apporta ses lumieres en ce 2008/03/12 10:26:
> Hi,
> I’m using POV-Ray to simulate a laser beam pointed to a screen. I’m also using
> photons in my programming and I would like to know if it’s possible to detect
> photons on my screen. Does there exist any function for this? I’m looking for a
> command like « trace » to know where are my impact. I cannot know which approach
> take. Is there somebody have an idea?
> 
> Thank you
> 
> Sylvain
> 
> 
> 
The trace function return the intersection point between a line shoot from an 
arbitrary point toward a previously deffined object. It only return the first 
intersection point and, optionaly, the normal at the found point. It ignore any 
reflectivity. It also ignore any transparency.
It ignore any object exept it's target object.

As the sequance of events of a render is: parse, [shoot photons], [do radiosity 
pretrace], render. The "[...]" denote optional steps. You can't access the 
photons white parsing, even if you use the load file option for your photons. 
The photons data from the file are loaded after the parsing is finished.

If your laser never reflect or refract before it reatch the screen, you don't 
need photons at all. Just use a light_source with the parallel and cylindrical 
atributes.


If you want to see where the photons go, you need some surface to catch them. 
The screen you mention is perfect for that task. Just make it white. You don't 
need to add a photons block to it's definition, it default to collect ON.
If you want to see their trajectory, you need to fill the scene with scattering 
media.

-- 
Alain
-------------------------------------------------
Hinduism: This shit has happened before.

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Wasn't it Alain who wrote:
>Sylvain Dubé nous apporta ses lumieres en ce 2008/03/12 10:26:
>> Hi,
>> I’m using POV-Ray to simulate a laser beam pointed to a screen. 
>>I’m also using
>> photons in my programming and I would like to know if it’s possible 
>>to detect
>> photons on my screen. Does there exist any function for this? I’m 
>>looking for a
>> command like ? trace ? to know where are my impact. I cannot know 
>>which approach
>> take. Is there somebody have an idea?
>>  Thank you
>>  Sylvain
>>
>The trace function return the intersection point between a line shoot 
>from an arbitrary point toward a previously deffined object. It only 
>return the first intersection point and, optionaly, the normal at the 
>found point. It ignore any reflectivity. It also ignore any transparency.
>It ignore any object exept it's target object.

If you know the reflection, transparency and IOR of the object you've 
hit, you can use that information to trace() new reflected and refracted 
photon paths onwards from that intersection point.

You don't know which object those reflected photons are going to hit 
next, so you have to use trace() against every candidate object and 
select the one that has the nearest intersection point.

-- 
Mike Williams
Gentleman of Leisure

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Is MegaPOV have any function for this?

Sylvain

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Sylvain Dubé nous apporta ses lumieres en ce 2008/03/14 14:52:
> Is MegaPOV have any function for this?
> 
> Sylvain
> 
> 
> 
Not that know of.

You should use user functions and macros to do the task.

Don't forget that when you enter an object, your next trace will be toward that 
same object to find the exit point. This can lead to multiple total internal 
reflections.

Once you exit an object, there are cases where that object can be a valid 
target. Any object with any concavity or opening can interact more than twice.

Any concave reflective object can reflect a ray more than once.

All this mean that you may need a recursive function.

-- 
Alain
-------------------------------------------------
   I'm so ugly I stuck my head out the window and got arrested for Mooning.
   	Rodney Dangerfield

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