Hi!

Is there a way to assign a (photon) TARGET keyword to a certain 
material? I'd like to make everything that is made of glass a photon 
target and now I have to specify TARGET individually to every glass 
object. If it is not possible, it would certainly be a most welcome 
feature - if feature wishes for the next relase can be made :-)

Severi S.

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sev### [at] NOT_THISsibafi news:402818a4$1@news.povray.org

> Is there a way to assign a (photon) TARGET keyword to a certain 
> material? I'd like to make everything that is made of glass a photon 
> target and now I have to specify TARGET individually to every glass 
> object. If it is not possible, it would certainly be a most welcome 
> feature - if feature wishes for the next relase can be made :-)

Maybe use macro instead

#macro matGlass()
  material { _matGlass }
  photons { ... }
#end

object { xxx matGlass() }


-- 
#macro g(U,V)(.4*abs(sin(9*sqrt(pow(x-U,2)+pow(y-V,2))))*pow(1-min(1,(sqrt(
pow(x-U,2)+pow(y-V,2))*.3)),2)+.9)#end#macro p(c)#if(c>1)#local l=mod(c,100
);g(2*div(l,10)-8,2*mod(l,10)-8)*p(div(c,100))#else 1#end#end light_source{
y 2}sphere{z*20 9pigment{function{p(26252423)*p(36455644)*p(66656463)}}}//M

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Rafal 'Raf256' Maj <spa### [at] raf256com> wrote:
> #macro matGlass()
>   material { _matGlass }
>   photons { ... }
> #end

> object { xxx matGlass() }

  That's a good idea, but I wonder if the 'photons' block should
be a part of the 'material' block...

  How would this look like?

material
{ texture { ... }
  interior { ... }
  photons { ... }
}

  OTOH this would introduce the problem of a material which always is
a target for photons even when you don't want to. There should perhaps
be a way of turning it off for specific objects...

-- 
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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Rafal 'Raf256' Maj wrote:

>>Is there a way to assign a (photon) TARGET keyword to a certain 
>>material? I'd like to make everything that is made of glass a photon 
>>target and now I have to specify TARGET individually to every glass 
>>object. If it is not possible, it would certainly be a most welcome 
>>feature - if feature wishes for the next relase can be made :-)
> 
> 
> Maybe use macro instead
> 
> #macro matGlass()
>   material { _matGlass }
>   photons { ... }
> #end
> 
> object { xxx matGlass() }

That is indeed a good suggestion, but it is hard to implement if you 
want to change an allready existing material - lots of parentheses to add...

Ok, you can use the Replace tool in your favourite text editor, but 
still... Adding photons to material description would be the easiest and 
the most intuitive way.

Severi

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Warp wrote:

> That's a good idea, but I wonder if the 'photons' block should
> be a part of the 'material' block...
> 
>   How would this look like?
> 
> material
> { texture { ... }
>   interior { ... }
>   photons { ... }
> }
> 
>   OTOH this would introduce the problem of a material which always is
> a target for photons even when you don't want to. There should perhaps
> be a way of turning it off for specific objects...

An overriding "target off" keyword would solve that.

Severi

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Warp wrote:
> 
>   That's a good idea, but I wonder if the 'photons' block should
> be a part of the 'material' block...
> 
>   How would this look like?
> 
> material
> { texture { ... }
>   interior { ... }
>   photons { ... }
> }

I don't think this would be a good idea, the way it is right now people 
recognize that photons are shot at objects and not at materials.  In 
fact photon shooting does not care about the material at all.

For example you could get the idea that assigning a material like:

material {
   texture {
     boxed
     texture_map {
       [0.5 Tex_Diffuse]
       [0.5 Tex_Reflective]
     }
   }
   photons { target reflection on }
}

to the whole scene could be reasonable.  This will lead to serious 
trouble though when your scene contains large or infinite objects.

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 11 Jan. 2004 _____./\/^>_*_<^\/\.______

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Christoph Hormann wrote:

> Warp wrote:
> 
>>
>>   That's a good idea, but I wonder if the 'photons' block should
>> be a part of the 'material' block...
 >
> I don't think this would be a good idea, the way it is right now people 
> recognize that photons are shot at objects and not at materials.  In 
> fact photon shooting does not care about the material at all.
> 
> For example you could get the idea that assigning a material like:
> 
> material {
>   texture {
>     boxed
>     texture_map {
>       [0.5 Tex_Diffuse]
>       [0.5 Tex_Reflective]
>     }
>   }
>   photons { target reflection on }
> }
> 
> to the whole scene could be reasonable.  This will lead to serious 
> trouble though when your scene contains large or infinite objects.

Of course, but I don't see the difference. You'll get equally big 
troubles if you assign target keyword straight to an infinite object or 
if you assign photon enabled material to the same object - no 
difference. I don't think making materials capable of being targets 
would make things any worse in that respect - you allways have to take 
care of what you are doing.

The point is just to make it easier to link certain things together with 
more freedom than now. Usually if someone has glass objects in a scene 
it is most likely he wants them all to show photon caustics. Material 
specific definition would be a nice way to do it. And, for example, if 
there was an infinite glass plane, specifying (say) "target off" would 
override the material photon definition.

Severi S.

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Severi Salminen wrote:
> [...]
> 
> Of course, but I don't see the difference. You'll get equally big 
> troubles if you assign target keyword straight to an infinite object or 
> if you assign photon enabled material to the same object - no 
> difference. I don't think making materials capable of being targets 
> would make things any worse in that respect

But materials can't be targets, only objects can.  The only way you can 
implement this is to make every object somehow 'inherit' the photon 
settings of its material.  But this would not be obvious to the user so 
it will just cause confusion in most cases.

> The point is just to make it easier to link certain things together with 
> more freedom than now. Usually if someone has glass objects in a scene 
> it is most likely he wants them all to show photon caustics. 

Most likely not.  For efficiency you will only use photons on those 
objects where the caustics are visible in the scene.  Glass objects out 
of direct view that are only visible as reflections in other shapes for 
example will probably not use photons.

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 11 Jan. 2004 _____./\/^>_*_<^\/\.______

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Christoph Hormann wrote:

> Severi Salminen wrote:
> 
>> [...]
> But materials can't be targets, only objects can.  The only way you can 
> implement this is to make every object somehow 'inherit' the photon 
> settings of its material.  But this would not be obvious to the user so 
> it will just cause confusion in most cases.

Materials can't be targets, true, but materials are allways assigned to 
certain objects, so yes, objects should inherit the photon settings. I 
thought this is obvious as there simply can't be an occurence of 
material without an object it is assigned to. And the whole point was to 
let material specify if an object needs photons. That is logical - same 
way as you might assign CAUSTICS keyword to certain material.

>> The point is just to make it easier to link certain things together 
>> with more freedom than now. Usually if someone has glass objects in a 
>> scene it is most likely he wants them all to show photon caustics. 
> 
> Most likely not.  For efficiency you will only use photons on those 
> objects where the caustics are visible in the scene.  Glass objects out 
> of direct view that are only visible as reflections in other shapes for 
> example will probably not use photons.

Why not? If the object itself is visible via reflection, then the 
caustics might also be. And if the object is not visible at all, then, 
why it exists at all? And actually this doesn't even matter: there are 
scenes that would benefit from material specific photons and there are 
scenes that would not. I don't see why implementing it would make things 
worse as you don't _have to_ use it allways - except that it needs to be 
implemented ;) It would simply make POV-SDL more versatile. But maybe 
POV-SDL will someday evolve to a form where this can be done easily.

PS. When the computers get faster, the caustics keyword will definitely 
be replaced by photon mapping (or some other technique) and it can be 
used in all objects. "Efficiency" is a very subjective word...

SeveriS

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SNIP
> I don't see why implementing it would make things
> worse as you don't _have to_ use it allways - except that it needs to be
> implemented ;) It would simply make POV-SDL more versatile. But maybe
> POV-SDL will someday evolve to a form where this can be done easily.
SNIP

Just to comment on this lone part of the discussion: I don't think that
making assumptions for the User is versatile. It often leads to places where
the User has to guess/assume what the Programm is assuming and
counter-effect that. POV-Ray, to me, was always about scripting what you
need and want. If I want a special effect, like photons, I have to put it
there, especially since photons can cause a load of data which would slow
down rendering even if not in sight. I was always glad that POV-Ray "ships"
with the most basic default settings, and assumes nothing, so that I know
*exactly* what's happening, when I view the code.

Oh, and "efficiency" has nothing to do with speed of PC's. If you don't need
calculations for effect, don't do them. That's efficiency: save where
possible.

Regards,
Tim

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>
Email: tim.nikias (@) nolights.de

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Tim Nikias v2.0 wrote:

> SNIP
> 
>>I don't see why implementing it would make things
>>worse as you don't _have to_ use it allways - except that it needs to be
>>implemented ;) It would simply make POV-SDL more versatile. But maybe
>>POV-SDL will someday evolve to a form where this can be done easily.
> 
> SNIP
> 
> Just to comment on this lone part of the discussion: I don't think that
> making assumptions for the User is versatile. It often leads to places where
> the User has to guess/assume what the Programm is assuming and
> counter-effect that. POV-Ray, to me, was always about scripting what you
> need and want. If I want a special effect, like photons, I have to put it
> there, especially since photons can cause a load of data which would slow
> down rendering even if not in sight. I was always glad that POV-Ray "ships"
> with the most basic default settings, and assumes nothing, so that I know
> *exactly* what's happening, when I view the code.

You are totally correct and I agree that the user should allways have 
the control. BUT:

Basically photon mapping is an effect in the same way as caustics, 
specular reflection, reflection etc. It uses different method and might 
cause considerable slowdown even when not visible, but it is still an 
effect and it can replace caustics, for example. And if caustics can be 
included in material definition, then why not photons as well? I simply 
don't understand why photons should be treated differently than the rest 
of the "effects".

And: if you assign photons to a material, why wouldn't you know what is 
happening? Why would you need to assume anything? If you assign that 
material to an object, that object will be used as photon target. Simple.

There are worse examples of guessing/assuming: using radiosity you are 
making every object emit light unless you alter the default ambient 
value. So not all default values are intuitive :)

> Oh, and "efficiency" has nothing to do with speed of PC's. If you don't need
> calculations for effect, don't do them. That's efficiency: save where
> possible.

Yes, but photons, for example might contribute to the visible part of 
the scene even when the object itself is not visible. So efficiency 
would be to test if the object affects to visible part and save the 
calculations if not. I have to admit I don't know exactly how photon 
mapping in POV-Ray works so it might be doing this kind of checking 
allready.

PS. I'm not trying to complain, I just proposed a feature that might be 
of some use to some people. To me, atleast ;-)

Severi S.

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>>
>> But materials can't be targets, only objects can.  The only way you 
>> can implement this is to make every object somehow 'inherit' the 
>> photon settings of its material.  But this would not be obvious to the 
>> user so it will just cause confusion in most cases.
> 
> 
> Materials can't be targets, true, but materials are allways assigned to 
> certain objects, so yes, objects should inherit the photon settings. I 
> thought this is obvious as there simply can't be an occurence of 
> material without an object it is assigned to. And the whole point was to 
> let material specify if an object needs photons. That is logical - same 
> way as you might assign CAUSTICS keyword to certain material.
> 
Just my thoughts on this. I think inheritance in this case is
a bad idea, especially if you combine it with 'target off'.
The properties of an object can then change with
the order in which the parts are added together.
Photons as a material property makes sense, but that would
probably mean a large rewrite of the code (if even possible).
Also it may break existing code.

    Andrel

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> Just my thoughts on this. I think inheritance in this case is
> a bad idea, especially if you combine it with 'target off'.
> The properties of an object can then change with
> the order in which the parts are added together.

I didn't quite follow you. Can you give an example?

> Photons as a material property makes sense, but that would
> probably mean a large rewrite of the code (if even possible).
> Also it may break existing code.

You can be 99.99% sure that it will never be implemented in present POV-Ray.
I believe it will be rewritten sooner or later anyway.

Severi

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Severi Salminen wrote:

>>Just my thoughts on this. I think inheritance in this case is
>>a bad idea, especially if you combine it with 'target off'.
>>The properties of an object can then change with
>>the order in which the parts are added together.
> 
> 
> I didn't quite follow you. Can you give an example?
Well, if you have an object which is partly glass
and partly some opaque material and you add 'target off'
to the latter part. Will the resulting object collect photons
(because of the glass part that switches it on, and
it is inherited by the total object) or not because
of the 'target of' in the other part. Will always the
first declaration take precedence or the last (or
even a middle one).

> 
>>Photons as a material property makes sense, but that would
>>probably mean a large rewrite of the code (if even possible).
>>Also it may break existing code.
> 
> 
> You can be 99.99% sure that it will never be implemented in present POV-Ray.
> I believe it will be rewritten sooner or later anyway.
> 
may I add 0.01% percent to that? Without looking into the
code I do not want to bet if it ever will. As I said, I
feel that a material property may make more sense but
it would require a exhaustive search through and deep into
all the  objects to see whether there is any photon active
material in it. If that is feasible depends on the
datastructures (I guess).

    Andrel

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In article <pgp### [at] tritonimagicode>,
 Christoph Hormann <chr### [at] gmxde> wrote:

> But materials can't be targets, only objects can.  The only way you can 
> implement this is to make every object somehow 'inherit' the photon 
> settings of its material.  But this would not be obvious to the user so 
> it will just cause confusion in most cases.

Why? It "inherits" the ior and media of its interior, the pigment of its 
texture, etc. There's nothing about photons that ties them specifically 
to the object, it doesn't own the photons. Making them an aspect of the 
material makes perfect sense to me. Glass objects have caustics...it's 
an aspect of glass, not of the objects.


> Most likely not.  For efficiency you will only use photons on those 
> objects where the caustics are visible in the scene.  Glass objects out 
> of direct view that are only visible as reflections in other shapes for 
> example will probably not use photons.

Even if they are out of direct view, their photons may be in view 
directly, or in reflections. And for the case where they really don't 
contribute, provide a mechanism for turning them off.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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In article <402### [at] hotmailcom>,
 andrel <a_l### [at] hotmailcom> wrote:

> > I didn't quite follow you. Can you give an example?
> Well, if you have an object which is partly glass
> and partly some opaque material and you add 'target off'
> to the latter part. Will the resulting object collect photons
> (because of the glass part that switches it on, and
> it is inherited by the total object) or not because
> of the 'target of' in the other part. Will always the
> first declaration take precedence or the last (or
> even a middle one).

The parts of the object that are glass will be photon targets. The parts 
with the opaque material will not. You can't apply multiple materials to 
a simple object, so there's no problem. (well, there may be a problem 
with difference and intersection, but no more than there is now)

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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In article <402### [at] hotmailcom>,
 andrel <a_l### [at] hotmailcom> wrote:

> Photons as a material property makes sense, but that would
> probably mean a large rewrite of the code (if even possible).

I highly doubt this. Actually, it would probably only require changes to 
parse.cpp...

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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Ok, I seem to have misunderstood you somewhere.
I thought that because the photons are an object
thing now, you wanted to promote the photon setting
from any material in an object to the object itself.

   Andrel

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"andrel" <a_l### [at] hotmailcom> kirjoitti viestissä
news:402### [at] hotmailcom...
> Ok, I seem to have misunderstood you somewhere.
> I thought that because the photons are an object
> thing now, you wanted to promote the photon setting
> from any material in an object to the object itself.

Oh, not at all. Sorry if I was unclear. If there was an object that is an
union of glass and wooden part, then the glass part should receive photons,
not everything. And if you, for any reason, don't want that glass part to
receive photons, then specify target off, or whatever. I just think it
should work just like caustics.

Post a reply to this message

Christopher James Huff wrote:
> 
> Why? It "inherits" the ior and media of its interior, the pigment of its 
> texture, etc. There's nothing about photons that ties them specifically 
> to the object, it doesn't own the photons. Making them an aspect of the 
> material makes perfect sense to me. Glass objects have caustics...it's 
> an aspect of glass, not of the objects.

I'd suggest you (and everyone else who thinks photons are just like 
(faked) caustics) to read up how they work before stating such 
conclusions.

The idea behind making photon settings part of the material certainly is 
to make it unnecessary for the user to think about which *objects* he 
wants how many photons for.  But since doing so will not actually change 
anything in the way POV-Ray distributes the photons this will not result 
in any actual improvement of the output quality or the render efficiency 
- it would just create the illusion for the user that he does not need 
to care about which objects should have photons.

What would really be interesting is a way for POV-Ray to automatically 
calculate the target values for the objects that receive photons based 
on their importance for the render result.  There have been various 
attempts for importance based photon distributions, a good introduction 
can (although focussed on global photons) be found in:

http://graphics.uni-ulm.de/Importance.pdf


Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 11 Jan. 2004 _____./\/^>_*_<^\/\.______

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> Oh, not at all. Sorry if I was unclear. If there was an object that is an
> union of glass and wooden part, then the glass part should receive photons,
> not everything. And if you, for any reason, don't want that glass part to
> receive photons, then specify target off, or whatever. I just think it
> should work just like caustics.
I think I understood what you wanted to achieve.
I had a problem with the way I thought it was supposed to
be realized. It is all clear to me now (I am a valid
target for photons again). Thanx,

    Andrel

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In article <vib### [at] tritonimagicode>,
 Christoph Hormann <chr### [at] gmxde> wrote:

> I'd suggest you (and everyone else who thinks photons are just like 
> (faked) caustics) to read up how they work before stating such 
> conclusions.

Completely irrelevant, and somewhat insulting. I understand how photons 
work. Yes, they are computed differently than faked caustics, that 
doesn't matter one bit. If transparency, reflection, and refraction are 
material attributes, it only makes sense for photons to be so as well.


> The idea behind making photon settings part of the material certainly is 
> to make it unnecessary for the user to think about which *objects* he 
> wants how many photons for.  But since doing so will not actually change 
> anything in the way POV-Ray distributes the photons this will not result 
> in any actual improvement of the output quality or the render efficiency 
> - it would just create the illusion for the user that he does not need 
> to care about which objects should have photons.

The point is to make it more convenient to write scenes. The fact that 
it won't improve efficiency or quality is entirely aside from the 
point...it isn't intended to do so in the first place.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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Christopher James Huff wrote:
> 
>>I'd suggest you (and everyone else who thinks photons are just like 
>>(faked) caustics) to read up how they work before stating such 
>>conclusions.
> 
> 
> Completely irrelevant, and somewhat insulting. I understand how photons 
> work. [...]

Since you wrote:

> There's nothing about photons that ties them specifically 
> to the object, it doesn't own the photons.

I had serious doubts about this...


Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 11 Jan. 2004 _____./\/^>_*_<^\/\.______

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In addition to what Christopher said...

Christoph Hormann wrote:
> I'd suggest you (and everyone else who thinks photons are just like 
> (faked) caustics) to read up how they work before stating such conclusions.

I think I know how photons work and yes, the aim is to produce (in case 
of refractive photons) more accurate caustics. I never claimed that 
"photons are just like (faked) caustics". But the goal is very similar 
in many cases.

> The idea behind making photon settings part of the material certainly is 
> to make it unnecessary for the user to think about which *objects* he 
> wants how many photons for.  But since doing so will not actually change 
> anything in the way POV-Ray distributes the photons this will not result 
> in any actual improvement of the output quality or the render efficiency 
> - it would just create the illusion for the user that he does not need 
> to care about which objects should have photons.

I'm starting to repeat myself, but here goes:

1. The suggestion was to make it easier to alter material 
characteristics. The _result_ of using photons is a material property: 
more realistic caustics and light reflections. Only the calculation 
method differs greatly from other properties and non-visible objects 
have an impact on total render time. I don't understand why this can be 
a reason to make the usage of photons more cumbersome than other 
material properties. Of course there should allways be ways to control 
the amount of time/memory consumed for this calculation.

2. The quality actually might improve as user might omit the usage of 
photons on an object that is not visible whereas reflected of refracted 
photons might still be visible in the field of view - even via 
reflections. The possibility of this happening might be reduced if 
photons were a material property. (And there is no point putting objects 
into scene which don't affect the output in any way...)

3. Why should POV-SDL have "baby-sitting" (no offense meant) features? I 
allways considered it to be quite powerful tool and it is up to user to 
understand what he is doing. It would have been equally odd, if (say, 10 
years ago) you would have been forced to specify refraction for each 
objects individually without having the possibility to inculde it to 
texture declaration: "They take very long to render and you must 
consider every object very carefully..." There are documents that 
explaine the usage of various features and I think users can judge 
themselves how to use them.

> What would really be interesting is a way for POV-Ray to automatically 
> calculate the target values for the objects that receive photons based 
> on their importance for the render result.  There have been various 
> attempts for importance based photon distributions, a good introduction 
> can (although focussed on global photons) be found in:

That would indeed be a good thing. Has any attempts made to implement 
such a thing in Pov-RAY?

Severi

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