Dear all,

I'm not sure whether I should have posted this question to the
povray.newusers.
Well, I am enjoying learning the Photon features.

First, I'd like to know whether the photon-map is reusable, even when I
changed the size of the rendered image, or the viewing conditions such as
camera (with fixed lighting and models).

I'd also like to learn where I could get instructions to saving and loading
photon maps.

Thanks in advance,

Jong

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"Jong" <jjk### [at] mmewhaackr> wrote in message
news:3bc51321@news.povray.org...
>
> I'm not sure whether I should have posted this question to the
> povray.newusers.

This is the right place for that question if you have MegaPOV, but if you
have the new P-R v3.5 beta you could have asked at either newusers or
general.

> First, I'd like to know whether the photon-map is reusable, even when I
> changed the size of the rendered image, or the viewing conditions such as
> camera (with fixed lighting and models).
>
> I'd also like to learn where I could get instructions to saving and
loading
> photon maps.

The map is really meant for ease in rerunning a unchanged scene again but
resolution should be okay.  Changing the field of view without moving the
camera might work out somewhat but I myself couldn't say for certain.  I've
reloaded maps before and made changes but never really kept tabs on how good
or bad a result that can be.

All that is required to use them is to put the keywords in, like so:

global_settings {
    photons {
        PHOTON ITEMS
        save_file "MyPhoton.phm"
    }
}

...or...

global_settings {
    photons {
        PHOTON ITEMS
        load_file "MyPhoton.phm"
    }
}

Using a #if() #end to discern which you want to do can help.

Bob H.

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> First, I'd like to know whether the photon-map is reusable, even when I
> changed the size of the rendered image, or the viewing conditions such as
> camera (with fixed lighting and models).

Changing the size of the image is no problem as the photon map is resolution
indenpendent.  Any lacking in the quality of the photons will become more
apparent in a larger image but it's the same quality as it would be in a
smaller one.  Changing the camera angle might cause problems though I'm not
sure.  Any other changes are not a problem but keep in mind that the
caustics will look the same even if you change object or light locations.
In other words the photons are fixed in space.  Moving an object hit by
photons might cause the surface to be outside the range of the photon map.
This seems to be the way it works based on my experience.  Radiosity files
can be saved and loaded just like photons maps btw.

> I'd also like to learn where I could get instructions to saving and
loading
> photon maps.

Very easy.  In the photon block in global settings, add a line:
save_file "filename.ph"

To reload the map change that to
load_file "filename.ph"

The file gets saved to the same location as the scene file.  You might be
able to put a path in there but I'm not 100% sure.  I recently used this
trick in an animation (trout.mpg in p.b.a) so that I could create a series
of photon maps with simple geometry and reloaded them for a more complex
scene, thus saving time.  Concat() can be used for this purpose, such as:
#declare CURRENT_FRAME = clock;
save_file concat("myfile",str(CURRENT_FRAME,0,0), ".ph" )

This requires clock to be an integer value.  I find thinking of the clock as
representing frames is easier than using floating point values.

Post a reply to this message

"Jong" <jjk### [at] mmewhaackr> wrote...
> First, I'd like to know whether the photon-map is reusable, even when I
> changed the size of the rendered image, or the viewing conditions such as
> camera (with fixed lighting and models).

You can most things.  Avoid changing these:
1) size/location of objects that interact with photons in any way (either
collect them or reflect/refract them)
2) size/brightness of lights that shoot photons
3) textures of objects that reflect or refract photons

Actually, you can change those, but the results will then be unrealistic.

-Nathan

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Dear Mike, Bob, and Nathan

Thank you all so much for your kind replies to my newbie question.

Jong
jjk### [at] mmewhaackr


"Nathan Kopp" <nat### [at] koppcom> wrote in message
news:3bc66275$1@news.povray.org...
>
> "Jong" <jjk### [at] mmewhaackr> wrote...
> > First, I'd like to know whether the photon-map is reusable, even when I
> > changed the size of the rendered image, or the viewing conditions such
as
> > camera (with fixed lighting and models).
>
> You can most things.  Avoid changing these:
> 1) size/location of objects that interact with photons in any way (either
> collect them or reflect/refract them)
> 2) size/brightness of lights that shoot photons
> 3) textures of objects that reflect or refract photons
>
> Actually, you can change those, but the results will then be unrealistic.
>
> -Nathan
>
>
>

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Nathan Kopp <nat### [at] koppcom> wrote:
: 2) size/brightness of lights that shoot photons

  You forgot to mention the color of the light source... :)

-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -

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