"Nathalie" <nomail@nomail> wrote:
> I would like to reformulate my question a bit. It is not my intention to make a
> perfect rendering of a church interior. It is rather my intention to render a
> part of a church interior (let's say a niche with a statue) according to three
> daylight calculation methods (ray-tracing, radiosity and photon mapping), with
> the aim of comparing these three methods. I tought POV-ray was the best choice
> to do this, because it makes control over the algorithms possible. Effects to
> improve the rendering (like glow,...) are only interesting insofar as they are
> applicable to the three calculation methods. Is this possible with POV-Ray?
> Because from the previous answers I deducted that only radiosity was possible...
> Please correct me if I'm wrong.
> best regards,
From the first postings here I had the impression that there is a little bit
misunderstanding between the entrants here. I hope I can clarify the one or
Nathalie, you have three items in your list: ray tracing, radiosity and photons.
Ray tracing: The idea is to trace a ray, but backwards. Imagine a usual camera.
It samples the rays that hit the lense and make a photograph of it. Ray tracing
is the other way round. You are looking from the film (or a sensor nowadays)
throught the lens into the world trying to find a way to a light. (That is why
"ray tracing" is sometimes more precisely called "backward ray tracing"). This
works fine, if you hit a light. And this is that what POV always does. So if you
are using POV you can rule out the first item of your list. POV is created to do
Radiosity: Often the ray from the camera cannot find a light at a direct course.
That is simply because you are in a shadow. The work around here is to snoop
around in some other directions to find a light from this point at an indirect
path. That is not trivial since you have to specify a lot of parameters how this
should be done, but fortunatelly there is the include-file "rad_defs.inc" with
provides a lot of parametrisations under names, one can understand.
"Radiosity_OudoorLQ" e.g., with gives a low quality (LQ) setting for outdoor
scenes. There is a HQ (high quality) setting as well, but first try the LQ since
the HQ renders much longer than the LQ. (LQ may cost some hours, HQ some days -
Photons: If you are looking backwards from the camera to the lights you cannot
see direct effects of the lights like reflections on a wall or reflected and
refracted light by a water glass. Photons are a precalculating step to work
aorund this. You need a lot of experience or a lot of experiments to achieve a
fine result (no include file can be created for this issue).
Ray tracing is the nature of POV, for radiosity I will propose you to work
through the tutorial which came with POV (within the help-files). A fine
reference picture for photons is an entry to the POVComp contest by Tilo Helmig
Source codes are included there.
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