Just a thought:
If dust from this discussion is settled down and common ground is found,
then perhaps someone could summarize it and put it available (e.g. as
guideline for rule-of-thumb)?

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Vahur Krouverk wrote:
> 
> Just a thought:
> If dust from this discussion is settled down and common ground is found,
> then perhaps someone could summarize it and put it available (e.g. as
> guideline for rule-of-thumb)?

You will probably find that on this topic that one mans rule of thumb
is another mans big toe.

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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On Thu, 11 Jan 2001 08:45:50 -0800, Ken wrote:
>
>
>Vahur Krouverk wrote:
>> 
>> Just a thought:
>> If dust from this discussion is settled down and common ground is found,
>> then perhaps someone could summarize it and put it available (e.g. as
>> guideline for rule-of-thumb)?
>
>You will probably find that on this topic that one mans rule of thumb
>is another mans big toe.

What he said.

The only general rule of thumb is "tweak it til it looks right in your scene."

-- 
Ron Parker   http://www2.fwi.com/~parkerr/traces.html
My opinions.  Mine.  Not anyone else's.

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"Vahur Krouverk" <vah### [at] aetecee> wrote in message
news:3A5DE21E.13B70413@aetec.ee...
> Just a thought:
> If dust from this discussion is settled down and common ground is found,
> then perhaps someone could summarize it and put it available (e.g. as
> guideline for rule-of-thumb)?

1. A scene with white walls needs higher ambient than a scene with black
walls.

2. Ambient and diffuse have a relationship to each other and an inverse
relationship to reflection.

3. Don't use ambient, use radiosity. With media. And isosurfaces. On a 386.

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Tom Melly wrote:
> 1. A scene with white walls needs higher ambient than a scene with black
> walls.
> 
> 2. Ambient and diffuse have a relationship to each other and an inverse
> relationship to reflection.
> 
> 3. Don't use ambient, use radiosity. With media. And isosurfaces. On a 386.
Guess I should downgrade my 486 in this case...

Arghh, I'm off to read "Digital Lighting & Rendering"

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In article <3A5DE21E.13B70413@aetec.ee>, Vahur Krouverk 
<vah### [at] aetecee> wrote:

> Just a thought:
> If dust from this discussion is settled down and common ground is found,
> then perhaps someone could summarize it and put it available (e.g. as
> guideline for rule-of-thumb)?

As mentioned, pretty much everyone has their own "rule of thumb", and 
you will have to just develop your own. However, this is how I do 
things, but note that much of this applies to MegaPOV only:

Make sure ambient+diffuse+reflection <= 1
(I don't include specular in this, because it only applies to certain 
angles relative to each light_source...just adjust it until you get the 
highlights you want. I never use phong highlights. If you use 
iridescence, that should probably go into the above calculations.)

metallic on
reflect_metallic on
conserve_energy on
Use Fresnel reflection function if applicable (a surprisingly large 
number of situations).

I get best results with ambient 0 and radiosity. A high ambient robs the 
scene of contrast and depth, so the only times I use an ambient other 
than 0 is when I have a glowing object or have an object that just needs 
to show up (I sometimes use ambient 1 cylinders aligned along each axis 
for orientation). For test renders, I usually don't use radiosity, but I 
put a light_source at the position of the camera. This helps illuminate 
dark shadows but doesn't destroy the depth cues like ambient does.

Also, I always use "filter", never "transmit" for transparence. When I'm 
going for a realistic transparent material, I use a filter value of 1 
and use absorbing media or fade_color (using the "realistic attenuation" 
function) to tint the glass to the right color. This makes thick areas 
dark and very thin areas almost invisible, which is how things work in 
reality.
Dispersion can add a very nice touch, and photons can really add to your 
scene if you have reflective/refracting objects and something they can 
cast light on (mainly dull surfaces or media, anything you would notice 
light caustics on normally).

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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On Thu, 11 Jan 2001 16:42:22 -0500, Chris Huff wrote:
>Also, I always use "filter", never "transmit" for transparence. When I'm 
>going for a realistic transparent material, I use a filter value of 1 
>and use absorbing media or fade_color (using the "realistic attenuation" 
>function) to tint the glass to the right color. This makes thick areas 
>dark and very thin areas almost invisible, which is how things work in 
>reality.

Transmit has a different purpose.  Transmit is supposed to be used for
things like gauze or nylon fabric or tracing paper or other things that 
are transparent because they have a bunch of tiny subpixel holes in them 
rather than because they are made of a semitransparent material.

-- 
Ron Parker   http://www2.fwi.com/~parkerr/traces.html
My opinions.  Mine.  Not anyone else's.

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In article <slr### [at] fwicom>, ron### [at] povrayorg 
wrote:

> Transmit has a different purpose.  Transmit is supposed to be used for
> things like gauze or nylon fabric or tracing paper or other things that 
> are transparent because they have a bunch of tiny subpixel holes in them 
> rather than because they are made of a semitransparent material.

True...there are exceptions to that rule. None of them are completely 
rigid...but that would be a good addition to that rule, and I will keep 
it in mind from now on.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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Ron Parker wrote:

> Ambient is equivalent to "diffuse reflection from unknown light sources" and
> as such should probably also be included in the sum.  I always include it in
> the sum, at any rate.

That is what I find odd in the lighting model as there is also an
"ambient_light" global setting. Ambient background light is still diffusely
reflected light, versus an object's own ambience.

--
David Fontaine  <dav### [at] faricynet>  ICQ 55354965
My raytracing gallery:  http://davidf.faricy.net/

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Tom Melly wrote:
> 
> "Francois Labreque" <fla### [at] videotronca> wrote in message
> news:3A5DCD94.E1942106@videotron.ca...
> >
> > I personally prefer setting ambient to 0 and let radiosity take care of
> > all this stuff.  But then again, I have the horsepower necessary for it,
> > so ymmv.
> >
> 
> I personally prefer it if people don't rub my nose in the fact that a P90 is
> not the ideal rendering platform - particularily if they're french ;)

Does it help my case if I told you that we share the same Queen?

-- 
Francois Labreque | Unfortunately, there's no such thing as a snooze
    flabreque     | button on a cat who wants breakfast.
        @         |      - Unattributed quote from rec.humor.funny
   videotron.ca

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