I'd like to know if some of you have some tips to render metallic
textures.
What kind of value they give to brilliance, diffuse, ambient,.....
If they add normal to it.....

I'd like to know how the others deal with it and how they build them.

Thanks

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news:3968E842.8F9AD9E6@club-internet.fr...
| I'd like to know if some of you have some tips to render metallic
| textures.
| What kind of value they give to brilliance, diffuse, ambient,.....
| If they add normal to it.....
|
| I'd like to know how the others deal with it and how they build them.

Asking the wrong person here, I use such a variety of values in each of those
keywords.  Don't forget specular highlights and reflection too.  Really
depends on the type metal you are trying to make.  metals.inc file shows the
usual way to go about it.  Sometimes you might also want some 'crand' in
there.  I think one of the more important aspects of a metal is the amount of
reflection color plus diffuse.  'reflection_blur' and 'reflect_metallic' in
MegaPov are a couple other things.
Anyway, it gets to be difficult to narrow it all down; a glass object can look
very much the same as a metal one if both are very reflective and chrome-like.
A dirty rusted metal can seem similar to stone.

Bob

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<ffj### [at] club-internetfr> wrote:

>I'd like to know if some of you have some tips to render metallic
>textures.
>What kind of value they give to brilliance, diffuse, ambient,.....
>If they add normal to it.....
>
>I'd like to know how the others deal with it and how they build them.

I am not an expert in any case but anyway see if my experience is of
help.

Pigment:

A solid color :) I prefer unsaturated colors for metals but of course
there are exceptions, such as copper or gold.

Finish:

I always go for a low ambient (0.05-0.2) and a diiffuse equal to
1-ambient (unless reflection is used), using a brilliance from 1.75 to
3.25, usually setting in the range 2.25-2.75. I also always use two
highlights, a tight specular in the range 0.5-1 and roughness
0.0005-0.005 and a soft phong with half the specular's intensity and a
phong_size in the range 20-5. With these, I use metallic 0.75-1,
usually 0.9 or so. Reflection is also important, but I never go over
0.5. With MegaPOV, reflect_metallic is also very helpful, as much as
metallic itself.

Normal:

I don't usually use a normal unless I want to achieve some kind of
anisotropy. In this case I use a very finely scaled normal (like scale
0.0001 - 0.001 for a unit sphere) following the direction of the
anisotropy. For example, if a brushed aluminum Utah teapot is what
you're after, you can give the lid a wood normal with a very high
frequency (1000-10000) or scaled very small. As a rule og thumb that I
use, there should be two or more complete waveforms of the normal in
every pixel. This, of course, requires antialiasing settins akin to
+am0.025 +am2 +r3 +j1.0 +patience=Godlike , but it is (still) the only
way to achieve anisotropy in POV.

Photons:

Photons help if the object is a) reflective and b) complex. It has to
have some way to reflect light onto itself and then photons make
wonders for photorealism.

Radiosity:

I've hardly used radiosity so I can't help you any here, sorry.

Maybe you'll find some of the above applicable.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG      e-mail : pet### [at] tagpovrayorg

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> <ffj### [at] club-internetfr> wrote:
>
> >I'd like to know if some of you have some tips to render metallic
> >textures.
> >What kind of value they give to brilliance, diffuse, ambient,.....
> >If they add normal to it.....
> >
> >I'd like to know how the others deal with it and how they build them.
>
> I am not an expert in any case but anyway see if my experience is of
> help.
>
> Pigment:
>
> A solid color :) I prefer unsaturated colors for metals but of course
> there are exceptions, such as copper or gold.
>

By unsaturated, do you mean a color like <0.2,0.2,0.2> ?

>
> Finish:
>
> I always go for a low ambient (0.05-0.2) and a diiffuse equal to
> 1-ambient (unless reflection is used), using a brilliance from 1.75 to
> 3.25, usually setting in the range 2.25-2.75.

> I also always use two
> highlights, a tight specular in the range 0.5-1 and roughness
> 0.0005-0.005 and a soft phong with half the specular's intensity and a
> phong_size in the range 20-5.

Ah maybe that's the trick I was looking for : A soft and a tight
highlights.

> With these, I use metallic 0.75-1,
> usually 0.9 or so. Reflection is also important, but I never go over
> 0.5. With MegaPOV, reflect_metallic is also very helpful, as much as
> metallic itself.

Reflect_metallic ? I am going to browse the MegaPOV help more thoroughly.
Apparently, I have missed a few interesting new features

>
> Normal:
>
> I don't usually use a normal unless I want to achieve some kind of
> anisotropy. In this case I use a very finely scaled normal (like scale
> 0.0001 - 0.001 for a unit sphere) following the direction of the
> anisotropy. For example, if a brushed aluminum Utah teapot is what
> you're after, you can give the lid a wood normal with a very high
> frequency (1000-10000) or scaled very small. As a rule og thumb that I
> use, there should be two or more complete waveforms of the normal in
> every pixel. This, of course, requires antialiasing settins akin to
> +am0.025 +am2 +r3 +j1.0 +patience=Godlike , but it is (still) the only
> way to achieve anisotropy in POV.
>
> Photons:
>
> Photons help if the object is a) reflective and b) complex. It has to
> have some way to reflect light onto itself and then photons make
> wonders for photorealism.
>
> Radiosity:
>
> I've hardly used radiosity so I can't help you any here, sorry.
>
>

Thanks for all



> Maybe you'll find some of the above applicable.
>
> Peter Popov ICQ : 15002700
> Personal e-mail : pet### [at] usanet
> TAG      e-mail : pet### [at] tagpovrayorg

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news:396A1229.DB10069A@club-internet.fr...
|
| By unsaturated, do you mean a color like <0.2,0.2,0.2> ?

You need to keep in mind that the objects color will contribute to the
reflected colors; so for iron this darker color might be suitable, but not for
steel or any metal which appears to lighten the things reflected in it.

Bob

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<ffj### [at] club-internetfr> wrote:

>By unsaturated, do you mean a color like <0.2,0.2,0.2> ?

Yes. If you grab the HSB <--> RGB macros (search the scene-files
groups) you'll make your life easier. Start with saturation 0 and
brightness 100 (hue doesn't play a role yet) and start reducing
brightness until you're down to what you want it to be.. Then reduce
saturation until you have to the color as juicy as you want it, and at
the same time adjust the hue. Tweak the brightness for the last time
because the way it is perceived may have changed with the addition of
color.

>Ah maybe that's the trick I was looking for : A soft and a tight
>highlights.

The tight highlight looks like a bulb and the soft one looks like
radiosity from the ceiling near the bulb. Or they may look like the
sun and the window. Definitely looks better with two.

>Reflect_metallic ? I am going to browse the MegaPOV help more thoroughly.
>Apparently, I have missed a few interesting new features

Well, there's blurred reflection in there, too, but I don't see where
you'll use it. There's also variable reflection and energy
conservation but I don't think variable reflection is applicable for
metals to a degree as to be noticeable (like water or linoleum).


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG      e-mail : pet### [at] tagpovrayorg

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