 |
|
|
|
|
|
| |
| |
|
|
|
|
| |
| |
|
|
clipka <ano### [at] anonymous org> wrote:
>
> Um... a looks_like object should _always_ have a emission! Otherwise it
> won't look like what a light source would look like.
>
>
> However, And has correctly hinted someplace else at conflict between
> different ways of simulating the same thing when using a "looks_like"
> object. A light source should only show up in one of the two ways of
> each of the following pairs:
>
> - Classic diffuse illumination vs. radiosity: A "looks_like" object
> should always have "no_radiosity on" set, which unfortunately isn't the
> default. (Theoretically, an alternative would be to make the light
> source invisible for the sake of the "diffuse" component, but in
> practice that doesn't make any sense due to the vast differences in
> computational effort; if you want to go that far, just leave out the
> light source entirely and go with the "looks_like" object alone.)
>
> - Specular highlights vs. reflections: A "looks_like" object should have
> "no_reflection on" set. An alternative would be to make the light source
> invisible for the sake of specular highlights, but POV-Ray doesn't
> support this at the moment (which puts me to shame, as I must admit).
Thanks for the interpretation.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Thomas de Groot <tho### [at] degrootorg> wrote:
> On 26-6-2015 8:58, Stephen wrote:
> > On 26/06/2015 07:34, And wrote:
> >> "And" <49341109@ntnu.edu.tw> wrote:
> >>
> >> I'm very smart.!!
> >>
> >
> > LOL
> > You are too. :-)
> >
>
> Why do I feel depressed now? :-)
>
> --
> Thomas
giggle.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
> - Always use "fresnel on" for reflections (don't forget to specify
> "ior"), or "metallic on" where applicable, and always use 0.0 for the
> minimum reflection (or leave it out, specifying the maximum reflection
> only).
If you are using fresnel, is it valid (from a PBR point of view) to even
scale the results using a maximum reflection other than 1?
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Am 02.07.2015 um 10:25 schrieb scott:
>> - Always use "fresnel on" for reflections (don't forget to specify
>> "ior"), or "metallic on" where applicable, and always use 0.0 for the
>> minimum reflection (or leave it out, specifying the maximum reflection
>> only).
>
> If you are using fresnel, is it valid (from a PBR point of view) to even
> scale the results using a maximum reflection other than 1?
Absolutely - if, for instance, your surface is littered with
non-specular material at a microscopic level. Fine rust on iron steel,
for instance, or a thin coating of dust.
In those cases it might be better, however, to use an average of two
materials.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On Thu, 02 Jul 2015 18:16:23 +0200, clipka <ano### [at] anonymousorg> wrote:
> Am 02.07.2015 um 10:25 schrieb scott:
>>> - Always use "fresnel on" for reflections (don't forget to specify
>>> "ior"), or "metallic on" where applicable, and always use 0.0 for the
>>> minimum reflection (or leave it out, specifying the maximum reflection
>>> only).
>>
>> If you are using fresnel, is it valid (from a PBR point of view) to even
>> scale the results using a maximum reflection other than 1?
>
> Absolutely - if, for instance, your surface is littered with
> non-specular material at a microscopic level. Fine rust on iron steel,
> for instance, or a thin coating of dust.
>
> In those cases it might be better, however, to use an average of two
> materials.
>
What about plastic? It reflects, but it's not highly reflective. I don't
think I would go higher than 0.5 maximum reflection on plastic.
--
-Nekar Xenos-
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
>>> If you are using fresnel, is it valid (from a PBR point of view) to even
>>> scale the results using a maximum reflection other than 1?
>>
>> Absolutely - if, for instance, your surface is littered with
>> non-specular material at a microscopic level. Fine rust on iron steel,
>> for instance, or a thin coating of dust.
But are you sure simply scaling down the Fresnel reflection term in
those cases gives a physically correct result for those materials?
>> In those cases it might be better, however, to use an average of two
>> materials.
Yes that's my concern, that if you are using the reflection scaling to
"fake" a different effect (roughness, absorbtion or scattering etc) then
it *might* not be physically correct to just scale it.
In other words, if you created a geometrically microscopic rough surface
(or added physical dust, sub-surface scattering or whatever) and
rendered it with max reflection 1, would it be possible to get the same
result by rendering a perfectly smooth, clean surface with max
reflection set to some lower value?
> What about plastic? It reflects, but it's not highly reflective. I don't
> think I would go higher than 0.5 maximum reflection on plastic.
Agreed completely, but does using the Fresnel equations to calculate
reflection (which gives an absolute value) and scaling the result to
simulate some other effect (surface roughness, sub-surface scattering
etc) give a physically correct result? Or is it just a "fudge factor" to
give something that looks correct?
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 3-7-2015 10:34, scott wrote:
>>>> If you are using fresnel, is it valid (from a PBR point of view) to
>>>> even
>>>> scale the results using a maximum reflection other than 1?
>>>
>>> Absolutely - if, for instance, your surface is littered with
>>> non-specular material at a microscopic level. Fine rust on iron steel,
>>> for instance, or a thin coating of dust.
>
> But are you sure simply scaling down the Fresnel reflection term in
> those cases gives a physically correct result for those materials?
>
>>> In those cases it might be better, however, to use an average of two
>>> materials.
>
> Yes that's my concern, that if you are using the reflection scaling to
> "fake" a different effect (roughness, absorbtion or scattering etc) then
> it *might* not be physically correct to just scale it.
>
> In other words, if you created a geometrically microscopic rough surface
> (or added physical dust, sub-surface scattering or whatever) and
> rendered it with max reflection 1, would it be possible to get the same
> result by rendering a perfectly smooth, clean surface with max
> reflection set to some lower value?
>
>> What about plastic? It reflects, but it's not highly reflective. I don't
>> think I would go higher than 0.5 maximum reflection on plastic.
>
> Agreed completely, but does using the Fresnel equations to calculate
> reflection (which gives an absolute value) and scaling the result to
> simulate some other effect (surface roughness, sub-surface scattering
> etc) give a physically correct result? Or is it just a "fudge factor" to
> give something that looks correct?
>
I don't know, but in all these cases different from the /simple/
reflective surfaces, we need some good working examples demonstrating
the properties. I confess that this is too difficult for me - and
probably most people - to do and expect them from our own gurus :-) I
have also difficulties visualising an averaged texture or a layered
texture staying within the properties boundaries.
--
Thomas
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
> I don't know, but in all these cases different from the /simple/
> reflective surfaces, we need some good working examples demonstrating
> the properties. I confess that this is too difficult for me - and
> probably most people - to do and expect them from our own gurus :-) I
> have also difficulties visualising an averaged texture or a layered
> texture staying within the properties boundaries.
What really would be ideal would be some macros to use for various
groups of materials (glasses, metals, plastics, paints etc) with
parameters designed such that no matter what values you give you are
guaranteed a physically correct material.
I'm not a regular user of POV anymore so it's all too easy for me to get
one number "wrong" and then I don't get a physically correct material.
If there were some macros-for-dummies then this whole problem would be
avoided and would surely lead to much higher quality work from all
non-experts.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Am 03.07.2015 um 05:08 schrieb Nekar Xenos:
>>> If you are using fresnel, is it valid (from a PBR point of view) to even
>>> scale the results using a maximum reflection other than 1?
>>
>> Absolutely - if, for instance, your surface is littered with
>> non-specular material at a microscopic level. Fine rust on iron steel,
>> for instance, or a thin coating of dust.
>>
>> In those cases it might be better, however, to use an average of two
>> materials.
>>
>
> What about plastic? It reflects, but it's not highly reflective. I don't
> think I would go higher than 0.5 maximum reflection on plastic.
For plastics - and actually any material that's neither metallic nor
coated - I think heavily blurred reflections and a well-chosen ior are
the key, not reducing the reflection maximum.
With a high ior, the maximum reflection only occurs when viewing the
material almost edge-on. And with blurred reflections, even there the
maximum isn't truly achieved, as the effective reflection brightness is
tuned down by averaging in reflections at a less shallow effective angle.
BTW, the ior of most plastics is in the range from 1.5 to 1.6.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Am 03.07.2015 um 10:34 schrieb scott:
>>>> If you are using fresnel, is it valid (from a PBR point of view) to
>>>> even
>>>> scale the results using a maximum reflection other than 1?
>>>
>>> Absolutely - if, for instance, your surface is littered with
>>> non-specular material at a microscopic level. Fine rust on iron steel,
>>> for instance, or a thin coating of dust.
>
> But are you sure simply scaling down the Fresnel reflection term in
> those cases gives a physically correct result for those materials?
If it's soot, then yes (provided you also tune down the diffuse term);
any other stuff mixed in, and things get more complicated, hence my
recommendation:
>>> In those cases it might be better, however, to use an average of two
>>> materials.
>> What about plastic? It reflects, but it's not highly reflective. I don't
>> think I would go higher than 0.5 maximum reflection on plastic.
>
> Agreed completely, but does using the Fresnel equations to calculate
> reflection (which gives an absolute value) and scaling the result to
> simulate some other effect (surface roughness, sub-surface scattering
> etc) give a physically correct result? Or is it just a "fudge factor" to
> give something that looks correct?
For surface roughness, "roughness" is the POV-Ray parameter to tweak;
this also tunes down the brightness of individual pixels in highlights
(provided you use the "albedo" keyword) and reflections (provided you
also use the "roughness" keyword in the reflection block), by spreading
the highlights over a larger area (so much that you might not even
notice the specular reflection anymore), but just tuning down the
maximum brightness obviously doesn't get you the same effect, as it
leaves reflections crisp and sharp.
Sub-surface scattering has nothing to do with specular reflections - to
the contrary: It is the result of all the light that is /not/ reflected
in a specular manner (which is to say, at the object's surface). As a
matter of fact, sub-surface scattering (in a very simple case) is what
the traditional "diffuse" mechanism models.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
|
|
