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Kari Kivisalo wrote:
> Surface properties are irrelevant, only the emitted energy matters.
It's the surface properties which determine the emitted energy.
> Put a sample of linoleum in a test bench and measure its
> photometric brightness at various distances. It will take a
> material considerably more exotic than linoleum to break the
> laws of physics :)
Take a chair, set it on a linoleum floor, then look at its
reflection. You don't see the entire chair.
--
Tim Cook
http://empyrean.scifi-fantasy.com
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------
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On Tue, 23 Oct 2001 12:31:16 -0400, Trevor Quayle wrote:
> Am I wrong in what I am assuming here?
Yes. The effect you see in Linoleum[1] is *exactly* reflection blurring. If
you really had a perfectly smooth Linoleum with no blurring, you'd find
that it didn't exhibit the effects you associate with Linoleum.
However, there's still a place for faded reflection in the POV toolbox. It's
definitely the case that no matter how we do it, real blurred reflection takes
a lot of horsepower. If faded reflection is good enough, there's no reason
it shouldn't be used. However, I don't think it actually works. To work,
it would need to fade based on the distance normal to the surface, not the
total distance. That's just not practical.
[1] Linoleum is - or at least was - somebody's trademark. It's only fair to
capitalize it.
--
#macro R(L P)sphere{L __}cylinder{L P __}#end#macro P(_1)union{R(z+_ z)R(-z _-z)
R(_-z*3_+z)torus{1__ clipped_by{plane{_ 0}}}translate z+_1}#end#macro S(_)9-(_1-
_)*(_1-_)#end#macro Z(_1 _ __)union{P(_)P(-_)R(y-z-1_)translate.1*_1-y*8pigment{
rgb<S(7)S(5)S(3)>}}#if(_1)Z(_1-__,_,__)#end#end Z(10x*-2,.2)camera{rotate x*90}
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On Tue, 23 Oct 2001 12:32:19 -0400, Timothy R. Cook wrote:
> Kari Kivisalo wrote:
>> Surface properties are irrelevant, only the emitted energy matters.
>
> It's the surface properties which determine the emitted energy.
>
>> Put a sample of linoleum in a test bench and measure its
>> photometric brightness at various distances. It will take a
>> material considerably more exotic than linoleum to break the
>> laws of physics :)
>
> Take a chair, set it on a linoleum floor, then look at its
> reflection. You don't see the entire chair.
Some of that is Fresnel reflection. Some of it is blurred reflection.
None of it is the inverse-square law.
--
plane{-z,-3normal{crackle scale.2#local a=5;#while(a)warp{repeat x flip x}rotate
z*60#local a=a-1;#end translate-9*x}pigment{rgb 1}}light_source{-9red 1rotate 60
*z}light_source{-9rgb y rotate-z*60}light_source{9-z*18rgb z}text{ttf"arial.ttf"
"RP".01,0translate-<.6,.4,.02>pigment{bozo}}light_source{-z*3rgb-.2}//Ron Parker
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Trevor Quayle wrote:
>
> explain how it would apply to a small object against a dark background?
You just look at the object surface and ignore the rest. One mesure
of brightness (pixel values) could be W/m^2. It doesn't change
when the size (area) of the object changes. A big object which emits
100 W/m^2 is as bright as a small object which emits 100 W/m^2.
The total energy emitted changes but not the energy/area (brightness).
This is all seen from a fixed camera distance of course.
_____________
Kari Kivisalo
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"Kari Kivisalo" <ray### [at] engineer com> wrote in message
news:3BD5A384.940229DF@engineer.com...
> Trevor Quayle wrote:
> >
> > explain how it would apply to a small object against a dark background?
>
> You just look at the object surface and ignore the rest. One mesure
> of brightness (pixel values) could be W/m^2. It doesn't change
> when the size (area) of the object changes. A big object which emits
> 100 W/m^2 is as bright as a small object which emits 100 W/m^2.
> The total energy emitted changes but not the energy/area (brightness).
> This is all seen from a fixed camera distance of course.
I actually meant the same sized object at varying distances, I can see how
what you are saying works for varying object sizes.
-tgq
>
>
> _____________
> Kari Kivisalo
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"Timothy R. Cook" wrote:
>
> Take a chair, set it on a linoleum floor, then look at its
> reflection. You don't see the entire chair.
Yes, the reflection is blurred, we know that already.
_____________
Kari Kivisalo
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Timothy R. Cook <tim### [at] scifi-fantasycom> wrote:
:> It's supposed to resemble a poor man's reflection blur.
: Actually I was thinking more along the lines of linoleum floors,
: where you only have a few inches of reflection.
That is, what he said.
--
#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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