Among other things, Paris saw fit to write:

> Pov-ray uses a shading model called PHONG in the
> literature.   It models a perfect diffuse reflector that does not really
> exist in reality.   What PHONG most closely resembles is the BRDF for
> plastic, and objects rendered with this model tend to all look like
> plastic.

No, POV-Ray *can* use Phong, but doesn't need to. You can specify "diffuse",
"brilliance", "specular", "phong", "reflection", "fresnel"... No need to
use Phong if you don't want to. Moreover, you can use micronormals to
simulate effects which, in reality, are due to micronormals as well. If you
want to simulate plastic, use Phong. If you don't like it, don't use it.

> Adding specular highlights to pov-ray's phong creates a shiney plastic
> texture.  Attempting to make it look like glass always tends to look like
> plexi-glass.  The reason is simple.  Physically-based rendering models of
> glass use a fresnel term.

Don't add specular and phong, use one of them. You want Fresnel? use fresnel
in the reflection block.

-- 
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby

Post a reply to this message

Paris wrote:
> I've decided to start a new thread instead of adding to the very large
> thread that exploded from my last post.   The messages ended up deviating
> from the original points anyway.

So you start a new thread because you don't want to address the issues 
raised by those who replied.

And now you repeat the same claims again - starting with a completely 
wrong explanation of a BRDF and not getting much better later.  Just 
repeating a wrong claim does not make them right.

The examples of non-POV-Ray renders you have shown show nothing 
impossible in POV-Ray.  Most of them can be easily made in much higher 
quality with POV-Ray.

> The main point of my original post (and this one) shall be repeated here for
> emphasis.  My point is that Pov-Ray is lagging behind commercial packages
> in terms of photorealism.   I then gave some examples, and suggestions for
> how we can get Pov-Ray back into a competition with these packages.

No, you gave a few links to images.  Real examples demonstrating your 
claim would require explanation what technique they demonstrate, why 
this is realistic and why there is no way to achieve the same effect in 
POV-Ray.  Of course this would require some actual in-depth knowledge of 
POV-Ray.  Note i am not saying it is impossible to find such techniques 
but with your superficial way of looking at things you won't have much 
chance.

You can easily find examples for car paint, fur, bloom or anisotropic 
highlights that look at least as realistic as the images you showed by 
searching p.b.i.

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 23 Sep. 2004 _____./\/^>_*_<^\/\.______

Post a reply to this message

In article <web.41d656e4221a9eda765651f90@news.povray.org> , "Paris" 
<par### [at] lycoscom> wrote:

> I've decided to start a new thread instead of adding to the very large
> thread that exploded from my last post.   The messages ended up deviating
> from the original points anyway.

Just the perfect reason to start a new thread two weeks later while not
having replied to a *single* post in the thread you originally created.

> Some of the things people had posted in their replies were just patently
> false.  I will try to address some of these things first, and I will not
> mention names, since this is a discussion forum.

So you just repeat your nonsense again, ignoring everything you were told
and try to start the same discussion over again. Great!

I no longer give you the benefit of the doubt.  Trolls are not welcome in
these newsgroups.  Please consider this as a last warning.

    Thorsten Froehlich, POV-Team

____________________________________________________
Thorsten Froehlich
e-mail: mac### [at] povrayorg

I am a member of the POV-Ray Team.
Visit POV-Ray on the web: http://mac.povray.org

Post a reply to this message

Jellby <jel### [at] yahoocom> wrote:
> No, POV-Ray *can* use Phong, but doesn't need to. You can specify "diffuse",
> "brilliance", "specular", "phong", "reflection", "fresnel"... No need to
> use Phong if you don't want to.

  Btw, don't confuse the keyword 'phong' with the "phong illumination model",
which are rather different things.

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

Post a reply to this message

Paris <par### [at] lycoscom> wrote:
> Physically-based rendering models of glass use a fresnel term.

  Could you please explain what 'fresnel' in POV-Ray (see the documentation
for details) does differently than what you want?

> Someone's reply to my take on pov-ray's global illumination was not only
> rude and uncooth, but it was wrong as well.   Pov-ray "gathers" global
> illumination by shooting out rays in a random way based loosely on a stored
> table of directions.  Every single piece of literature on 3d graphics
> rendering calls this method *DISTRIBUTED RAY TRACING*.  (simply google
> "distributed ray tracing")  Pov-ray does not use monte carlo based
> path-tracing to simulate global illumination.

  Could you please explain us what is the difference between a
monte carlo based global illumination technique and distributed
raytracing?

>  The person who replied to me
> (whose name I will leave out here) was just dead wrong on this issue.
> Distributed ray tracing suffers from shooting rays often into completely
> dark areas of the scene.  This is a wasted calculation since just
> rgb<0,0,0> rays don't contribute anything at all to the shaded point
> mathematically.

  And how does a monte carlo method help with this problem?

  Also, you wouldn't mind explaining us how can you determine a part
of the scene is so dark that it does not contribute in the illumination
of a certain part of the scene without actually looking what is the
illumination in that dark part of the scene?

>    There is no way to completely avoid this from happening,
> but there are methods to make it happen less, such as bi-directional
> path-tracing techniques that use at least some information about the light
> coming out of the light sources.

  But light sources are not the only elements affecting the lighting of
a scene. Some surfaces may have brightness on their own, and there can
be other illuminating effects in the scene as well (eg. media).

> Someone, in their reply, asked me if I "realized the cost" of implementing
> this.  I'm not sure what that meant.  It's only slightly slower in terms of
> CPU clock cycles needed, because the slowest parts of ray-tracing (in
> general) is calculating ray intersections with surfaces, not in the
> shading.  Anyone should realize that spectral integration is a different
> *SHADING* technique not a radical overhall of the geometry.  Dispersion in
> prisms is only ONE of the things this technique gives.

  Could you please explain us how to calculate the dispersion of a prism
so that the rendering becomes "only slightly slower in terms of CPU
clock cycles needed"?

  Btw, do you have any measurement data showing that the heaviest part of
raytracing is the ray intersection process in the average scene?

> Actually that picture does not
> look like brushed metal at all to me.

  Isn't that a question of opinion?
  Your opinion seems prejudiced in that you are probably thinking like
"POV-Ray does not use this 'physically accurate model' I am thinking of
and thus this image does not look like brushed metal".

> Already POV-ray
> can calculate photorealistic blooms around light sources using atmosphere,
> but not yet around bright surface highlights. For an idea of what a bloom
> is, look at the bell tower in this image:

> http://paris1839.tripod.com/computers/afterain.jpg

  You do realize that image has been rendered with POV-Ray?

> My point is that Pov-Ray is lagging behind commercial packages
> in terms of photorealism.

  POV-Ray is not a commercial package, so what do you want?
  If you are not happy with it, then either use one of your commercial
packages (which you will pay for, naturally, if you have even the
smallest amount of honesty), or change POV-Ray to suit your needs (the
source code is available for you to modify).

  If you really want for other people to implement what you can't or
have no time to, then you might better revise your tone of voice and
get some more specific information on things.

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

Post a reply to this message

From what I can see, what you are really asking for is not the functionality
of these items, because most, if not all of these things CAN be done. You
might have to work at them. What you want is a button you can push, and
have all the work done for you. 'Look, I made a box... and now it looks
like cement! Yay!' If you want it to be easy, POV is not the thing for you.
But if you're willing to read the documentation, and look at patches, you
might have a little more luck in these conversations. F'rinstance, the
MegaPov HDR patch CAN output HDR images. If you download HDRShop from
Debevec, you can alter the exposure.
At least ask questions, rather than make statements.

'Is there a way to make brushed metal?'

would probably recieve the response,

'There are several. You can try averaging many slightly rotated
micronormals. The trick is to get circlar grooves. Take a look at a vinyl
record. This is slow, but very realistic, and gives you quite a bit of
control. (In fact, this method will even give you correctly holographic
results, as I recall).  Also, I believe there is a fairly fast brushed
metal on runevision.com, but I haven't tried it.'

Which is probably much more helpful, and it doesn't even involve people
hating you.

-S

Post a reply to this message

Paris wrote:
> I've decided to start a new thread instead of adding to the very large
> thread that exploded from my last post.   The messages ended up deviating
> from the original points anyway.

WHich is ok, as your original points only point to your lack of ability 
with POV-Ray.  I have seen far more works here, done with POV-Ray, than 
I have seen done with your megabuck modelers, that look realistic.

Global lighting, try Poser if you want to find out what an abortion 
global lighting can be.  It is so restricted as to be totally useless, 
and is the reason I don't render anything in poser.  I *like* having 
good control over the lighting, and being able to reproduce the effects 
from a single source, rather than "the entire heavens radiate in all 
directions."  If I want that effect, which I don't, I'll put everything 
inside a hollow white sphere to get it, which is hardly worth the trouble.

Brushed metal, being as I make real brushed metal on occasion, I am a 
toolmaker, I think I know what's realistic and what isn't, NONE of them 
you can come up with are.

Final, it's very easy to criticize when you're not involved with the 
programming.  If you aren't satisfied with it, use something like 3DMAX. 
  Or maybe they just dont bitch because they're ashamed to admit that 
they spent the kilobucks for something that still won't do what they 
*think* it should.

OH, BTW, "Plonk."

Post a reply to this message

Warp wrote:
>>http://paris1839.tripod.com/computers/afterain.jpg
>   You do realize that image has been rendered with POV-Ray?

ooooooh...I wanna know how that was done *drool*

-- 
Tim Cook
http://home.bellsouth.net/p/PWP-empyrean

-----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------

Post a reply to this message

Tim Cook wrote:
> Warp wrote:
> 
>>> http://paris1839.tripod.com/computers/afterain.jpg
>>
>>   You do realize that image has been rendered with POV-Ray?
> 
> 
> ooooooh...I wanna know how that was done *drool*
> 


Third place in the July-August 1998 IRTC Stills competition:
http://www.irtc.org/stills/1998-08-31.html

Description:
http://oz.irtc.org/ftp/pub/stills/1998-08-31/afterain.txt

Source:
http://oz.irtc.org/ftp/pub/stills/1998-08-31/afterain.zip

Post a reply to this message

Paris, a couple of the things you showed can be done on POV-Ray as is.

> CAR PAINT------
> In contra to the person who replied to me, car paint is not "just paint".
> Car paint can sometimes contain tiny glitters in laquer that sparkle when
> an object is turned in the light.  It also has a sort of metallic sheen
> that the phong model cannot simulate that falls off to nearly black at
> shallow viewing angles.  CEBAS's FinalRender simulates all of these.   See:
>
> http://www.finalrender.com/products/images/finalShaders/fR-carpaint_01.jpg
>
> Notice the "falling off to black" at shallow angles.  It's hard to notice at
> first but when you see it it should look like a very quick turn to black at
> the edges of curves.   Pov-ray cannot simulate car paint.  But like I said
> in my original post, it would be nice to see in future versions.
Its been said by others, but Tek has made an awesome metallic paint macro.
Check P.B.S-F to find it

> FUR/SUEDE/VELVET-----
> Hair is implementable with tricks, but suede and tight, tiny fur is a
> procedural texture requiring code all to itself.   Fur will often have
> anamolous dark spots on the insides of concave surfaces, where the 'hairs'
> are more bunched togethor.  And it will look slightly brighter on convex
> parts of a surface since the 'hairs' are less dense.  In suede, this
> happens at the microfacet level, so it cannot be simulated ad-hoc with
> millions of tiny objects.   Again, CEBAS's FinalRender gives the most
> striking example I've ever seen which contains all of the attributes I
> mentioned:
>
> http://www.finalrender.com/products/images/finalShaders/fR-DistanceFur_02.jpg
>
> To reiterate, it would be nice to see such things implemented in future
> versions of POV.  But I make no demands.
You don't say why it can't be done with current POV-Ray. Megapov has a fur
feature and Rune also made a very good fur texture. I don't see why it
can't be done now.

Brushed metal has been done before. Jaime Vives Piqueres's "Still With
Bolts" is an excelent example of photorealistic brushed metal. You just
need to average randomly rotated normals.

Also, megapov has an exposure feature to it. I don't see how it can't
perform the same function you were suggesting.

>http://www.maxwellrender.com/indexeng.html
All of the pictures you showed can be done on POV. Some of them can be done
better (that "brushed metal" tire rim being a prime example). Its been said
before, POV-Ray is free and open-source. Despite it being supported by
people in their free time, its still comparable, and sometimes better, than
those slick-looking commerical products. The only software you showed that
stuck out in my mind was Maxwell, and thats not coming out for a while.

A lot of your ideas do sound interesting, such as spectral integration and
BRDF. However, it sounds like you're going to have to develop them yourself
if you want them done, or at the very least give more detail into how they
can be implemented. After all, they're your suggestions, so its not
unreasonable to want you to do a good amount of work.

Post a reply to this message