Paris <par### [at] lycoscom> wrote:
> Pov-Ray is lagging farther and farther behind commercial rendering software
> in terms of photo-realism.

  You get what you pay for, pal.

> 1.  The phong model is outdated now.

  You can do quite pretty stuff with povray's fresnel highlights and
variable reflection. It may require some fine-tuning by hand, but
I wouldn't call it so "outdated".

> 2.  Pov-ray does not have hair, fuzz, fur, or suede textures.  Brushed metal
> would be nice also. And car paint too...

  Please post the algorithms on how they are done with raytracing and
I'm sure they will find their way into povray.

> There are many textures out there that can only be implemented
> using path-tracing techniques, such as very shiney, partially-reflective
> gold.  A few others are glossy reflections (blurred reflections) and
> frosted glass.

  Although not trivial, you can do blurred reflections and refractions
(using stochastic raytracing) with the current povray. It's not even
hopelessly slow.

> Reflected parts of the scene do not have the radiosity calculation
> performed on them.

  Not true. Are you using POV-Ray 3.1 or something?

-- 
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 -

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I won't waste my time dissecting everything written in this posting but 
in case there are people here who consider taking this posting as a 
valuable statement i will as an example analyze the first point:

> 
> 1.  The phong model is outdated now.   

It is not clear what is actually meant with "phong model" here but it 
has to be assumed it is the method of calculating specular highlights 
introduced by Phong (this is the only feature related to the name Phong 
that exists in POV-Ray).  Now the above statement is certainly not true 
since this technique is frequently used by artists (and not only in 
POV-Ray of course).

> The next release of pov-ray should
> use physically-based BRDFs, and only keep the phong model around for
> compatability.  

This implies POV-Ray's use of the "phong model" (see above) is more than 
one feature of many that can be used or not used which is not the case. 
  What "physically-based BRDFs" are is not explained and neither why the 
"phong model" and other techniques in POV-Ray are not physically-based.

> Phong makes everything look like plastic, including what we
> have been calling "glass".

This is obviously wrong but even if it wasn't this would not be a very 
valuable statement (like 'using red light makes everything red').

> The difference between pov-ray glass and
> physically-based glass in other packages is STRIKING.

This is pointless without examples (and of course wrong - i have seen 
dozens of very realistic glass renders made with POV-Ray).

> Real glass has a
> fresnel effect, where shallow-angled light reflected from the surface tends
> more towards a perfect mirror.

Ah - a new name: Fresnel.  Last time i checked this was a reserved 
keyword in POV-Ray so there has to be some feature related to Mr. Fresnel...

> This also happens in real life.  My
> suggestion is allow BRDFS for those who need them, and base the
> documentation around the Phong model as usual.

The use of the word 'BRDF' is strange here - the "phong model" (if meant 
as explained above) is a BRDF as well.  Apart from that the idea to 
introduce a new feature ("allow BRDFS" - whatever this should mean) but 
not document it is just ridicuous.

Christoph

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

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In article <web.41bf577e1db2d3fb765651f90@news.povray.org> , "Paris" 
<par### [at] lycoscom> wrote:

> Pov-Ray is lagging farther and farther behind commercial rendering software
> in terms of photo-realism.   There are many reasons why this is the case,
> but some reasons are more evident and more easily solved than others.

I will give you the benefit of the doubt and assume you are just clueless
and not a troll.

> 1.  The phong model is outdated now.   The next release of pov-ray should
> use physically-based BRDFs, and only keep the phong model around for
> compatability.  Phong makes everything look like plastic, including what we
> have been calling "glass".   The difference between pov-ray glass and
> physically-based glass in other packages is STRIKING.  Real glass has a
> fresnel effect, where shallow-angled light reflected from the surface tends
> more towards a perfect mirror.

I would suggest to RTFM before making false statements about available
features in POV-Ray...
<http://www.povray.org/documentation/view/3.6.1/348/>


> 2.  Pov-ray does not have hair, fuzz, fur, or suede textures.  Brushed metal
> would be nice also. And car paint too...  I won't ask for
> subsurfacescattered flesh just yet, it tends to be very time-consuming to
> implement.   There are many textures out there that can only be implemented
> using path-tracing techniques, such as very shiney, partially-reflective
> gold.  A few others are glossy reflections (blurred reflections) and
> frosted glass.

Again, maybe you should RTFM.  And brushed metal, well, can it get more
brushed than
<http://news.povray.org/povray.binaries.images/thread/%3Cweb.419777b7897a5e5
4b0aac12c0@news.povray.org%3E/>?

Apart from that, you do realise that hair and fur are not textures, right?
And car paint, how did you get the idea POV-Ray cannot render something as
trivial as car paint, which is hardly anything else but paint?

> 3.  Povray uses distributed ray-tracing to simulate global illumination.

Distributed ray-tracing is a supersampling technique (antialiasing), so it
has nothing to do with global illumination.

> Reflected parts of the scene do not have the radiosity calculation
> performed on them.  I have found this to be highly frustrating.  (Simply
> create a radiosity room and stick a large reflecting ball in the middle to
> see what I mean.)   The speed-ups to this method leave even the most
> advanced users scratching their heads.  Ive been using pov-ray since it was
> named DKB-Trace, and honestly, I'm still not sure that "minimum_reuse"
> means under the radiosity settings.

Clearly you have not, otherwise you would know that POV-Ray's radiosity was
added in POV-Ray 3.0 many years after DKB-Trace.  And if you cannot use it,
well, it certainly ain't trivial but that _you_ cannot use it hardly says
anything about POV-Ray's quality but only about _your_ abilities.  And given
your other statements so far, I have serious doubts in those...

>  If you think about what distributed
> ray-tracing does, you will notice it works by tracing rays into DARK PARTS
> of the scene, hoping for a swath of light.   It doesnt take a professor to
> realize that this is a wasted calculation.   Tracing a ray into a dark part
> of the scene will mathematically never make a difference in the shaded
> pixel.

No clue probably defines your statement best, POV-Ray "radiosity" is a Monte
Carlo ray-tracing technique, so how you got the idea that it has anything to
do with sampling dark areas of a scene is beyond me.  The algorithm
implemented is based on "A Ray Tracing Solution for Diffuse Interreflection"
by Ward, Rubinstein, and Clear in the Siggraph 1988 Proceedings.

> 4.  There are other physically-based methods out there that turn ray-tracing
> on its head.

Ah, you mean the "real-world"?  Sure, that will always be better than
ray-tracing.

>  I pretty much expect future versions of Pov-ray to move away
> from the phong model (part 1) and implement a few BRDFs for popular
> surfaces, but other methods would be nice to see also, which I have less
> faith in.   There are ways to calculate light in rendering in which you do
> not even use RGB color space.   These algorithms use spectral integration,
> and create a large picture out of pixels that are colored with the
> SPECTRUM, rather than RGB triples.

You do realise the cost of using a non-RGB implementation?  There is a
reason why there are special programs that allow exact simulation of the
wave effects of light.  Unless you need it, POV-Ray can simulate the effect
just like all "professional" rendering software does.  I guess in all your
cluelessness you are talking about dispersion, so maybe RTFM
<http://www.povray.org/documentation/view/3.6.1/415/>.

> 5.  Even without spectral integration, you can render in RGB space and still
> do EXPOSURE simulations.  (Usually its the case that exposure simulation is
> not used unless a certain amount of "energy" is calculated to be passing
> through the cameras' aperture, but it can be done ad hoc in RGB space also,
> by fanagling.)  This basically works by storing floating point triples into
> each pixel, none of which are CLIPPED or "tuned down"  to fit into  0.0 -->
> 1.0.

I believe you want HDR image output.  There is a not a standard format for
that, but your talk about floating-point RGB values clearly shows you know
exactly nothing about what you are talking about.  And no, I will not bother
to explain.

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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"Thorsten Froehlich" <tho### [at] trfde> wrote in message
news:41bf6e0c$1@news.povray.org...
> In article <web.41bf577e1db2d3fb765651f90@news.povray.org> , "Paris"
> <par### [at] lycoscom> wrote:
>

snip

> Again, maybe you should RTFM.  And brushed metal, well, can it get more
> brushed than
>
<http://news.povray.org/povray.binaries.images/thread/%3Cweb.419777b7897a5e5
> 4b0aac12c0@news.povray.org%3E/>?
>

yeah, that's a freakin awesome texture, by the way.

> Apart from that, you do realise that hair and fur are not textures, right?
> And car paint, how did you get the idea POV-Ray cannot render something as
> trivial as car paint, which is hardly anything else but paint?
>


I can only assume he means paint that appears different based on the angle
with which it is viewed. Someone did a *very* nice animation exhibiting this
in p.b.animations a while back. I'm not sure what version of POV or patches
it used though. It was exactly car paint though. I can't find it now though
:/

-ross

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Thorsten Froehlich wrote:

> 
> I will give you the benefit of the doubt and assume you are just clueless
> and not a troll.
> 

Blink

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Paris wrote:
> Pov-Ray is lagging farther and farther behind commercial rendering software
> in terms of photo-realism.   There are many reasons why this is the case,
> but some reasons are more evident and more easily solved than others.
> 
> 1.  The phong model is outdated now.   The next release of pov-ray should
> use physically-based BRDFs

Ok, I'll leave it to the technical whiz types to disassemble the rest of 
this, 'cause you already lost me...

What's a BRDF?

Bouncing Recalcitrant Damn Fool?
Blonde Receptionists Dating Foundation?
Business Requirements Driving Failure?
Blatantly Ridiculous Dumb Fluff?
Bush Regime's Dastardly Fixation?
Bored Reactionary Dropping FUD?
Blue Rhinoceros Drinking Floorwax?
Bucolic aRDvaark Fainting?
Belatedly Realized Dangerous Flatulence?

RG - dammit Jim, I'm an artist not a rocket scientist

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On Wed, 15 Dec 2004 00:17:38 -0800, gonzo <rgo### [at] lansetcom> wrote:
> What's a BRDF?

Actually... there is not many unrollings of this acronym.

http://www.acronymfinder.com/af-query.asp?Acronym=BRDF

:-)

ABX

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news:cpnq4s$sj8$1@chho.imagico.de...

> Ah - a new name: Fresnel.  Last time i checked this was a reserved
> keyword in POV-Ray so there has to be some feature related to Mr.
Fresnel...

Other software call "fresnel" a shader that allow texture attribute to vary
according to the viewing angle of a 3D surface. Of course this is can be
done with POV-Ray for reflection and, for other properties, with the aoi
patch in Megapov (and it can be partially simulated in regular POV with
slope). I guess a future POV 4.0 could unify this with a single
property/keyword.

G.

-- 

**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters

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Gilles Tran wrote:
> 
> Other software call "fresnel" a shader that allow texture attribute to vary
> according to the viewing angle of a 3D surface.

In fact all shaders POV-Ray offers (although the term 'shader' is 
possibly misleading in case of a raytracer) except diffuse vary the 
color depending on the viewing angle.  It is the very definition of a 
diffuse surface that the appearance does not depend on the viewing 
angle.  The fresnel formulas specify a certain type of angle dependance 
which well describes the reflectance of an ideal specular surface and 
for this purpose it is used in POV-Ray.  To use it elsewhere, for 
example to vary the surface's own color pattern is possible (via aoi 
pattern) but would only serve artistic purposes without physical 
background so there isn't a predefined feature (like a fresnel waveform 
for use with aoi) in POV-Ray.

Christoph

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

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I think that the others here have just about covered the important points,
but I'm going to add my two cents a quarter and a nickel anyway.  It's
obvious to me that you didn't do your homework before posting this farce.

One of the first things you learn in English 101 - Or any english class
where writing is a major focus - is that you should always define your
abbreviations before you use them if they are not very commonly known.

For those of us here who don't know, but would like to, a BDRF is a
Bi-Directional Re-distribution function, and a quick search of the top hits
on Google will render more information.

That said:

I've been working with POV-Ray for about seven years now, but it's only
within the last four or so that I've begun to produce anything really
worthwhile, and, while I've never done it myself, I've seen others make
some remarkably realistic images with POV (HE Day's "Drunk Patrol" simply
blows my mind.)

In the future, it would be wise for you to research any topic you're going
to write about THOUROUGHLY, BEFORE you go making a horse's ass of yourself.

Regards,

ADB

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