POV-Ray : Newsgroups : povray.binaries.images : Backward Forward Raytracing(?) Server Time
1 Aug 2024 16:32:35 EDT (-0400)
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From: triple r
Subject: Backward Forward Raytracing(?)
Date: 9 Apr 2008 23:35:01
Message: <web.47fd8a6d74f49bc3ae42298f0@news.povray.org>
With such nice results going around I wanted to give this a try.  Here's the
image along with the full (!) implementation.  Feel free to laugh; just don't
say it doesn't work.  In short, it's just a modification for diffuse
reflection--so I hope you aren't too attached to color or specular reflection.

- Ricky


From lighting.cpp (line 2736):

e3[X]= 0.798698855654525;    //<--chosen with random number
e3[Y]=-0.402578539654782;    //generator.  Guaranteed to be
e3[Z]=-0.974274249331249;    //random every time. (#221) ;-)
VCross(e2,Jitter_Normal,e3); //set up a surface-normal
VNormalize(e3,e2);           //coord system at the point
VCross(e2,Jitter_Normal,e3); //of interest.
r1=sqrt(drand48());          //project the unit disc onto the
th=2.0*M_PI*drand48();       //unit sphere to get the proper
x1=r1*cos(th);               //distribution of diffusely
x2=r1*sin(th);               //reflected random rays
y1=sqrt(1.0-r1*r1);
VLinComb3(New_Ray.Direction, x1, e2, x2, e3, y3, Jitter_Normal);


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Attachments:
Download 'room2.jpg' (100 KB)

Preview of image 'room2.jpg'
room2.jpg


 

From: Thomas de Groot
Subject: Re: Backward Forward Raytracing(?)
Date: 10 Apr 2008 03:30:39
Message: <47fdc21f$1@news.povray.org>
I think this is very nice (cute dog too). Still a bit too grainy, but OTOH, 
that adds some character too, like an old black and white photograph.

Thomas


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From: triple r
Subject: Re: Backward Forward Raytracing(?)
Date: 11 Apr 2008 13:20:00
Message: <web.47ff9d40604c5254ae42298f0@news.povray.org>
"Thomas de Groot" <t.d### [at] internlDOTnet> wrote:
> I think this is very nice (cute dog too). Still a bit too grainy, but OTOH,
> that adds some character too, like an old black and white photograph.
>
> Thomas

Yes, the graininess is just a testament to my impatience as it only took a
couple hours to render.  I don't know how to add colors without a more
substantial patch.   But I'm curious to know:  is this path tracing?  As I
said, I just replaced the usual specular reflection with a random diffuse
reflection.  The only lighting in the scene is a sky_sphere outside and a touch
of ambient on the blinds.  Everything else is just a reflection.  If it is path
tracing, then I didn't realize it was so simple.  If not, then it's at least a
nice effect.

 - Ricky


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From: triple r
Subject: Re: Backward Forward Raytracing(?)
Date: 11 Apr 2008 13:25:00
Message: <web.47ff9e23604c5254ae42298f0@news.povray.org>
"triple_r" <nomail@nomail> wrote:
> The only lighting in the scene is a sky_sphere outside and a touch
> of ambient on the blinds.

Oh, and to clarify, there's of course no radiosity or light sources.  The time
spent tweaking the lighting went from a couple hours with lots of tricks down
to about five minutes.

 - Ricky


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From: Sven Littkowski
Subject: Re: Backward Forward Raytracing(?)
Date: 8 May 2008 00:54:43
Message: <48228793$1@news.povray.org>
Well, I think, that image has some interesting atmosphere. I like it. 
Outside a hot, bright day, but being inside (maybe after some swimming) in 
the cool shadow. I really like your creation, Ricky.

Sven



"triple_r" <nomail@nomail> schrieb im Newsbeitrag 
news:web.47fd8a6d74f49bc3ae42298f0@news.povray.org...
> With such nice results going around I wanted to give this a try.  Here's 
> the
> image along with the full (!) implementation.  Feel free to laugh; just 
> don't
> say it doesn't work.  In short, it's just a modification for diffuse
> reflection--so I hope you aren't too attached to color or specular 
> reflection.
>
> - Ricky
>
>
> From lighting.cpp (line 2736):
>
> e3[X]= 0.798698855654525;    //<--chosen with random number
> e3[Y]=-0.402578539654782;    //generator.  Guaranteed to be
> e3[Z]=-0.974274249331249;    //random every time. (#221) ;-)
> VCross(e2,Jitter_Normal,e3); //set up a surface-normal
> VNormalize(e3,e2);           //coord system at the point
> VCross(e2,Jitter_Normal,e3); //of interest.
> r1=sqrt(drand48());          //project the unit disc onto the
> th=2.0*M_PI*drand48();       //unit sphere to get the proper
> x1=r1*cos(th);               //distribution of diffusely
> x2=r1*sin(th);               //reflected random rays
> y1=sqrt(1.0-r1*r1);
> VLinComb3(New_Ray.Direction, x1, e2, x2, e3, y3, Jitter_Normal);
>
>


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From: triple r
Subject: Re: Backward Forward Raytracing(?)
Date: 8 May 2008 08:30:00
Message: <web.4822f22d604c5254dcb320720@news.povray.org>
"Sven Littkowski" <sven [] jamaica-focus [] com> wrote:
> Well, I think, that image has some interesting atmosphere. I like it.
> Outside a hot, bright day, but being inside (maybe after some swimming) in
> the cool shadow. I really like your creation, Ricky.
>
> Sven

Thanks, but just a lighting test ;-).  See original here:

http://news.povray.org/povray.binaries.images/thread/%3Cweb.47f617807305684bae42298f0%40news.povray.org%3E/

 - Ricky


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