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From: Paragon
Subject: Blurred reflections
Date: 6 Jul 2002 17:23:00
Message: <3d275fb4@news.povray.org>
I am experimenting with using blurred reflections and am using the method
Warp lists in his PovQandT on his web site.  But rendering with this
technique takes an extremely long time to render.  What other proven
techniques are there to create blurred reflections (that are preferrably
faster to render)?

...too bad POV-Ray doesn't support blurred reflections like MegaPOV does

----------------
Here is the technique listed in the PovQandT:

#declare BlurAmount = .2; // How blurred the reflection should be
#declare BlurSamples = 40; // How many reflected rays to shoot

object
{ MyObject
  texture
  { average texture_map
    { #declare Ind = 0;
      #declare S = seed(0);
      #while(Ind < BlurSamples)
        [1 pigment { ObjectPigment } // The pigment of the object here
           finish { ObjectFinish } // The finish; should have reflection
           normal
           { bumps BlurAmount
             translate <rand(S),rand(S),rand(S)>*10
             scale 1000
           }
        ]
        #declare Ind = Ind+1;
      #end
    }
  }
}

Here is how I used it (and rendering takes forever):

#declare BlurAmount = .2;
#declare BlurSamples = 20;
#declare Polished_Chrome =
   material  // Polished_Chrome
   {
      texture
      {  average texture_map
         {
                #declare Ind = 0;
                #declare S = seed(0);
                #while( Ind < BlurSamples)
                [1 pigment
                   {
                     color rgb <0.2, 0.2, 0.2>
                   }
                   finish
                   {
                     ambient 0.1
                     diffuse 0.7
                     brilliance 6.0
                     phong 0.8
                     phong_size 120.0
                     reflection 0.6
                   }
                   normal
                   {
                     bumps BlurAmount
                     translate <rand(S), rand(S), rand(S)>*10
                     scale 1000
                   }
                 ]
                 #declare Ind = Ind + 1;
                 #end
         }
      }
   }


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From: Warp
Subject: Re: Blurred reflections
Date: 6 Jul 2002 17:50:01
Message: <3d276609@news.povray.org>
Paragon <use### [at] hostcom> wrote:
> ...too bad POV-Ray doesn't support blurred reflections like MegaPOV does

  It wouldn't help much. MegaPov does basically the same thing, and it's
not any faster there.
  Using this trick, however, you can do much more than MegaPov's blurred
reflection can.

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -


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From: Christopher James Huff
Subject: Re: Blurred reflections
Date: 7 Jul 2002 14:43:24
Message: <chrishuff-1BF970.13410007072002@netplex.aussie.org>
In article <3d275fb4@news.povray.org>, "Paragon" <use### [at] hostcom> wrote:

> I am experimenting with using blurred reflections and am using the method
> Warp lists in his PovQandT on his web site.  But rendering with this
> technique takes an extremely long time to render.  What other proven
> techniques are there to create blurred reflections (that are preferrably
> faster to render)?
> 
> ...too bad POV-Ray doesn't support blurred reflections like MegaPOV does

MegaPOV uses the same basic technique, except that it just randomly 
jitters the rays. The averaged texture method is slower if you compare 
by the number of blur rays cast, but you usually don't need as many 
samples because the rays aren't purely random, and it is much more 
flexible: it can be used to simulate different shapes of bumps or ridges 
on the surface. It might be possible to make a patch that has the same 
flexibility but is as optimized as possible, it would be a bit more work 
than the MegaPOV blur but it is possible.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/


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From: Warp
Subject: Re: Blurred reflections
Date: 7 Jul 2002 19:02:34
Message: <3d28c88a@news.povray.org>
Christopher James Huff <chr### [at] maccom> wrote:
> It might be possible to make a patch that has the same 
> flexibility but is as optimized as possible, it would be a bit more work 
> than the MegaPOV blur but it is possible.

  I would bet that in pov4 we will have some way of saying in a texture
(or whatever property of the surface) things like "shoot a ray in this
direction and return me the color", which can eventually be used to make
blur-reflecting textures or whatever we like.

-- 
#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 -


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From: Ken
Subject: Re: Blurred reflections
Date: 7 Jul 2002 19:56:39
Message: <3D28D52C.D40C769F@pacbell.net>
Warp wrote:

>   I would bet that in pov4 we will have some way of saying in a texture
> (or whatever property of the surface) things like "shoot a ray in this
> direction and return me the color", which can eventually be used to make
> blur-reflecting textures or whatever we like.

And I hope pov4 doesn't become just another programmers only toy.

-- 
Ken Tyler


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From: Hugo
Subject: Re: Blurred reflections
Date: 8 Jul 2002 03:07:26
Message: <3d293a2e@news.povray.org>
> MegaPov does basically the same thing, and it's not any faster

Even when two blurred objects are close to each other and the rays ping
pong? That takes ages with the blur "trick" but the rendertime can be
considerably reduced with a low max_trace_level without any noticeable
difference.. Maybe MegaPOVs blurred reflection wouldn't change it's speed
with max_trace_level? It would be a better way then, because a scene may
have other objects that need a very high max_trace_level.

> you can do much more than MegaPov's blurred reflection can.

The best results are when the averaged normals are scaled very big, but then
the layers have a random value .. if you understand what I mean ... with
only a few layers, this does not always look good.. Besides it seems a very
big limitation that we can't apply both blur *and* an ordinary normal
pattern / image_map ... doing so does not mix well without MegaPOV.


Regards,
Hugo


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From: Warp
Subject: Re: Blurred reflections
Date: 8 Jul 2002 09:25:15
Message: <3d2992ba@news.povray.org>
Hugo <hua### [at] post3teledk> wrote:
> Maybe MegaPOVs blurred reflection wouldn't change it's speed
> with max_trace_level?

  It wouldn't make any sense if max_trace_level would not affect blurred
reflection.

> The best results are when the averaged normals are scaled very big, but then
> the layers have a random value .. if you understand what I mean ... with
> only a few layers, this does not always look good..

  You can scale the normal very small, thus getting a similar result to
MegaPov's blurred reflection. It isn't very nice either (*really* grainy).

> Besides it seems a very
> big limitation that we can't apply both blur *and* an ordinary normal
> pattern / image_map ... doing so does not mix well without MegaPOV.

  The Q&T tip describes how to use both the blurred reflection trick and a
regular normal pattern.

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -


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From: Christopher James Huff
Subject: Re: Blurred reflections
Date: 8 Jul 2002 11:16:16
Message: <chrishuff-6DA49C.10135608072002@netplex.aussie.org>
In article <3d293a2e@news.povray.org>, "Hugo" <hua### [at] post3teledk> 
wrote:

> Even when two blurred objects are close to each other and the rays ping
> pong?

The blur patch doesn't do anything special in that case. That can get 
very slow with the blur patch as well, and you need more samples to get 
fairly smooth results.


> That takes ages with the blur "trick" but the rendertime can be 
> considerably reduced with a low max_trace_level without any 
> noticeable difference.. Maybe MegaPOVs blurred reflection wouldn't 
> change it's speed with max_trace_level? It would be a better way 
> then, because a scene may have other objects that need a very high 
> max_trace_level.

There isn't any special difference between ordinary reflection and 
blurred reflection, max_trace_level behaves the same. A blur patch 
*could* do something like that, but the existing one doesn't.


> The best results are when the averaged normals are scaled very big, but then
> the layers have a random value .. if you understand what I mean ... with
> only a few layers, this does not always look good..

I don't understand. The part about using large scale normals is what 
makes the technique better than what the patch does, I don't know what 
you mean by "the layers have a random value".
With only a few layers, it doesn't look good...and the blur patch 
doesn't look good with only a few samples. Your point?


> Besides it seems a very big limitation that we can't apply both blur 
> *and* an ordinary normal pattern / image_map ... doing so does not 
> mix well without MegaPOV.

There aren't any problems with image_maps. You *can* mix normals and 
blur, it does get tricky though...a built-in feature would be simpler to 
use.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/


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From: Warp
Subject: Re: Blurred reflections
Date: 8 Jul 2002 12:19:03
Message: <3d29bb77@news.povray.org>
Christopher James Huff <chr### [at] maccom> wrote:
> There aren't any problems with image_maps. You *can* mix normals and 
> blur, it does get tricky though...a built-in feature would be simpler to 
> use.

  A builtin version would also take a lot less memory and be a tiny bit faster.
However, it would be difficult to get the same versatility with a builtin
version - it would have to be designed very carefully.
  Of course I have the feeling that we can forget that when we get pov4
some time in the distant future. My guess is that it will most probably have
some kind of way of specifying quite meticulously how a surface is colored
(something extremely similar to renderman shaders). Making any kind of
blurred reflection with that will probably be very easy.

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -


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From: Hugo
Subject: Re: Blurred reflections
Date: 8 Jul 2002 12:25:24
Message: <3d29bcf4$1@news.povray.org>
> > The best results are when the averaged normals are scaled very big, but
then
> > the layers have a random value .. if you understand what I mean ... with
> > only a few layers, this does not always look good..
>
> I don't understand. The part about using large scale normals is what
> makes the technique better than what the patch does, I don't know what
> you mean by "the layers have a random value".
> With only a few layers, it doesn't look good...and the blur patch
> doesn't look good with only a few samples. Your point?

I'll try again then. I was only talking about the reflection tricks without
Megapov. Lets say you average 5 normals, using the bump pattern scaled very
big. Then you have 5 normals, but their directions are random..

Example: You apply the blur texture on a plane and put a white sphere above
it, that is supposed to be reflected on the plane, and use a black
background.. The result with 5 averaged normals is not 5 eqaul steps between
black/white. Because the bump patterns have random values (psudo-random, to
be precise).


Regards,
Hugo


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