Am Mon, 30 Oct 2006 10:16:39 -0500 schrieb Smws:

> Hi, all.
> 
> I realized I couldn't make my IRTC image in time for the competition, so
> to console myself I was modelling some other things.  I was fiddling with
> Jaime's photo-studio and some of my own models, and now I have a
> question...
> 
> In the scene, I have a blurred-reflective texture using Tim Nikias'
> method, and it renders fast for one object (sphere) and **really** slow
> for another (mesh spoon). Here is a bit of the code:
> 
> #declare t_utensil_WingsMat=texture{
>   #if (use_radiosity<2)
>     #if (BlurredRef)
>       #declare Blurred_Reflection_Samples=10; #declare Blurriness=3;
>       #declare NRand=seed(1);
>       average texture_map{
>         #declare Sample=1; #while (Sample<=Blurred_Reflection_Samples) [ 1
>         pigment{ Gray30 }
>           normal {bozo Blurriness scale .05 translate
> <rand(NRand),rand(NRand),rand(NRand)>*15}
>           finish { reflection .4 }
>         ]
>         #declare Sample=Sample+1; #end
>       }
>     #else pigment {color Gray30} finish {reflection .4} #end
>   #else pigment {color Gray30}
>   #end
> }
> }
> #declare Spoon=object {
>     #include "spoon.inc"
>     spoon
> }
> }
> sphere {y*5,5 texture {t_utensil_WingsMat} translate <-17,80,3>}
> 
> object {Spoon scale 3.5 rotate y*56 translate <12,80,-33>}
> 
> And the spoon object is a wings mesh, looks like this:
> 
> #declare spoon = mesh2 {
> vertex_vectors {1034,...(lots of vectors...)...} normal_vectors
> {1034,...(lots of vectors...)...} texture_list { 1,
>  texture { t_utensil_WingsMat }
> }
> face_indices {2064,...(lots of vectors...)...} normal_indices
> {2064,...(lots of vectors...)...}
> }
> }
> use_radiosity is set to 1.
> 
> So, the sphere renders in about 10 minutes, focal blur and everything. The
> spoon so far has taken 13.5 hours, and it's barely finished with the bowl
> of the spoon. With ordinary reflection the spoon renders very quickly.
> 
> Any ideas? Thanks...
> 
> -Stefan Sittler

Hi everyone,
I wanted to post my RSOCP first (I couldn't find out how to do that with
my Newsreader "Pan"), but I couldn't not answer to this question, because
it's something that interests me a lot. This occurs because the spoon
reflects itself. That means in the worst case with every level of
reflection n, Blurred_Reflection_Samples^n Rays have to be shot. There is
an easy solution to that: Create two copies of your object, one with
no_image and no_shadow and one with no_reflection. The first one gets a
simple reflective texture while the other gets blurred reflection. So,
when the object reflects itself, only one ray is shot for each level after
the first. There is no big slowdown.

Lukas Winter

PS: CPU histograms from scenes with blurred reflection look really
interesting.

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