Hello Zuegs,

I'm not actually answering your question here, but I'm hoping that if I can 
clarify the problem then someone with more knowledge than me may step in and 
comment.

I've had a look at your code and rendered it with various alternative bozo 
settings.
I've looked at your description of the problem and when you say:
>
> When I set bozo to high value as 50 then reflection should come
> very blurry and should look similar to radiosity-effect. But in
> POV-Ray, reflection on high bump_sized normals looks more
> shinny than blurry...
>
I think you mean that as you pass from bozo 0 to bozo 5 the reflected edges 
of your box become progressively more blurred. As you pass from bozo 5 up to 
bozo 50, you get a greater distribution of reflected light across the 
reflecting surface, but the reflected edges of your box start to become well 
defined again, until you get really quite crisp and distinctive reflections 
of the edges of the box.

I've increased the scale of the finish and zoomed in on a portion of the 
reflection to illustrate this effect. I've also added a little blue sphere 
where the edge of the box meets the surface, so everything below the blue 
dot is a reflection of the box above the blue dot.

camera {
  location <0, 2, -10>
  look_at <1,0,-1>
  angle 15
}
plane { y, 0
  finish { reflection 1.0 ambient 0.0 diffuse 0.0 specular 0.0 }
  normal { bozo 15  scale 0.3 }
}

box { <-1, 0, -1>, <1, 5, 1>
  pigment { color rgb <1, 1, 0> }
  finish { ambient 1.0 diffuse 0.0 specular 0.0 reflection 0.0 }
}
sphere {<1,0,-1>,0.02 pigment {color <0,1,1>} finish {ambient 1.0}}


If you reduce this to bozo 3, you get little or no straight edges to the 
reflected image, whereas above bozo 3 you get progressively more straight 
edge to the reflection. This is what I think you're referring to in your 
second note where you say:
>
> The programmer decided to reflect incomming ray on
> non-disturbed surface what creates the fully mirror effect.
>
I don't fully follow the POV-Ray source code you included in your second 
note, but it seems to me that, if the ray strikes the surface where the bozo 
normal is close to perpendicular to the actual surface, but leaning more 
towards the camera than the box, that the code treats it as if it is exactly 
perpendicular and therefore produces a 'flat' reflection, rather than 
perform the 'real' calculation of the shape of the reflection. Whereas if 
it's close to vertical but leaning more towards the box, it performs a more 
detailed calculation, resulting in no straight edge.

When the bozo setting is relatively low, this approximation is fine and as 
it increases, the approximation becomes more apparent.

Did I correctly describe the effect you're having problems with?

Regards,
Chris B.

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