Like the fool that I am I had rendered without making any change to the
scale.  I was quickly doing a copy&paste then render without looking first
so I thought you were "crying wolf".
I think it could easily be said to be a bug.  Not a error type thing though
but just a disfunctional sort.  I agree very much that it should scale in a
uniform manner and not switch around like that.  Guess it could be argued it
isn't a flaw but I can't see textures operating correctly as is currently.

Bob

Rune S. Johansen <run### [at] inamecom> wrote in message
news:37fe6bf3@news.povray.org...
> /*
> I keep being confused by these normals!
>
> I consider it a bug that the depth of a normal
> doesn't always proportionally follow the scaling
> affecting the normal.
>
> I think the problem is quite serious. Again and
> again I find myself unable to work effectively
> with normals because the way they work (regarding
> scaling) just isn't logic but on the contrary
> strange and very inconvenient!
>
> If you consider it a bug too I think it should be
> fixed.
>
> I know it would break a whole lot of scenes, but
> wouldn't it be possible to make some kind of
> switch so the user could switch between the old
> wrong method and a new proper one? Maybe the
> already existing #version switch could be used
> for that?
>
> Below the problem is described in details.
>
> Please note that I've found out more about the
> problem since my last posts regarding normals so
> I'm not just saying exactly the same again...! :-)
>
> There are four basic types of normals:
>
> o Block pattern normals (checker, hexagon, brick).
> o Bump maps.
> o Specialized normals (bumps, dents, ripples,
>   waves, wrinkles).
> o The rest is continuous pattern normals.
>
> When working with normals you can modify both the
> scale of the pattern and the depth of the pattern.
>
> When you apply a *specialized normal* to an object
> and afterwards scale the object smaller or larger,
> the depth of the normal pattern follows the scale
> of the pattern proportionally as you would expect.
>
> However, when you apply a *continuous pattern
> normal* to an object and scale the object smaller
> or larger afterwards, the depth of the normal
> pattern *doesn't* follow the scale of the pattern.
> That is, if you scale the object smaller the
> normal seems to be too deep and if you scale the
> object larger the normal seems to be too flat.
>
> If you want to have the depth of a *continuous
> pattern normal* to follow the scale of the pattern
> proportionally you must multiply the depth of the
> normal pattern with the same amount you scale the
> object with. However, for some reason that only
> works when scaling the object larger, not when
> scaling it smaller.
>
> Just to confuse you even more: If you have an
> *continuous pattern normal* inside a *normal_map*
> it works as if it were a *specialized normal*,
> that is, the depth of the normal pattern follows
> the scale of the pattern proportionally. That's
> what I just found out and that makes it all even
> more confusing and inconvenient!
>
> Here's an example of it all:
>
> Left spheres:  Normal depth of 1.
> Right spheres: Normal depth proportional to "Scale".
> Upper spheres: A plain crackle normal.
> Lower spheres: Same normal but inside a normal_map.
>
> Change "Scale" to other values to see the effects.
> */
>
> #declare Scale=1;
>
> camera{location -8*z look_at 0 orthographic  scale Scale}
> light_source{<1,1,-1>*100,color 1 shadowless scale Scale}
> #default{pigment{color rgb 1}}
>
> #declare N1a=normal{crackle 1    }
> #declare N1b=normal{crackle Scale}
>
> #declare N2a=normal{bozo normal_map{[0 N1a][1 N1a]}}
> #declare N2b=normal{bozo normal_map{[0 N1b][1 N1b]}}
>
> sphere{0,2 normal{N1a}translate <-2,+2,> scale Scale}
> sphere{0,2 normal{N1b}translate <+2,+2,> scale Scale}
> sphere{0,2 normal{N2a}translate <-2,-2,> scale Scale}
> sphere{0,2 normal{N2b}translate <+2,-2,> scale Scale}
>
>
>
>
>

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