Just of curiosity: Is there any benefit of the "big normals" approach at blurred
reflections over the "micronormals" approach?

After all, the micronormals approach has the benefit of working in a single pass
if antialiasing or focal blur is used, and as it seems it's also better suited
to be mixed with standard bump mapping (let alone that it is the more "natural"
approach at blurred reflections) - so what does the "big normals" approach offer
to make up for this?

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> Just of curiosity: Is there any benefit of the "big normals" approach at
> blurred reflections over the "micronormals" approach?
> 
> After all, the micronormals approach has the benefit of working in a
> single pass if antialiasing or focal blur is used, and as it seems it's
> also better suited to be mixed with standard bump mapping (let alone that
> it is the more "natural" approach at blurred reflections) - so what does
> the "big normals" approach offer to make up for this?
> 

   Well, the micronormals trick usually needs insane aa settings to not look
grainy, while the macronormals one almost doesn't needs aa. In general, the
macronormals trick is faster for the same apparent smoothness, and doesn't
needs adjustments depending on the image resolution. But you are right about
micronormals being more "natural": they give apparently more accurate
results if you have enough patience.

--
Jaime

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clipka <nomail@nomail> wrote:
> Just of curiosity: Is there any benefit of the "big normals" approach at blurred
> reflections over the "micronormals" approach?

  The micronormals tend to produce a grainy result even with lots of
samples. OTOH antialiasing usually makes the result better (rather
obviously, as more samples will be taken per pixel).

  Macronormals tend to produce good-looking result with less samples,
at least if the amount of blurring is not large. If you need just a little
bit of blurring, macronormals will often be a better choice with respect
to rendering times.
  OTOH if the amount of blurring is large, or sometimes also in other
situations, macronormals can produce visible and ugly banding. This is
not helped by antialiasing.

  So it's always a compromise either way.

-- 
                                                          - Warp

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"clipka" <nomail@nomail> wrote:
> Just of curiosity: Is there any benefit of the "big normals" approach at blurred
> reflections over the "micronormals" approach?

Pardon my ignorance, but what is the "big normals" approach?

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Cousin Ricky <ric### [at] yahoocom> wrote:
> "clipka" <nomail@nomail> wrote:
> > Just of curiosity: Is there any benefit of the "big normals" approach at blurred
> > reflections over the "micronormals" approach?

> Pardon my ignorance, but what is the "big normals" approach?

http://tag.povray.org/povQandT/languageQandT.html#blurredreflection

-- 
                                                          - Warp

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"Cousin Ricky" <ric### [at] yahoocom> wrote:
> "clipka" <nomail@nomail> wrote:
> > Just of curiosity: Is there any benefit of the "big normals" approach at blurred
> > reflections over the "micronormals" approach?
>
> Pardon my ignorance, but what is the "big normals" approach?

To generate blurred reflections or refractions with standard POV, the most
common approach is to define *some* normal pertubation on the surface, and make
sure POV renders each pixel multiple times with differently pertubed normal,
averaging the results.

The "micronormals" approach uses a very fine-grained bump map for this purpose -
smaller than a pixel in size. Rendering such a scene with strong anti-aliasing
automatically causes POV to sample each pixel multple times and also take care
of the averaging, with the slight offsets in the ray resulting in different
pertubation.

The "big normals" approach instead uses very large-scale bump maps - e.g. larger
than the whole picture. Multiple sampling is achieved by rendering the shot
multiple times, while the variations in pertubation are generated by
translating the bump map by a (large) random offset. Averaging is done in a
post-processing step.

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clipka <nomail@nomail> wrote:
> The "big normals" approach instead uses very large-scale bump maps - e.g. larger
> than the whole picture. Multiple sampling is achieved by rendering the shot
> multiple times, while the variations in pertubation are generated by
> translating the bump map by a (large) random offset. Averaging is done in a
> post-processing step.

  I think you should read this:

http://tag.povray.org/povQandT/languageQandT.html#blurredreflection

-- 
                                                          - Warp

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Warp <war### [at] tagpovrayorg> wrote:
> clipka <nomail@nomail> wrote:
> > The "big normals" approach instead uses very large-scale bump maps - e.g. larger
> > than the whole picture. Multiple sampling is achieved by rendering the shot
> > multiple times, while the variations in pertubation are generated by
> > translating the bump map by a (large) random offset. Averaging is done in a
> > post-processing step.
>
>   I think you should read this:
>
> http://tag.povray.org/povQandT/languageQandT.html#blurredreflection

Did already a while ago.

The averaged textures approach didn't stick though. Maybe because it's *fatal*
if you have a lot of reflecting surfaces: The rays POV needs to trace will
explode exponentially with each reflection.

In contrast, if you do the averaging via multiple renders + post-processing, the
number of rays is only increased by a constant factor; at each reflection, the
number of rays multiplies only by the same amount as if the scene used sharp
reflections.

If you let adaptive Anti-aliasing do the job, you still can go with a relatively
low number of rays per pixel in areas that don't have blurred reflective
surfaces. Let alone that you'll usually use Anti-aliasing (or focal blur) for a
final shot anyway.

After the first blurred reflection, there's actually not much benefit in
multiplying the number of rays even more.

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Cousin Ricky nous illumina en ce 2009-03-12 08:13 -->
> "clipka" <nomail@nomail> wrote:
>> Just of curiosity: Is there any benefit of the "big normals" approach at blurred
>> reflections over the "micronormals" approach?
> 
> Pardon my ignorance, but what is the "big normals" approach?
> 
> 

The "big normals" is done by averaging several normals that are scaled to a 
lagre value. Each averaged normal pattern is randomly translated by an egualy 
large value. A typical scale and translations is around 1000 to 1000000.
Benefit: don't need antialiasing. Often give beter results without antialiasing.
But: Often requires the averaging of more normals, often the alowed maximum of 
255 in a normal_map.

The micronormal use an average of normal patterns scaled very small and 
translated by a tiny random value. A typical scale and translate is around 0.001 
or smaller.
Benefit: usualy require the averaging of only a few normals, in some cases, only 
one normal can be used.
But: Work beter when using at least some antialiasing or the image can looks to 
grainy.

-- 
Alain
-------------------------------------------------
Don't waste your time on a man/woman, who isn't willing to waste their time on you.

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clipka nous illumina en ce 2009-03-12 14:24 -->
> Warp <war### [at] tagpovrayorg> wrote:
>> clipka <nomail@nomail> wrote:
>>> The "big normals" approach instead uses very large-scale bump maps - e.g. larger
>>> than the whole picture. Multiple sampling is achieved by rendering the shot
>>> multiple times, while the variations in pertubation are generated by
>>> translating the bump map by a (large) random offset. Averaging is done in a
>>> post-processing step.
>>   I think you should read this:
>>
>> http://tag.povray.org/povQandT/languageQandT.html#blurredreflection
> 
> Did already a while ago.
> 
> The averaged textures approach didn't stick though. Maybe because it's *fatal*
> if you have a lot of reflecting surfaces: The rays POV needs to trace will
> explode exponentially with each reflection.
> 
> In contrast, if you do the averaging via multiple renders + post-processing, the
> number of rays is only increased by a constant factor; at each reflection, the
> number of rays multiplies only by the same amount as if the scene used sharp
> reflections.
> 
> If you let adaptive Anti-aliasing do the job, you still can go with a relatively
> low number of rays per pixel in areas that don't have blurred reflective
> surfaces. Let alone that you'll usually use Anti-aliasing (or focal blur) for a
> final shot anyway.
> 
> After the first blurred reflection, there's actually not much benefit in
> multiplying the number of rays even more.
> 
> 
> 
A work around for that problem:
For the objects that have blured reflection, make two copies.
The first one will have the blured reflection AND the no_reflection attribute.
The second will only have normal relfection AND no_image.

That way, the object with blured reflection will not show in the reflections, 
but the one with no_image will.

-- 
Alain
-------------------------------------------------
Congregationalist: Shit that happens to one person is just as good as shit that 
happens to another.

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