I have a quesion about setting the max gradient option in POV-Ray 3.5
beta. If I move the camera or the isosurface between renders (without
changing the function of the isosurface) do I need to reevaluate the max gradient?

I am using two isosurfaces and evaluate gave me max gradients of 1.323
and 1.019.

In a related matter: Does the render size effect the gradient? the docs
imply that it doesn't. I guess what I really don't understand is what
the max_gradient is. 

Josh English
eng### [at] spiritonecom

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I don't know the answer, but in one scene I had an isosurface repeated 4
times and I got at least (I don't remember exactly) 3 different
max_gradients. Read what you want from that.

--
Jonathan.

"Josh English" <eng### [at] spiritonecom> ha scritto nel messaggio
news:3BF423E7.7908940E@spiritone.com...
> I have a quesion about setting the max gradient option in POV-Ray 3.5
> beta. If I move the camera or the isosurface between renders (without
> changing the function of the isosurface) do I need to reevaluate the max
gradient?
>
> I am using two isosurfaces and evaluate gave me max gradients of 1.323
> and 1.019.
>
> In a related matter: Does the render size effect the gradient? the docs
> imply that it doesn't. I guess what I really don't understand is what
> the max_gradient is.
>
> Josh English
> eng### [at] spiritonecom

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Josh English wrote:
> 
> I have a quesion about setting the max gradient option in POV-Ray 3.5
> beta. If I move the camera or the isosurface between renders (without
> changing the function of the isosurface) do I need to reevaluate the max gradient?
> 
> I am using two isosurfaces and evaluate gave me max gradients of 1.323
> and 1.019.

The maximum gradient is a property of the function so it's always the same
no matter what you do.  But when you use 'evaluate' Povray tries to find
out the maximum gradient and it can come to different or even wrong
results with different situations.  Another thing is that you don't always
need a max_gradient value as high as the true maximum gradient when it
only occurs at places not relevant for finding the intersection.

> In a related matter: Does the render size effect the gradient? the docs
> imply that it doesn't. I guess what I really don't understand is what
> the max_gradient is.
> 

Again it does not influence the true maximum gradient, but holes or
artefacts not occuring in a small size render can become visible at larger
sizes.  Also when you decrease the accuracy value for the larger render
and the function has a strong small scale structure it will usually
require a higher max_gradient.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

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