Christoph Hormann wrote:

> My question was if your change makes a difference to the appearance of
> an isosurface despite possible effects on shadow ray tests.  This is
> best to test with high detail surface features of a size similar to the
> accuracy value.
> 
I don't know. But since you are the isosurface expert around here, 
it would be nice if you could have a look at it and run some tests. 

>>>I agree with Thorsten that the interpolation will probably cause
>>>slowdown without much advantage
>>>
>> I am not sure about that. Because the gain in accuracy is considerably.
> 
> Note this is not a real gain in accuracy - it would be if the function
> value changed linearly between the two points but obviously it does not
> in most cases.  A comparitive test with raising accuracy and using your
> technique vs. current technique with low accuracy value would be
> necessary.
> 
It _is_ generally a real gain as long as 
- you use steady functions, i.e. functions with finite gradient which is 
  what you always do and 
- the function does not change very much in scale of accuracy. 

So it is a gain for nearly all real-life scenes. And for such things 
like high micro-details on the surface, it should at least not do 
worse. 

>>[...]
>> should work as well (and does for my scenes). All the other conditions
>> are just to work around conditions which I am not sure about.
> 
> You should at least test with the most common special situations (use in
> CSG, view of the isosurface from inside, high gradient functions etc.).
> 
Could you please?

Wolfgang

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