Christoph Hormann wrote:

> Samuel Benge wrote:
> 
>>>
>>> BTW, we're not talking about what _looks_ better but what matches the 
>>> actual surface better. I'm saying this because of the different looks 
>>> of the grainy cylinder. Seems the grain size is in the order of the 
>>> accuracy. 
>>
> 
> No, we are talking about what looks better.


In the end, yes.

> Of course it has to 
> resemble the actual model to look good but even some quite significant 
> difference is acceptable as long as it looks reasonable.
> 
> And what you are referring to as 'grain' is simply the pattern function 
> used. The appearance of the cylinder is completely correct in all 
> versions and does not profit much from the patch (the random differences 
> are mostly due to aliasing).


Even the texturing seems to become chopped up with the [discontinuous] 
surface, but it's not really noticable with low accuracy values.

 
>>
>> I'm curious to see how the code below would look (close up), with the 
>> new patch. The lack of interpolation is very clear, I think:
> 
> 
> That's a good example, i rendered them in larger:
> 
> http://www.tu-bs.de/~y0013390/files/sam_test2o.png
> http://www.tu-bs.de/~y0013390/files/sam_test2i.png
> 
> As clearly visible the patch only interpolates the t value (the distance 
> of the intersection from the camera) it does nothing more!  Therefore 
> most artefacts are still there.


It looks like only part of the problem has been fixed with that 
patch.... like there's still another opportunity for interpolation 
somewhere. Is there a bit of code which specially controls edge calculation?

> Note the black areas are - as assumed 
> previously - mostly caused by the use of the high accuracy values for 
> normal calculation as well.  If i just use 1/10 of the value for the 
> normal they are gone:
> 
> http://www.tu-bs.de/~y0013390/files/sam_test2s.png
> 
> Christoph


The surface still looks 'sliced up' (for lack of better description), 
but yes, the black spots are gone.

I don't know how the isosurface is calculated, so I can't really give 
super-useful input here.... but it's like the backside of the isosurface 
isn't taken into account, so the edges have nothing to 'tie' to, or 
interpolate with... they are just left hanging there. Or maybe they ARE 
interpolated with the backside, and the artifacts just happen to be jagged.

At any rate, thank you for satisfying my curiosity on this, Christoph! I 
think Wolfgang's patch is still a step forward, but not quite a step all 
the way towards making isosurfaces useful with high accuracy values.

-Sam

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