POV-Ray : Newsgroups : povray.binaries.animations : Mysterious vanishing isosurface : Re: Mysterious vanishing isosurface Server Time
16 May 2022 20:40:50 EDT (-0400)
  Re: Mysterious vanishing isosurface  
From: clipka
Date: 9 Dec 2016 00:22:15
Message: <584a3f87$1@news.povray.org>
Am 09.12.2016 um 06:09 schrieb Mike Horvath:
> On 12/9/2016 12:02 AM, clipka wrote:
>> Am 09.12.2016 um 03:36 schrieb Mike Horvath:
>>> If I rotate the camera 90 degrees around the x axis, the isosurface
>>> disappears.
>>
>> My guess would be that on the "bottom" side of the shape, the function
>> has a much stronger gradient, so that when POV-Ray starts searching the
>> contained_by volume for intersection points starting from that side, it
>> finds incredibly huge values and thinks, "oh, I must still be VERY far
>> from the surface" -- advances a good deal, _skipping_ over the actual
>> body of the shape, and finds itself still outside, concluding that there
>> is no shape at all.
>>
>> You must either increase max_gradient to fit even that portion of the
>> shape, or somehow find a way to get a nicer gradient down there.
>>
> 
> Is there any "adaptive" form of max_gradient, so the setting is only
> high where needed?

There's that `evaluate` mechanism; but I have no idea how it even works.


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