Am 02.01.2019 um 08:18 schrieb COMPATT:
> Even when I use an accuracy of 0.0001 I continue to get moire patterns at the
> "terminator" of my planet when the light rays would be striking at a very low
> angle to the isosurface I am not getting a max gradient error but I am using a
> very high resolution greyscale topographic image map any ideas on how to make
> them go away completely? I am not interested in using a mesh instead I would
> like to do this just using the image map as an isosurface function. Not sure
> what to include in this post to help you help me so please let me know what
> other info will be helpful

As Bald Eagle already suggests, you need a much lower accuracy setting.

In isosurfaces, intersection points are not computed in a single step 
using a formula, but rather via a bisection-based iterative algorithm 
that narrows down the location of the intersection point until it is at 
most `accuracy` units off the mathematically correct surface.

Due to how the bisection works, you essentially get "terracing" on your 
isosurface, and the pattern you see are the terrace steps casting shadows.

You need to reduce `accuracy` to a value low enough that the height of 
the terrace steps falls within POV-Ray's precision bounds for shadow 
calculations. 1e-6 will do for the scene you posted.


(The moire pattern is a moire pattern indeed, but in this case does not 
arise from interaction between image content and the pixel structure of 
the image, but from the interaction between the shape and the bisection 
intervals. Not sure how you got anti-aliasing to affect it, but I 
suspect you may have toyed with other settings as well and simply forgot.)

Post a reply to this message