On 2/13/25 22:06, William F Pokorny wrote:
> With respect to bump_map{}, the first root issue is due the multiple 
> samples sometimes spanning the seam in a given mapping type. The second 
> root issue - sitting smack on top of the first - is that games are being 
> played internal to all interpolations which introduce / mangle the 
> values in the pixels at the images edges.

So, what I decided to fix and not... (R19 v0.6.13.0 of yuqk fork)

The current collection of fixes has been implemented against the 
bump_map{} feature alone. The issues are most apparent / vibrant with 
this feature.

Within the bump_map{} code the planar (0) and angular (7) map types have 
been left as is code wise. (spherical, cylindrical, toroidal were updated)

The planar map because the user can use scaling / placements to avoid 
problem seams if they show up & the artefacts tend to be much less 
noticeable with planar mapping.

With the angular mapping usage any issues are both unlikely to show up 
and unlikely to matter if they do.

Ultimately there are no perfect solutions here. At the image edges we 
end up with a pile of trade-offs and no, general, ideal solutions.

Attached are two images.

--

The first is the zoomed in on the sphere surface form shown in the prior 
post. It basically shows things are better.

Results are solid for no interpolation so long as the image pixel 
resolution is >> effective pixel use in the rendered image.

Results are good for the bi-linear interpolation, but due the fix we've 
traded a small flat region at the image's pixel value over generated, 
additional edge values.

Results for the bi-cubic interpolation are accurate, but this means we 
now often see the ringing below 0.0 and above 1.0 which happens with 
this interpolation type.

Results for the normalized-distance are much better, but more visible 
than bi-linear.

---

The second image showing comparisons. Top row no interpolation needing 
only the fix for the first issue. The rows two through four show the 
interpolations 2,3 and 4 with the first issue fix in place. The center 
column shows the interpolation type specific fixes for each. The right 
column showing differences.

Bill P.

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Attachments:
Download 'bump_map_updates.png' (104 KB) Download 'bump_map_withfixes.png' (14 KB)

Preview of image 'bump_map_updates.png'

Preview of image 'bump_map_withfixes.png'