POV-Ray : Newsgroups : povray.general : mesh camera for UV-mapping output : Re: mesh camera for UV-mapping output Server Time
26 Nov 2022 04:51:16 EST (-0500)
  Re: mesh camera for UV-mapping output  
From: And
Date: 12 Nov 2022 09:25:00
Message: <web.636fab54a8b89d338f2c9d9baa81652d@news.povray.org>
William F Pokorny <ano### [at] anonymousorg> wrote:
> > -----------
> >
> > Has this problem been solved?
>
> I'm not aware of a general solution. I don't generate or use uv maps
> much, but some ideas.
>
> - If you are not using interpolation when reading the image map, suspect
> using it might lesson the seam artifact in your case. Interpolation may
> also introduce seams in other cases I think.
>
> - For simpler shapes using the matching camera type - ie spherical
> camera - to create the map images and then the same image_map mapping
> will be cleaner than mesh based texture baking and uv mapping.
>


> - IIRC, there are some suggested ways to bake map images via meshes
> while doing some AA via different meshes which might help. I've never
> played with the technique outlined. I suspect POV-Ray's inbuilt camera
> ray AA won't be of much help.
>
> - Scaling your uv map image up say 2x/3x in an external program will
> likely mitigate the seams.
>


>
> ---
> I have for a long time wondered how seams in the map image are handled
> in the non POV-Ray cgi game. There images are typically cookie cutter
> sheets for different parts of the uv mapping onto the overall mesh. Maps
> I've played with 'sometimes' have visible seams too which in my
> experience often do create minor artifacts...
>
> When we read an image map we can use (pixel) interpolation - but we
> perhaps should not where image maps used for uv mapping (or for any
> non-continuous mapping such as images for cubic warps). The reason is
> the seams cut off sharply in many uv image maps and any interpolation
> will be looking at adjacent (or wrapped) pixels and not pixel adjacency
> as the image is used in uv mapping on the mesh. This, I think, forces us
> to higher resolution maps than might otherwise be required for smooth
> rendered results.
>
> It is possible with cubic warp mapped images, for example, to create the
> images in a way which looks for and includes the correct adjacent pixels
> at the seams so that smaller, interpolated images can be used while uv
> mapping. I think I posted about some of my experiments - using user
> defined cameras to create such 'interpolate-able' images. Unsure how to
> do this in general. Perhaps there are too some post initial image mesh
> walking AA / smoothing techniques possible, but I'm not aware of
> anything like a canned program though.
>
> Anyhow... Interested.
>
> Bill P.


Thanks for your reply.

I have just tried interpolation, when using 'closest(no interpolation)', or
'linear', or any other option it introduce an artifact line. The seams is narrow
but sharp when using 'closest', a little wider when using interpolation(my
example image using 'linear').


-------------------------------------------------------------

> - What happens if you generate your map image with a higher resolution
> mesh than that to which you map in the actual render? It might be too,
> higher resolution image maps (denser mesh camera), help.
>

> - Have you tried rendering at different output resolutions to see how
> any seams might change? (Rendering large and shrinking a help?)


When I generate a 2048x2048 (higher resolution texture image) then applied,
compared to the 1024x1024(first one of this thread), its artifact seams looks
smaller but still exist.


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