[Bf-committers] [Bf-blender-cvs] SVN commit: /data/svn/bf-blender [49633] trunk/blender/source/blender: Switching images in the image space would modify UV coordinates.

[Campbell Barton]

Hi Antony,

The ability to keep aspect while changing images would be nice as an option,
but this was causing problems for artists here where you often paint
at resolutions like 1024x1024, but use photos as a reference.
(in this case painting onto a 4096x4096 texture, using footage from
film as a clone layer).

When Sebastian was switching reference images it was modifying UV's -
a problem with this is it always shrinks the UV's - so we would end up
with very squashed UV's.

This is tricky to do nicely for a few reasons.
- Texface data is mostly deprecated - in that for rendering in blender
and cycles its not a common work-flow any more - even in the game
engine GLSL is common enough now.
... from my observations TexFace images are mainly used as a kind of -
what-image-was-I-last-working-on cache, and for baking and painting
since both need a way to target a single texture. But otherwise they
are not used so much anymore for actual texturing.

- Since BMesh these are internally separate data layers, even though
they are exposed as one, The ability to have UV's but not TexFace
would be nice and save some memory since often artists only want the
UV's - this is one of the reasons Im not a fan of storing the aspect
setting per face, the other reason is its not really in user control -
if they by accident have one face with the wrong aspect setting -
fixing is a matter of second-guessing what blender internal code does,
or even reading code to see whats going on - Id prefer options which
have a big impact on how tools behave be more transparent to the user.

----

Here are some suggestions for how to implement these features,
interested to know what others think.

Re: Aspect Correction on image switching
Having the UV aspect maintained while switching images could be a
scene toolsetting, though we don't have a really good place in the UI,
for now the image menu - next to `Snap to Pixels`.
... Im still not so happy that the UVs always shrink but thats really
a separate issue.


Re: Unwrap aspect correction
The UV aspect correction while unwrapping is more tricky since you may
well have some parts of a mesh that are aspect corrected and some
not...
The best option I can see here is to store the setting per image ---
failing this per UV layer or material,
if we fully deprecate TexFace some day a material will still reference
images - so the active image can be found a different way but its
aspect still used so IMHO this is future proof, this will be needed
for baking and painting too.

Rather then adding a preserve aspect option, we could use the existing
x/y-aspect in the image settings to do aspect correction for
unwrapping. This way the user will see the correct aspect in the view
too.


On Mon, Aug 6, 2012 at 10:17 PM, Antony Riakiotakis <kalast at gmail.com> wrote:
> Hi, I agree that it shouldn't behave differently depending on the engine.
> Probably storing the property per face is a bad decision, however I think
> that changing images should somehow at least expose an option to do aspect
> correction. This patch was written to address bug #31962
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-- 
- Campbell