UDIM: Support virtual filenames

This implements the design detailed in T92696 to support virtual
filenames for UDIM textures. Currently, the following 2 substitution
tokens are supported:

| Token | Meaning |
| ----- | ---- |
| <UDIM>   | 1001 + u-tile + v-tile * 10 |
| <UVTILE> | Equivalent to u<u-tile + 1>_v<v-tile + 1> |

Example for u-tile of 3 and v-tile of 1:
filename.<UDIM>_ver0023.png   --> filename.1014_ver0023.png
filename.<UVTILE>_ver0023.png --> filename.u4_v2_ver0023.png

For image loading, the existing workflow is unchanged. A user can select
one or more image files, belonging to one or more UDIM tile sets, and
have Blender load them all as it does today. Now the <UVTILE> format is
"guessed" just as the <UDIM> format was guessed before.

If guessing fails, the user can simply go into the Image Editor and type
the proper substitution in the filename. Once typing is complete,
Blender will reload the files and correctly fill the tiles. This
workflow is new as attempting to fix the guessing in current versions
did not really work, and the user was often stuck with a confusing
situation.

For image saving, the existing workflow is changed slightly. Currently,
when saving, a user has to be sure to type the filename of the first
tile (e.g. filename.1001.png) to save the entire UDIM set. The number
could differ if they start at a different tile etc. This is confusing.
Now, the user should type a filename containing the appropriate
substitution token. By default Blender will fill in a default name using
the <UDIM> token but the user is free to save out images using <UVTILE>
if they wish.

Differential Revision: https://developer.blender.org/D13057

1 files changed, 2 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_bpath.h b/source/blender/blenkernel/BKE_bpath.h
index bae151f6a72..bc9e3f01e96 100644
--- a/source/blender/blenkernel/BKE_bpath.h
+++ b/source/blender/blenkernel/BKE_bpath.h
@@ -49,6 +49,8 @@ typedef enum eBPathForeachFlag {
   BKE_BPATH_FOREACH_PATH_SKIP_LINKED = (1 << 1),
   /** Skip paths when their matching data is packed. */
   BKE_BPATH_FOREACH_PATH_SKIP_PACKED = (1 << 2),
+  /** Resolve tokens within a virtual filepath to a single, concrete, filepath. */
+  BKE_BPATH_FOREACH_PATH_RESOLVE_TOKEN = (1 << 3),
   /* Skip weak reference paths. Those paths are typically 'nice to have' extra information, but are
    * not used as actual source of data by the current .blend file.
    *