Add support for tiled images and the UDIM naming scheme

This patch contains the work that I did during my week at the Code Quest - adding support for tiled images to Blender.

With this patch, images now contain a list of tiles. By default, this just contains one tile, but if the source type is set to Tiled, the user can add additional tiles. When acquiring an ImBuf, the tile to be loaded is specified in the ImageUser.
Therefore, code that is not yet aware of tiles will just access the default tile as usual.

The filenames of the additional tiles are derived from the original filename according to the UDIM naming scheme - the filename contains an index that is calculated as (1001 + 10*<y coordinate of the tile> + <x coordinate of the tile>), where the x coordinate never goes above 9.
Internally, the various tiles are stored in a cache just like sequences. When acquired for the first time, the code will try to load the corresponding file from disk. Alternatively, a new operator can be used to initialize the tile similar to the New Image operator.

The following features are supported so far:
- Automatic detection and loading of all tiles when opening the first tile (1001)
- Saving all tiles
- Adding and removing tiles
- Filling tiles with generated images
- Drawing all tiles in the Image Editor
- Viewing a tiled grid even if no image is selected
- Rendering tiled images in Eevee
- Rendering tiled images in Cycles (in SVM mode)
- Automatically skipping loading of unused tiles in Cycles
- 2D texture painting (also across tiles)
- 3D texture painting (also across tiles, only limitation: individual faces can not cross tile borders)
- Assigning custom labels to individual tiles (drawn in the Image Editor instead of the ID)
- Different resolutions between tiles

There still are some missing features that will be added later (see T72390):
- Workbench engine support
- Packing/Unpacking support
- Baking support
- Cycles OSL support
- many other Blender features that rely on images

Thanks to Brecht for the review and to all who tested the intermediate versions!

Differential Revision: https://developer.blender.org/D3509

3 files changed, 18 insertions, 6 deletions

diff --git a/source/blender/editors/include/ED_image.h b/source/blender/editors/include/ED_image.h
index 69742af9f50..e6d8684a8b2 100644
--- a/source/blender/editors/include/ED_image.h
+++ b/source/blender/editors/include/ED_image.h
@@ -50,7 +50,7 @@ bool ED_space_image_color_sample(struct SpaceImage *sima,
                                  struct ARegion *ar,
                                  int mval[2],
                                  float r_col[3]);
-struct ImBuf *ED_space_image_acquire_buffer(struct SpaceImage *sima, void **r_lock);
+struct ImBuf *ED_space_image_acquire_buffer(struct SpaceImage *sima, void **r_lock, int tile);
 void ED_space_image_release_buffer(struct SpaceImage *sima, struct ImBuf *ibuf, void *lock);
 bool ED_space_image_has_buffer(struct SpaceImage *sima);
 
diff --git a/source/blender/editors/include/ED_paint.h b/source/blender/editors/include/ED_paint.h
index fec4beea809..e15e4c45c4a 100644
--- a/source/blender/editors/include/ED_paint.h
+++ b/source/blender/editors/include/ED_paint.h
@@ -36,15 +36,25 @@ void ED_keymap_paint(struct wmKeyConfig *keyconf);
 
 /* paint_image.c */
 void ED_imapaint_clear_partial_redraw(void);
-void ED_imapaint_dirty_region(
-    struct Image *ima, struct ImBuf *ibuf, int x, int y, int w, int h, bool find_old);
-void ED_imapaint_bucket_fill(struct bContext *C, float color[3], struct wmOperator *op);
+void ED_imapaint_dirty_region(struct Image *ima,
+                              struct ImBuf *ibuf,
+                              int tile_number,
+                              int x,
+                              int y,
+                              int w,
+                              int h,
+                              bool find_old);
+void ED_imapaint_bucket_fill(struct bContext *C,
+                             float color[3],
+                             struct wmOperator *op,
+                             const int mouse[2]);
 
 /* image_undo.c */
 void ED_image_undo_push_begin(const char *name, int paint_mode);
 void ED_image_undo_push_begin_with_image(const char *name,
                                          struct Image *image,
-                                         struct ImBuf *ibuf);
+                                         struct ImBuf *ibuf,
+                                         int tile_number);
 
 void ED_image_undo_push_end(void);
 void ED_image_undo_restore(struct UndoStep *us);
@@ -54,6 +64,7 @@ void ED_image_undosys_type(struct UndoType *ut);
 void *ED_image_paint_tile_find(struct ListBase *undo_tiles,
                                struct Image *ima,
                                struct ImBuf *ibuf,
+                               int tile_number,
                                int x_tile,
                                int y_tile,
                                unsigned short **r_mask,
@@ -62,6 +73,7 @@ void *ED_image_paint_tile_push(struct ListBase *undo_tiles,
                                struct Image *ima,
                                struct ImBuf *ibuf,
                                struct ImBuf **tmpibuf,
+                               int tile_number,
                                int x_tile,
                                int y_tile,
                                unsigned short **r_mask,
diff --git a/source/blender/editors/include/ED_screen.h b/source/blender/editors/include/ED_screen.h
index 4ca7c8f96ad..6a801fc9928 100644
--- a/source/blender/editors/include/ED_screen.h
+++ b/source/blender/editors/include/ED_screen.h
@@ -120,7 +120,7 @@ void ED_region_info_draw_multiline(ARegion *ar,
 void ED_region_image_metadata_draw(
     int x, int y, struct ImBuf *ibuf, const rctf *frame, float zoomx, float zoomy);
 void ED_region_image_metadata_panel_draw(struct ImBuf *ibuf, struct uiLayout *layout);
-void ED_region_grid_draw(struct ARegion *ar, float zoomx, float zoomy);
+void ED_region_grid_draw(struct ARegion *ar, float zoomx, float zoomy, float x0, float y0);
 float ED_region_blend_alpha(struct ARegion *ar);
 void ED_region_visible_rect_calc(struct ARegion *ar, struct rcti *rect);
 const rcti *ED_region_visible_rect(ARegion *ar);