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

1 files changed, 23 insertions, 5 deletions

diff --git a/source/blender/makesdna/DNA_image_types.h b/source/blender/makesdna/DNA_image_types.h
index 5e4ed16d28e..e975d7acd74 100644
--- a/source/blender/makesdna/DNA_image_types.h
+++ b/source/blender/makesdna/DNA_image_types.h
@@ -56,6 +56,9 @@ typedef struct ImageUser {
   short pass;
   char _pad1[2];
 
+  int tile;
+  int _pad2;
+
   /** Listbase indices, for menu browsing or retrieve buffer. */
   short multi_index, view, layer;
   short flag;
@@ -88,6 +91,19 @@ typedef struct RenderSlot {
   struct RenderResult *render;
 } RenderSlot;
 
+typedef struct ImageTile {
+  struct ImageTile *next, *prev;
+
+  /** Not written in file 2 = TEXTARGET_COUNT. */
+  struct GPUTexture *gputexture[2];
+
+  char ok;
+  char _pad[3];
+
+  int tile_number;
+  char label[64];
+} ImageTile;
+
 /* iuser->flag */
 #define IMA_ANIM_ALWAYS (1 << 0)
 /* #define IMA_UNUSED_1         (1 << 1) */
@@ -109,8 +125,6 @@ typedef struct Image {
 
   /** Not written in file. */
   struct MovieCache *cache;
-  /** Not written in file 2 = TEXTARGET_COUNT. */
-  struct GPUTexture *gputexture[2];
 
   /* sources from: */
   ListBase anims;
@@ -134,8 +148,6 @@ typedef struct Image {
   struct PreviewImage *preview;
 
   int lastused;
-  short ok;
-  char _pad4[6];
 
   /* for generated images */
   int gen_x, gen_y;
@@ -150,12 +162,17 @@ typedef struct Image {
   ColorManagedColorspaceSettings colorspace_settings;
   char alpha_mode;
 
-  char _pad[5];
+  char _pad;
 
   /* Multiview */
   /** For viewer node stereoscopy. */
   char eye;
   char views_format;
+
+  /* ImageTile list for UDIMs. */
+  int active_tile_index;
+  ListBase tiles;
+
   /** ImageView. */
   ListBase views;
   struct Stereo3dFormat *stereo3d_format;
@@ -202,6 +219,7 @@ enum {
   IMA_SRC_MOVIE = 3,
   IMA_SRC_GENERATED = 4,
   IMA_SRC_VIEWER = 5,
+  IMA_SRC_TILED = 6,
 };
 
 /* Image.type, how to handle or generate the image */