Bake: add UDIM tile baking support

Works for both Cycles and multires bake. Triangles are baked to multiple
UDIM images if they span across them, though such UV layouts are generally
discouraged as there is no filtering across UDIM tiles.

The bake margin currently only works within UDIM tiles. For the extend method
this is logical, for the adjacent faces method it may be useful to support
copying pixels from other UDIM tiles, though this seems somewhat complicated.

Fixes T95190

Ref T72390

1 files changed, 28 insertions, 21 deletions

diff --git a/source/blender/render/intern/bake.c b/source/blender/render/intern/bake.c
index 69235fb6cb1..5953c0f0f8f 100644
--- a/source/blender/render/intern/bake.c
+++ b/source/blender/render/intern/bake.c
@@ -146,12 +146,13 @@ void RE_bake_margin(ImBuf *ibuf,
                     const int margin,
                     const char margin_type,
                     Mesh const *me,
-                    char const *uv_layer)
+                    char const *uv_layer,
+                    const float uv_offset[2])
 {
   /* margin */
   switch (margin_type) {
     case R_BAKE_ADJACENT_FACES:
-      RE_generate_texturemargin_adjacentfaces(ibuf, mask, margin, me, uv_layer);
+      RE_generate_texturemargin_adjacentfaces(ibuf, mask, margin, me, uv_layer, uv_offset);
       break;
     default:
     /* fall through */
@@ -746,30 +747,36 @@ void RE_bake_pixels_populate(Mesh *me,
   for (int i = 0; i < tottri; i++) {
     const MLoopTri *lt = &looptri[i];
     const MPoly *mp = &me->mpoly[lt->poly];
-    float vec[3][2];
-    int mat_nr = mp->mat_nr;
-    int image_id = targets->material_to_image[mat_nr];
 
-    if (image_id < 0) {
-      continue;
-    }
-
-    bd.bk_image = &targets->images[image_id];
     bd.primitive_id = i;
 
-    for (int a = 0; a < 3; a++) {
-      const float *uv = mloopuv[lt->tri[a]].uv;
+    /* Find images matching this material. */
+    Image *image = targets->material_to_image[mp->mat_nr];
+    for (int image_id = 0; image_id < targets->images_num; image_id++) {
+      BakeImage *bk_image = &targets->images[image_id];
+      if (bk_image->image != image) {
+        continue;
+      }
 
-      /* NOTE(campbell): workaround for pixel aligned UVs which are common and can screw up our
-       * intersection tests where a pixel gets in between 2 faces or the middle of a quad,
-       * camera aligned quads also have this problem but they are less common.
-       * Add a small offset to the UVs, fixes bug T18685. */
-      vec[a][0] = uv[0] * (float)bd.bk_image->width - (0.5f + 0.001f);
-      vec[a][1] = uv[1] * (float)bd.bk_image->height - (0.5f + 0.002f);
-    }
+      /* Compute triangle vertex UV coordinates. */
+      float vec[3][2];
+      for (int a = 0; a < 3; a++) {
+        const float *uv = mloopuv[lt->tri[a]].uv;
+
+        /* NOTE(campbell): workaround for pixel aligned UVs which are common and can screw up our
+         * intersection tests where a pixel gets in between 2 faces or the middle of a quad,
+         * camera aligned quads also have this problem but they are less common.
+         * Add a small offset to the UVs, fixes bug T18685. */
+        vec[a][0] = (uv[0] - bk_image->uv_offset[0]) * (float)bk_image->width - (0.5f + 0.001f);
+        vec[a][1] = (uv[1] - bk_image->uv_offset[1]) * (float)bk_image->height - (0.5f + 0.002f);
+      }
 
-    bake_differentials(&bd, vec[0], vec[1], vec[2]);
-    zspan_scanconvert(&bd.zspan[image_id], (void *)&bd, vec[0], vec[1], vec[2], store_bake_pixel);
+      /* Rasterize triangle. */
+      bd.bk_image = bk_image;
+      bake_differentials(&bd, vec[0], vec[1], vec[2]);
+      zspan_scanconvert(
+          &bd.zspan[image_id], (void *)&bd, vec[0], vec[1], vec[2], store_bake_pixel);
+    }
   }
 
   for (int i = 0; i < targets->images_num; i++) {