2 files changed, 24 insertions, 29 deletions

diff --git a/source/blender/blenkernel/intern/material.c b/source/blender/blenkernel/intern/material.c
index 59530a6d6a6..796ed4f8316 100644
--- a/source/blender/blenkernel/intern/material.c
+++ b/source/blender/blenkernel/intern/material.c
@@ -653,38 +653,29 @@ Material **BKE_object_material_get_p(Object *ob, short act)
 
   /* if object cannot have material, (totcolp == NULL) */
   totcolp = BKE_object_material_len_p(ob);
-  if (totcolp == NULL || ob->totcol == 0) {
+  if (totcolp == NULL || *totcolp == 0) {
     return NULL;
   }
 
-  /* return NULL for invalid 'act', can happen for mesh face indices */
-  if (act > ob->totcol) {
-    return NULL;
-  }
-  if (act <= 0) {
-    if (act < 0) {
-      CLOG_ERROR(&LOG, "Negative material index!");
-    }
-    return NULL;
-  }
+  /* Clamp to number of slots if index is out of range, same convention as used for rendering. */
+  const int slot_index = clamp_i(act - 1, 0, *totcolp - 1);
 
-  if (ob->matbits && ob->matbits[act - 1]) { /* in object */
-    ma_p = &ob->mat[act - 1];
+  /* Fix inconsistency which may happen when library linked data reduces the number of
+   * slots but object was not updated. Ideally should be fixed elsewhere. */
+  if (*totcolp < ob->totcol) {
+    ob->totcol = *totcolp;
   }
-  else { /* in data */
-
-    /* check for inconsistency */
-    if (*totcolp < ob->totcol) {
-      ob->totcol = *totcolp;
-    }
-    if (act > ob->totcol) {
-      act = ob->totcol;
-    }
 
+  if (slot_index < ob->totcol && ob->matbits && ob->matbits[slot_index]) {
+    /* Use object material slot. */
+    ma_p = &ob->mat[slot_index];
+  }
+  else {
+    /* Use data material slot. */
     matarar = BKE_object_material_array_p(ob);
 
     if (matarar && *matarar) {
-      ma_p = &(*matarar)[act - 1];
+      ma_p = &(*matarar)[slot_index];
     }
     else {
       ma_p = NULL;
@@ -717,17 +708,17 @@ static ID *get_evaluated_object_data_with_materials(Object *ob)
 Material *BKE_object_material_get_eval(Object *ob, short act)
 {
   BLI_assert(DEG_is_evaluated_object(ob));
-  const int slot_index = act - 1;
 
-  if (slot_index < 0) {
-    return NULL;
-  }
   ID *data = get_evaluated_object_data_with_materials(ob);
   const short *tot_slots_data_ptr = BKE_id_material_len_p(data);
   const int tot_slots_data = tot_slots_data_ptr ? *tot_slots_data_ptr : 0;
-  if (slot_index >= tot_slots_data) {
+
+  if (tot_slots_data == 0) {
     return NULL;
   }
+
+  /* Clamp to number of slots if index is out of range, same convention as used for rendering. */
+  const int slot_index = clamp_i(act - 1, 0, tot_slots_data - 1);
   const int tot_slots_object = ob->totcol;
 
   Material ***materials_data_ptr = BKE_id_material_array_p(data);
diff --git a/source/blender/render/intern/bake.c b/source/blender/render/intern/bake.c
index 9b56e18bb26..d9f7f9fa0af 100644
--- a/source/blender/render/intern/bake.c
+++ b/source/blender/render/intern/bake.c
@@ -747,6 +747,7 @@ void RE_bake_pixels_populate(Mesh *me,
   BKE_mesh_recalc_looptri(loops, polys, verts, me->totloop, me->totpoly, looptri);
 
   const int *material_indices = BKE_mesh_material_indices(me);
+  const int materials_num = targets->materials_num;
 
   for (int i = 0; i < tottri; i++) {
     const MLoopTri *lt = &looptri[i];
@@ -754,7 +755,10 @@ void RE_bake_pixels_populate(Mesh *me,
     bd.primitive_id = i;
 
     /* Find images matching this material. */
-    Image *image = targets->material_to_image[material_indices ? material_indices[lt->poly] : 0];
+    const int material_index = (material_indices && materials_num) ?
+                                   clamp_i(material_indices[lt->poly], 0, materials_num - 1) :
+                                   0;
+    Image *image = targets->material_to_image[material_index];
     for (int image_id = 0; image_id < targets->images_num; image_id++) {
       BakeImage *bk_image = &targets->images[image_id];
       if (bk_image->image != image) {