fix [#24780] Metaballs are not drawn correctly in new scenes

this is a can of worms, at the moment blender depends on broken behavior for metaballs:
 find_basis_mball() can return a metaball object that fails a is_basis_mball() check which makes this logic very confusing (added note about this in mball.c).

Metaballs needs a refactor however at least make drawing fail consistently,
For wire draw is_basis_mball() wasn't being checked, for solid drawing it was (hence the strange wire frame).

For now the motherball needs to exist in the main scene else it wont work.

source/blender/blenkernel/intern/mball.c

@@ -309,6 +309,19 @@ float *make_orco_mball(Object *ob, ListBase *dispbase)
 
 	return orcodata;
 }
+
+/* Note on mball basis stuff 2.5x (this is a can of worms)
+ * This really needs a rewrite/refactorm its totally broken in anything other then basic cases
+ * Multiple Scenes + Set Scenes & mixing mball basis SHOULD work but fails to update the depsgraph on rename
+ * and linking into scenes or removal of basis mball. so take care when changing this code.
+ * 
+ * Main idiot thing here is that the system returns find_basis_mball() objects which fail a is_basis_mball() test.
+ *
+ * Not only that but the depsgraph and ther areas depend on this behavior!, so making small fixes here isnt worth it.
+ * - campbell
+ */
+
+
 /** \brief Test, if Object *ob is basic MetaBall.
  *
  * It test last character of Object ID name. If last character
@@ -385,6 +398,8 @@ void copy_mball_properties(Scene *scene, Object *active_object)
  * its name. All MetaBalls with same base of name can be
  * blended. MetaBalls with different basic name can't be
  * blended.
+ *
+ * warning!, is_basis_mball() can fail on returned object, see long note above.
  */
 Object *find_basis_mball(Scene *scene, Object *basis)
 {

source/blender/editors/object/object_add.c

@@ -486,16 +486,6 @@ void OBJECT_OT_camera_add(wmOperatorType *ot)
 
 
 /* ***************** add primitives *************** */
-
-static EnumPropertyItem prop_metaball_types[]= {
-	{MB_BALL, "MBALL_BALL", ICON_META_BALL, "Meta Ball", ""},
-	{MB_TUBE, "MBALL_CAPSULE", ICON_META_CAPSULE, "Meta Capsule", ""},
-	{MB_PLANE, "MBALL_PLANE", ICON_META_PLANE, "Meta Plane", ""},
-	{MB_CUBE, "MBALL_CUBE", ICON_META_CUBE, "Meta Cube", ""},
-	{MB_ELIPSOID, "MBALL_ELLIPSOID", ICON_META_ELLIPSOID, "Meta Ellipsoid", ""},
-	{0, NULL, 0, NULL, NULL}
-};
-
 static int object_metaball_add_exec(bContext *C, wmOperator *op)
 {
 	Object *obedit= CTX_data_edit_object(C);
@@ -565,7 +555,7 @@ void OBJECT_OT_metaball_add(wmOperatorType *ot)
 	/* flags */
 	ot->flag= OPTYPE_REGISTER|OPTYPE_UNDO;
 	
-	RNA_def_enum(ot->srna, "type", prop_metaball_types, 0, "Primitive", "");
+	RNA_def_enum(ot->srna, "type", metaelem_type_items, 0, "Primitive", "");
 	ED_object_add_generic_props(ot, TRUE);
 }
 

source/blender/editors/space_view3d/drawobject.c

@@ -5352,10 +5352,12 @@ static void draw_bounding_volume(Scene *scene, Object *ob)
 		bb= ob->bb ? ob->bb : ( (Curve *)ob->data )->bb;
 	}
 	else if(ob->type==OB_MBALL) {
-		bb= ob->bb;
-		if(bb==0) {
-			makeDispListMBall(scene, ob);
+		if(is_basis_mball(ob)) {
 			bb= ob->bb;
+			if(bb==0) {
+				makeDispListMBall(scene, ob);
+				bb= ob->bb;
+			}
 		}
 	}
 	else {
@@ -5435,8 +5437,10 @@ static void drawSolidSelect(Scene *scene, View3D *v3d, ARegion *ar, Base *base)
 			draw_index_wire= 1;
 		}
 	} else if (ob->type==OB_MBALL) {
-		if((base->flag & OB_FROMDUPLI)==0) 
-			drawDispListwire(&ob->disp);
+		if(is_basis_mball(ob)) {
+			if((base->flag & OB_FROMDUPLI)==0)
+				drawDispListwire(&ob->disp);
+		}
 	}
 	else if(ob->type==OB_ARMATURE) {
 		if(!(ob->mode & OB_MODE_POSE))
@@ -5490,7 +5494,9 @@ static void drawWireExtra(Scene *scene, RegionView3D *rv3d, Object *ob)
 				draw_index_wire= 1;
 		}
 	} else if (ob->type==OB_MBALL) {
-		drawDispListwire(&ob->disp);
+		if(is_basis_mball(ob)) {
+			drawDispListwire(&ob->disp);
+		}
 	}
 
 	glDepthMask(1);

source/blender/makesrna/RNA_enum_types.h

@@ -36,6 +36,7 @@ extern EnumPropertyItem DummyRNA_NULL_items[];
 extern EnumPropertyItem DummyRNA_DEFAULT_items[];
 
 extern EnumPropertyItem object_mode_items[];
+extern EnumPropertyItem metaelem_type_items[];
 
 extern EnumPropertyItem proportional_falloff_items[];
 extern EnumPropertyItem proportional_editing_items[];

source/blender/makesrna/intern/rna_meta.c

@@ -25,6 +25,7 @@
 #include <stdlib.h>
 
 #include "RNA_define.h"
+#include "RNA_enum_types.h"
 
 #include "rna_internal.h"
 
@@ -138,14 +139,6 @@ static void rna_MetaBall_elements_remove(MetaBall *mb, ReportList *reports, Meta
 
 #else
 
-static EnumPropertyItem metaelem_type_items[] = {
-	{MB_BALL, "BALL", ICON_META_BALL, "Ball", ""},
-	{MB_TUBE, "CAPSULE", ICON_META_CAPSULE, "Capsule", ""},
-	{MB_PLANE, "PLANE", ICON_META_PLANE, "Plane", ""},
-	{MB_ELIPSOID, "ELLIPSOID", ICON_META_ELLIPSOID, "Ellipsoid", ""}, // NOTE: typo at original definition!
-	{MB_CUBE, "CUBE", ICON_META_CUBE, "Cube", ""},
-	{0, NULL, 0, NULL, NULL}};
-
 static void rna_def_metaelement(BlenderRNA *brna)
 {
 	StructRNA *srna;
@@ -155,7 +148,7 @@ static void rna_def_metaelement(BlenderRNA *brna)
 	RNA_def_struct_sdna(srna, "MetaElem");
 	RNA_def_struct_ui_text(srna, "Meta Element", "Blobby element in a MetaBall datablock");
 	RNA_def_struct_ui_icon(srna, ICON_OUTLINER_DATA_META);
-	
+
 	/* enums */
 	prop= RNA_def_property(srna, "type", PROP_ENUM, PROP_NONE);
 	RNA_def_property_enum_items(prop, metaelem_type_items);

source/blender/makesrna/intern/rna_object.c

@@ -40,6 +40,7 @@
 #include "DNA_object_types.h"
 #include "DNA_property_types.h"
 #include "DNA_scene_types.h"
+#include "DNA_meta_types.h"
 
 #include "BLO_sys_types.h" /* needed for intptr_t used in ED_mesh.h */
 #include "ED_mesh.h"
@@ -80,6 +81,14 @@ static EnumPropertyItem collision_bounds_items[] = {
 	//{OB_DYN_MESH, "DYNAMIC_MESH", 0, "Dynamic Mesh", ""},
 	{0, NULL, 0, NULL, NULL}};
 
+EnumPropertyItem metaelem_type_items[] = {
+	{MB_BALL, "BALL", ICON_META_BALL, "Ball", ""},
+	{MB_TUBE, "CAPSULE", ICON_META_CAPSULE, "Capsule", ""},
+	{MB_PLANE, "PLANE", ICON_META_PLANE, "Plane", ""},
+	{MB_ELIPSOID, "ELLIPSOID", ICON_META_ELLIPSOID, "Ellipsoid", ""}, // NOTE: typo at original definition!
+	{MB_CUBE, "CUBE", ICON_META_CUBE, "Cube", ""},
+	{0, NULL, 0, NULL, NULL}};
+
 /* used for 2 enums */
 #define OBTYPE_CU_CURVE {OB_CURVE, "CURVE", 0, "Curve", ""}
 #define OBTYPE_CU_SURF {OB_SURF, "SURFACE", 0, "Surface", ""}