Fix modifiers evaluation outside of depsgraph/CoW context.

Fix T58237: Exporters: Curve Modifier not applied when "apply modifiers" are selected.
Fix T58856: Python: "to_mesh" broken in 2.8.

...And many other cases... ;)

Thing is, we need target IDs to always be evaluated ones (at least I
cannot see any case where having orig ones is desired effect here).
Depsgraph/Cow system ensures us that when modifiers are evaluated by it,
but they can also be called outside of this context, e.g. when doing
binding, or object conversion...

So we need to ensure in modifiers code that we actually are always
working with eval data for those targets.

Note that I did not touch to physics modifiers, those are a bit touchy
and rather not 'fix' something there until proven broken!

1 files changed, 6 insertions, 4 deletions

diff --git a/source/blender/modifiers/intern/MOD_meshdeform.c b/source/blender/modifiers/intern/MOD_meshdeform.c
index d3450e61709..ae027c64626 100644
--- a/source/blender/modifiers/intern/MOD_meshdeform.c
+++ b/source/blender/modifiers/intern/MOD_meshdeform.c
@@ -295,7 +295,7 @@ static void meshdeformModifier_do(
 
 	static int recursive_bind_sentinel = 0;
 
-	if (!mmd->object || (!mmd->bindcagecos && !mmd->bindfunc))
+	if (mmd->object == NULL || (mmd->bindcagecos == NULL && mmd->bindfunc == NULL))
 		return;
 
 	/* Get cage mesh.
@@ -308,21 +308,23 @@ static void meshdeformModifier_do(
 	 *
 	 * We'll support this case once granular dependency graph is landed.
 	 */
-	cagemesh = BKE_modifier_get_evaluated_mesh_from_evaluated_object(mmd->object, &free_cagemesh);
+	Object *ob_target = DEG_get_evaluated_object(ctx->depsgraph, mmd->object);
+	cagemesh = BKE_modifier_get_evaluated_mesh_from_evaluated_object(ob_target, &free_cagemesh);
+#if 0  /* This shall not be needed if we always get evaluated target object... */
 	if (cagemesh == NULL && mmd->bindcagecos == NULL && ob == DEG_get_original_object(ob)) {
 		/* Special case, binding happens outside of depsgraph evaluation, so we can build our own
 		 * target mesh if needed. */
 		cagemesh = mesh_create_eval_final_view(ctx->depsgraph, DEG_get_input_scene(ctx->depsgraph), mmd->object, 0);
 		free_cagemesh = cagemesh != NULL;
 	}
-
+#endif
 	if (cagemesh == NULL) {
 		modifier_setError(md, "Cannot get mesh from cage object");
 		return;
 	}
 
 	/* compute matrices to go in and out of cage object space */
-	invert_m4_m4(imat, mmd->object->obmat);
+	invert_m4_m4(imat, ob_target->obmat);
 	mul_m4_m4m4(cagemat, imat, ob->obmat);
 	mul_m4_m4m4(cmat, mmd->bindmat, cagemat);
 	invert_m4_m4(iobmat, cmat);