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, 16 insertions, 13 deletions

diff --git a/source/blender/modifiers/intern/MOD_array.c b/source/blender/modifiers/intern/MOD_array.c
index 9decf8e3bb5..597320c3887 100644
--- a/source/blender/modifiers/intern/MOD_array.c
+++ b/source/blender/modifiers/intern/MOD_array.c
@@ -57,6 +57,7 @@
 #include "MOD_util.h"
 
 #include "DEG_depsgraph.h"
+#include "DEG_depsgraph_query.h"
 
 static void initData(ModifierData *md)
 {
@@ -364,7 +365,7 @@ static Mesh *arrayModifier_doArray(
 
 	const bool use_merge = (amd->flags & MOD_ARR_MERGE) != 0;
 	const bool use_recalc_normals = (mesh->runtime.cd_dirty_vert & CD_MASK_NORMAL) || use_merge;
-	const bool use_offset_ob = ((amd->offset_type & MOD_ARR_OFF_OBJ) && amd->offset_ob);
+	const bool use_offset_ob = ((amd->offset_type & MOD_ARR_OFF_OBJ) && amd->offset_ob != NULL);
 
 	int start_cap_nverts = 0, start_cap_nedges = 0, start_cap_npolys = 0, start_cap_nloops = 0;
 	int end_cap_nverts = 0, end_cap_nedges = 0, end_cap_npolys = 0, end_cap_nloops = 0;
@@ -387,11 +388,12 @@ static Mesh *arrayModifier_doArray(
 
 	count = amd->count;
 
-	if (amd->start_cap && amd->start_cap != ctx->object && amd->start_cap->type == OB_MESH) {
+	Object *start_cap_ob = DEG_get_evaluated_object(ctx->depsgraph, amd->start_cap);
+	if (start_cap_ob && start_cap_ob != ctx->object && start_cap_ob->type == OB_MESH) {
 		vgroup_start_cap_remap = BKE_object_defgroup_index_map_create(
-		                             amd->start_cap, ctx->object, &vgroup_start_cap_remap_len);
+		                             start_cap_ob, ctx->object, &vgroup_start_cap_remap_len);
 
-		start_cap_mesh = BKE_modifier_get_evaluated_mesh_from_evaluated_object(amd->start_cap, &start_cap_mesh_free);
+		start_cap_mesh = BKE_modifier_get_evaluated_mesh_from_evaluated_object(start_cap_ob, &start_cap_mesh_free);
 		if (start_cap_mesh) {
 			start_cap_nverts = start_cap_mesh->totvert;
 			start_cap_nedges = start_cap_mesh->totedge;
@@ -399,11 +401,12 @@ static Mesh *arrayModifier_doArray(
 			start_cap_npolys = start_cap_mesh->totpoly;
 		}
 	}
-	if (amd->end_cap && amd->end_cap != ctx->object && amd->end_cap->type == OB_MESH) {
+	Object *end_cap_ob = DEG_get_evaluated_object(ctx->depsgraph, amd->end_cap);
+	if (end_cap_ob && end_cap_ob != ctx->object && end_cap_ob->type == OB_MESH) {
 		vgroup_end_cap_remap = BKE_object_defgroup_index_map_create(
-		                           amd->end_cap, ctx->object, &vgroup_end_cap_remap_len);
+		                           end_cap_ob, ctx->object, &vgroup_end_cap_remap_len);
 
-		end_cap_mesh = BKE_modifier_get_evaluated_mesh_from_evaluated_object(amd->end_cap, &end_cap_mesh_free);
+		end_cap_mesh = BKE_modifier_get_evaluated_mesh_from_evaluated_object(end_cap_ob, &end_cap_mesh_free);
 		if (end_cap_mesh) {
 			end_cap_nverts = end_cap_mesh->totvert;
 			end_cap_nedges = end_cap_mesh->totedge;
@@ -444,8 +447,7 @@ static Mesh *arrayModifier_doArray(
 		else
 			unit_m4(obinv);
 
-		mul_m4_series(result_mat, offset,
-		              obinv, amd->offset_ob->obmat);
+		mul_m4_series(result_mat, offset, obinv, DEG_get_evaluated_object(ctx->depsgraph, amd->offset_ob)->obmat);
 		copy_m4_m4(offset, result_mat);
 	}
 
@@ -453,12 +455,13 @@ static Mesh *arrayModifier_doArray(
 	mat4_to_size(scale, offset);
 	offset_has_scale = !is_one_v3(scale);
 
-	if (amd->fit_type == MOD_ARR_FITCURVE && amd->curve_ob) {
-		Curve *cu = amd->curve_ob->data;
+	if (amd->fit_type == MOD_ARR_FITCURVE && amd->curve_ob != NULL) {
+		Object *curve_ob = DEG_get_evaluated_object(ctx->depsgraph, amd->curve_ob);
+		Curve *cu = curve_ob->data;
 		if (cu) {
-			CurveCache *curve_cache = amd->curve_ob->runtime.curve_cache;
+			CurveCache *curve_cache = curve_ob->runtime.curve_cache;
 			if (curve_cache != NULL && curve_cache->path != NULL) {
-				float scale_fac = mat4_to_scale(amd->curve_ob->obmat);
+				float scale_fac = mat4_to_scale(curve_ob->obmat);
 				length = scale_fac * curve_cache->path->totdist;
 			}
 		}