Cloth: option to use dynamic base mesh

This adds the ability for cloth simulations to respect changes in the underlying mesh.
So you can for instance, animate shape keys, armatures, or add any deformation modifiers (above the cloth modifier).

This is mainly useful for (but not limited to) cartoon animations,
where your character might stretch or change shape, and you want the clothes to follow accordingly.

D1903 by @LucaRood

1 files changed, 20 insertions, 2 deletions

diff --git a/source/blender/blenkernel/intern/cloth.c b/source/blender/blenkernel/intern/cloth.c
index 3e6df3ed77c..22d7cbafe41 100644
--- a/source/blender/blenkernel/intern/cloth.c
+++ b/source/blender/blenkernel/intern/cloth.c
@@ -58,6 +58,7 @@ static void cloth_to_object (Object *ob,  ClothModifierData *clmd, float (*verte
 static void cloth_from_mesh ( ClothModifierData *clmd, DerivedMesh *dm );
 static int cloth_from_object(Object *ob, ClothModifierData *clmd, DerivedMesh *dm, float framenr, int first);
 static void cloth_update_springs( ClothModifierData *clmd );
+static void cloth_update_verts( Object *ob, ClothModifierData *clmd, DerivedMesh *dm );
 static void cloth_update_spring_lengths( ClothModifierData *clmd, DerivedMesh *dm );
 static int cloth_build_springs ( ClothModifierData *clmd, DerivedMesh *dm );
 static void cloth_apply_vgroup ( ClothModifierData *clmd, DerivedMesh *dm );
@@ -368,10 +369,13 @@ static int do_step_cloth(Object *ob, ClothModifierData *clmd, DerivedMesh *resul
 
 	effectors = pdInitEffectors(clmd->scene, ob, NULL, clmd->sim_parms->effector_weights, true);
 
+	if (clmd->sim_parms->flags & CLOTH_SIMSETTINGS_FLAG_DYNAMIC_BASEMESH )
+		cloth_update_verts ( ob, clmd, result );
+
 	/* Support for dynamic vertex groups, changing from frame to frame */
 	cloth_apply_vgroup ( clmd, result );
 
-	if ( clmd->sim_parms->flags & CLOTH_SIMSETTINGS_FLAG_SEW )
+	if ( clmd->sim_parms->flags & (CLOTH_SIMSETTINGS_FLAG_SEW | CLOTH_SIMSETTINGS_FLAG_DYNAMIC_BASEMESH) )
 		cloth_update_spring_lengths ( clmd, result );
 
 	cloth_update_springs( clmd );
@@ -804,7 +808,7 @@ static int cloth_from_object(Object *ob, ClothModifierData *clmd, DerivedMesh *d
 	clmd->clothObject->springs = NULL;
 	clmd->clothObject->numsprings = -1;
 
-	if ( clmd->sim_parms->shapekey_rest )
+	if ( clmd->sim_parms->shapekey_rest && !(clmd->sim_parms->flags & CLOTH_SIMSETTINGS_FLAG_DYNAMIC_BASEMESH ) )
 		shapekey_rest = dm->getVertDataArray ( dm, CD_CLOTH_ORCO );
 
 	mvert = dm->getVertArray (dm);
@@ -1180,6 +1184,20 @@ static void cloth_update_springs( ClothModifierData *clmd )
 	cloth_hair_update_bending_targets(clmd);
 }
 
+/* Update rest verts, for dynamically deformable cloth */
+static void cloth_update_verts( Object *ob, ClothModifierData *clmd, DerivedMesh *dm )
+{
+	unsigned int i = 0;
+	MVert *mvert = dm->getVertArray (dm);
+	ClothVertex *verts = clmd->clothObject->verts;
+
+	/* vertex count is already ensured to match */
+	for ( i = 0; i < dm->getNumVerts(dm); i++, verts++ ) {
+		copy_v3_v3(verts->xrest, mvert[i].co);
+		mul_m4_v3(ob->obmat, verts->xrest);
+	}
+}
+
 /* Update spring rest lenght, for dynamically deformable cloth */
 static void cloth_update_spring_lengths( ClothModifierData *clmd, DerivedMesh *dm )
 {