Index: release/scripts/startup/bl_ui/properties_data_modifier.py
===================================================================
--- /Users/patrickboelens/Desktop/properties_data_modifier.py	(revision 44979)
+++ /Users/patrickboelens/Desktop/properties_data_modifier.py	(working copy)
@@ -318,6 +318,9 @@ class DATA_PT_modifiers(ModifierButtonsP
         col = split.column()
         col.label(text="Vertex Group:")
         col.prop_search(md, "vertex_group", ob, "vertex_groups", text="")
+        
+        layout.separator()
+        layout.prop(md, "influence", slider=True)
 
     def MASK(self, layout, ob, md):
         split = layout.split()

Index: source/blender/modifiers/intern/MOD_lattice.c
===================================================================
--- source/blender/modifiers/intern/MOD_lattice.c	(revision 44979)
+++ source/blender/modifiers/intern/MOD_lattice.c	(working copy)
@@ -49,6 +49,11 @@
 
 #include "MOD_util.h"
 
+static void initData(ModifierData *md)
+{
+	LatticeModifierData *lmd = (LatticeModifierData*) md;
+	lmd->influence = 1.0f;
+}
 
 static void copyData(ModifierData *md, ModifierData *target)
 {
@@ -115,7 +120,7 @@
 	modifier_vgroup_cache(md, vertexCos); /* if next modifier needs original vertices */
 	
 	lattice_deform_verts(lmd->object, ob, derivedData,
-	                     vertexCos, numVerts, lmd->name);
+	                     vertexCos, numVerts, lmd->name, lmd->influence);
 }
 
 static void deformVertsEM(
@@ -146,7 +151,7 @@
 	/* deformMatricesEM */  NULL,
 	/* applyModifier */     NULL,
 	/* applyModifierEM */   NULL,
-	/* initData */          NULL,
+	/* initData */          initData,
 	/* requiredDataMask */  requiredDataMask,
 	/* freeData */          NULL,
 	/* isDisabled */        isDisabled,
Index: source/blender/blenkernel/intern/lattice.c
===================================================================
--- source/blender/blenkernel/intern/lattice.c	(revision 44979)
+++ source/blender/blenkernel/intern/lattice.c	(working copy)
@@ -153,7 +153,7 @@
 
 		copy_m4_m4(mat, ltOb->obmat);
 		unit_m4(ltOb->obmat);
-		lattice_deform_verts(ltOb, NULL, NULL, vertexCos, uNew*vNew*wNew, NULL);
+		lattice_deform_verts(ltOb, NULL, NULL, vertexCos, uNew*vNew*wNew, NULL, 1.0f);
 		copy_m4_m4(ltOb->obmat, mat);
 
 		lt->typeu = typeu;
@@ -782,7 +782,7 @@
 }
 
 void lattice_deform_verts(Object *laOb, Object *target, DerivedMesh *dm,
-                          float (*vertexCos)[3], int numVerts, const char *vgroup)
+                          float (*vertexCos)[3], int numVerts, const char *vgroup, float influence)
 {
 	int a;
 	int use_vgroups;
@@ -819,12 +819,12 @@
 				weight= defvert_find_weight(dvert, index);
 
 				if (weight > 0.0f)
-					calc_latt_deform(laOb, vertexCos[a], weight);
+					calc_latt_deform(laOb, vertexCos[a], weight*influence);
 			}
 		}
 	} else {
 		for (a = 0; a < numVerts; a++) {
-			calc_latt_deform(laOb, vertexCos[a], 1.0f);
+			calc_latt_deform(laOb, vertexCos[a], influence);
 		}
 	}
 	end_latt_deform(laOb);
@@ -837,7 +837,7 @@
 
 		for (dl=dispbase->first; dl; dl=dl->next) {
 			lattice_deform_verts(ob->parent, ob, NULL,
-								 (float(*)[3]) dl->verts, dl->nr, NULL);
+								 (float(*)[3]) dl->verts, dl->nr, NULL, 1.0f);
 		}
 
 		return 1;
Index: source/blender/blenkernel/BKE_lattice.h
===================================================================
--- source/blender/blenkernel/BKE_lattice.h	(revision 44979)
+++ source/blender/blenkernel/BKE_lattice.h	(working copy)
@@ -63,7 +63,7 @@
 
 void lattice_deform_verts(struct Object *laOb, struct Object *target,
                           struct DerivedMesh *dm, float (*vertexCos)[3],
-                          int numVerts, const char *vgroup);
+                          int numVerts, const char *vgroup, float influence);
 void armature_deform_verts(struct Object *armOb, struct Object *target,
                            struct DerivedMesh *dm, float (*vertexCos)[3],
                            float (*defMats)[3][3], int numVerts, int deformflag,
Index: source/blender/makesdna/DNA_modifier_types.h
===================================================================
--- source/blender/makesdna/DNA_modifier_types.h	(revision 44979)
+++ source/blender/makesdna/DNA_modifier_types.h	(working copy)
@@ -135,6 +135,9 @@
 
 	struct Object *object;
 	char name[64];			/* optional vertexgroup name, MAX_VGROUP_NAME */
+    char pad[4];
+    float influence;
+
 } LatticeModifierData;
 
 typedef struct CurveModifierData {                                    \
Index: source/blender/makesrna/intern/rna_modifier.c
===================================================================
--- source/blender/makesrna/intern/rna_modifier.c	(revision 44979)
+++ source/blender/makesrna/intern/rna_modifier.c	(working copy)
@@ -960,6 +960,13 @@
 	                         "Name of Vertex Group which determines influence of modifier per point");
 	RNA_def_property_string_funcs(prop, NULL, NULL, "rna_LatticeModifier_vgroup_set");
 	RNA_def_property_update(prop, 0, "rna_Modifier_update");
+
+    prop = RNA_def_property(srna, "influence", PROP_FLOAT, PROP_NONE);
+    RNA_def_property_range(prop, -FLT_MAX, FLT_MAX);
+    RNA_def_property_ui_range(prop, 0, 1, 10, 2);
+    RNA_def_property_ui_text(prop, "Influence", "Strength of modifier effect");
+    RNA_def_property_update(prop, 0, "rna_Modifier_update");
+
 }
 
 static void rna_def_modifier_curve(BlenderRNA *brna)
Index: source/blender/blenloader/intern/readfile.c
===================================================================
--- source/blender/blenloader/intern/readfile.c	(revision 44979)
+++ source/blender/blenloader/intern/readfile.c	(working copy)
@@ -13292,6 +13292,21 @@
 		}
 	}
 
+    if (main->versionfile < 262 || (main->versionfile == 262 && main->subversionfile < 3))
+    {
+        Object *ob;
+        ModifierData *md;
+
+        for(ob = main->object.first; ob; ob = ob->id.next) {
+            for(md=ob->modifiers.first; md; md=md->next) {
+                if(md->type == eModifierType_Lattice) {
+                    LatticeModifierData *lmd = (LatticeModifierData *)md;
+                    lmd->influence = 1.0f;
+                }
+            }
+        }
+    }
+
 	{
 		/* Default for old files is to save particle rotations to pointcache */
 		ParticleSettings *part;