Long outstanding feature request: "Multi Modifier"

This allows to mix between the result of 2 modifiers, with both
using the same input state. This is useful for having a mesh deform
and armature deform working together.

However! This functionality could have been presented better...
this is actually Node editor stuff!

Now it works by adding a "MM" button, next to the "overall vgroup"
option. If MM is pressed, the input of this modifier is the same as
the input of the previous modifier.
Only the armature modifier has this option now...

5 files changed, 59 insertions, 10 deletions

diff --git a/source/blender/blenkernel/BKE_lattice.h b/source/blender/blenkernel/BKE_lattice.h
index 3dc4b49b52b..bf505fa23d7 100644
--- a/source/blender/blenkernel/BKE_lattice.h
+++ b/source/blender/blenkernel/BKE_lattice.h
@@ -64,8 +64,8 @@ void lattice_deform_verts(struct Object *laOb, struct Object *target,
                           int numVerts, char *vgroup);
 void armature_deform_verts(struct Object *armOb, struct Object *target,
                            struct DerivedMesh *dm, float (*vertexCos)[3],
-                           float (*defMats)[3][3], int numVerts,
-                           int deformflag, const char *defgrp_name);
+                           float (*defMats)[3][3], int numVerts, int deformflag, 
+						   float (*prevCos)[3], const char *defgrp_name);
 float (*lattice_getVertexCos(struct Object *ob, int *numVerts_r))[3];
 void lattice_applyVertexCos(struct Object *ob, float (*vertexCos)[3]);
 void lattice_calc_modifiers(struct Object *ob);
diff --git a/source/blender/blenkernel/intern/armature.c b/source/blender/blenkernel/intern/armature.c
index f688c573bc8..477ee982138 100644
--- a/source/blender/blenkernel/intern/armature.c
+++ b/source/blender/blenkernel/intern/armature.c
@@ -790,7 +790,8 @@ static void pchan_bone_deform(bPoseChannel *pchan, float weight, float *vec, Dua
 
 void armature_deform_verts(Object *armOb, Object *target, DerivedMesh *dm,
                            float (*vertexCos)[3], float (*defMats)[3][3],
-						   int numVerts, int deformflag, const char *defgrp_name)
+						   int numVerts, int deformflag, 
+						   float (*prevCos)[3], const char *defgrp_name)
 {
 	bPoseChannel *pchan, **defnrToPC = NULL;
 	MDeformVert *dverts = NULL;
@@ -881,11 +882,12 @@ void armature_deform_verts(Object *armOb, Object *target, DerivedMesh *dm,
 	for(i = 0; i < numVerts; i++) {
 		MDeformVert *dvert;
 		DualQuat sumdq, *dq = NULL;
-		float *co = vertexCos[i], dco[3];
+		float *co, dco[3];
 		float sumvec[3], summat[3][3];
 		float *vec = NULL, (*smat)[3] = NULL;
 		float contrib = 0.0f;
-		float armature_weight = 1.0f; /* default to 1 if no overall def group */
+		float armature_weight = 1.0f;	/* default to 1 if no overall def group */
+		float prevco_weight = 1.0f;		/* weight for optional cached vertexcos */
 		int	  j;
 
 		if(use_quaternion) {
@@ -917,11 +919,19 @@ void armature_deform_verts(Object *armOb, Object *target, DerivedMesh *dm,
 					break;
 				}
 			}
+			/* hackish: the blending factor can be used for blending with prevCos too */
+			if(prevCos) {
+				prevco_weight= armature_weight;
+				armature_weight= 1.0f;
+			}
 		}
 
 		/* check if there's any  point in calculating for this vert */
 		if(armature_weight == 0.0f) continue;
 		
+		/* get the coord we work on */
+		co= prevCos?prevCos[i]:vertexCos[i];
+		
 		/* Apply the object's matrix */
 		Mat4MulVecfl(premat, co);
 		
@@ -1005,6 +1015,15 @@ void armature_deform_verts(Object *armOb, Object *target, DerivedMesh *dm,
 		
 		/* always, check above code */
 		Mat4MulVecfl(postmat, co);
+		
+		
+		/* interpolate with previous modifier position using weight group */
+		if(prevCos && prevco_weight!=1.0f) {
+			float mw= 1.0f - prevco_weight;
+			vertexCos[i][0]= mw*vertexCos[i][0] + prevco_weight*co[0];
+			vertexCos[i][1]= mw*vertexCos[i][1] + prevco_weight*co[1];
+			vertexCos[i][2]= mw*vertexCos[i][2] + prevco_weight*co[2];
+		}
 	}
 
 	if(dualquats) MEM_freeN(dualquats);
diff --git a/source/blender/blenkernel/intern/modifier.c b/source/blender/blenkernel/intern/modifier.c
index c2f3880ec19..3a6611a2be7 100644
--- a/source/blender/blenkernel/intern/modifier.c
+++ b/source/blender/blenkernel/intern/modifier.c
@@ -238,12 +238,29 @@ static void latticeModifier_updateDepgraph(ModifierData *md, DagForest *forest,
 	}
 }
 
+static void modifier_vgroup_cache(ModifierData *md, float (*vertexCos)[3])
+{
+	md= md->next;
+	if(md) {
+		if(md->type==eModifierType_Armature) {
+			ArmatureModifierData *amd = (ArmatureModifierData*) md;
+			if(amd->multi)
+				amd->prevCos= MEM_dupallocN(vertexCos);
+		}
+		/* lattice/mesh modifier too */
+	}
+}
+
+
 static void latticeModifier_deformVerts(
                 ModifierData *md, Object *ob, DerivedMesh *derivedData,
                 float (*vertexCos)[3], int numVerts)
 {
 	LatticeModifierData *lmd = (LatticeModifierData*) md;
 
+
+	modifier_vgroup_cache(md, vertexCos); /* if next modifier needs original vertices */
+	
 	lattice_deform_verts(lmd->object, ob, derivedData,
 	                     vertexCos, numVerts, lmd->name);
 }
@@ -4664,8 +4681,16 @@ static void armatureModifier_deformVerts(
 {
 	ArmatureModifierData *amd = (ArmatureModifierData*) md;
 
+	modifier_vgroup_cache(md, vertexCos); /* if next modifier needs original vertices */
+	
 	armature_deform_verts(amd->object, ob, derivedData, vertexCos, NULL,
-	                      numVerts, amd->deformflag, amd->defgrp_name);
+	                      numVerts, amd->deformflag, 
+						  amd->prevCos, amd->defgrp_name);
+	/* free cache */
+	if(amd->prevCos) {
+		MEM_freeN(amd->prevCos);
+		amd->prevCos= NULL;
+	}
 }
 
 static void armatureModifier_deformVertsEM(
@@ -4678,7 +4703,7 @@ static void armatureModifier_deformVertsEM(
 	if(!derivedData) dm = CDDM_from_editmesh(editData, ob->data);
 
 	armature_deform_verts(amd->object, ob, dm, vertexCos, NULL, numVerts,
-	                      amd->deformflag, amd->defgrp_name);
+	                      amd->deformflag, NULL, amd->defgrp_name);
 
 	if(!derivedData) dm->release(dm);
 }
@@ -4694,7 +4719,7 @@ static void armatureModifier_deformMatricesEM(
 	if(!derivedData) dm = CDDM_from_editmesh(editData, ob->data);
 
 	armature_deform_verts(amd->object, ob, dm, vertexCos, defMats, numVerts,
-	                      amd->deformflag, amd->defgrp_name);
+	                      amd->deformflag, NULL, amd->defgrp_name);
 
 	if(!derivedData) dm->release(dm);
 }
@@ -5241,6 +5266,8 @@ static void meshdeformModifier_deformVerts(
 	else
 		dm= derivedData;
 
+	modifier_vgroup_cache(md, vertexCos); /* if next modifier needs original vertices */
+	
 	meshdeformModifier_do(md, ob, dm, vertexCos, numVerts);
 
 	if(dm != derivedData)
diff --git a/source/blender/makesdna/DNA_modifier_types.h b/source/blender/makesdna/DNA_modifier_types.h
index c55ae752ffb..0802fbf0e40 100644
--- a/source/blender/makesdna/DNA_modifier_types.h
+++ b/source/blender/makesdna/DNA_modifier_types.h
@@ -313,9 +313,10 @@ typedef struct WaveModifierData {
 typedef struct ArmatureModifierData {
 	ModifierData modifier;
 
-	short deformflag, pad1;		/* deformflag replaces armature->deformflag */
+	short deformflag, multi;		/* deformflag replaces armature->deformflag */
 	int pad2;
 	struct Object *object;
+	float *prevCos;		/* stored input of previous modifier, for vertexgroup blending */
 	char defgrp_name[32];
 } ArmatureModifierData;
 
diff --git a/source/blender/src/buttons_editing.c b/source/blender/src/buttons_editing.c
index c6c5668fdbd..9dcd7f9921b 100644
--- a/source/blender/src/buttons_editing.c
+++ b/source/blender/src/buttons_editing.c
@@ -1957,8 +1957,10 @@ static void draw_modifier(uiBlock *block, Object *ob, ModifierData *md, int *xco
 			ArmatureModifierData *amd = (ArmatureModifierData*) md;
 			uiDefIDPoinBut(block, modifier_testArmatureObj, ID_OB, B_CHANGEDEP, "Ob: ", lx, (cy-=19), buttonWidth,19, &amd->object, "Armature object to deform with");
 			
-			but=uiDefBut(block, TEX, B_MODIFIER_RECALC, "VGroup: ",				  lx, (cy-=19), buttonWidth,19, &amd->defgrp_name, 0.0, 31.0, 0, 0, "Vertex Group name to control overall armature influence");
+			but=uiDefBut(block, TEX, B_MODIFIER_RECALC, "VGroup: ",				  lx, (cy-=19), buttonWidth-40,19, &amd->defgrp_name, 0.0, 31.0, 0, 0, "Vertex Group name to control overall armature influence");
 			uiButSetCompleteFunc(but, autocomplete_vgroup, (void *)ob);
+			uiDefButS(block, TOG, B_ARM_RECALCDATA, "MM",	lx+buttonWidth-40,cy, 40, 20, &amd->multi, 0, 0, 0, 0, "MultiModifier: This modifier uses same input as previous modifier, and mixes using this vgroup");
+			
 			uiDefButBitS(block, TOG, ARM_DEF_VGROUP, B_ARM_RECALCDATA, "Vert.Groups",	lx,cy-=19,buttonWidth/2,20, &amd->deformflag, 0, 0, 0, 0, "Enable VertexGroups defining deform");
 			uiDefButBitS(block, TOG, ARM_DEF_ENVELOPE, B_ARM_RECALCDATA, "Envelopes",	lx+buttonWidth/2,cy,(buttonWidth + 1)/2,20, &amd->deformflag, 0, 0, 0, 0, "Enable Bone Envelopes defining deform");
 			uiDefButBitS(block, TOG, ARM_DEF_QUATERNION, B_ARM_RECALCDATA, "Quaternion",	lx,(cy-=19),buttonWidth/2,20, &amd->deformflag, 0, 0, 0, 0, "Enable deform rotation interpolation with Quaternions");