== Limit Distance Constraint ==

Added a new constraint, "Limit Distance". This constraint defines a 'virtual sphere' around the target which the owner can be made to stay inside, outside, or on the surface of it. 

This constraint is best used when applied using the Ctrl-Alt-C hotkey, as the radius is set correctly that way. 
One usage, is to prevent the target of an IK-chain from straying away from the chain. Care should be taken to not use a member of the IK-chain as the target though.

Description of Variables:
* 'Dist' - Radius of virtual sphere
* 'R' - Click on this to recalculate the 'Dist' value (note: like the 'R' button in the StretchTo constraint, this is currently buggy)
' Mode' - This menu gives different options for how the limiting sphere should act. The mode names are self explanatory.
* 'Soft' and 'SoftDistance' - currently not functional (so settings are hidden). These are used to define a smaller radius around the sphere of influence where a non-linear relationship between input and resulting locations occurs to prevent the owner 'crashing' into the sphere.

source/blender/blenkernel/intern/constraint.c

@@ -2382,6 +2382,118 @@ static bConstraintTypeInfo CTI_LOCKTRACK = {
 	locktrack_evaluate /* evaluate */
 };
 
+/* ---------- Limit Distance Constraint ----------- */
+
+static void distlimit_new_data (void *cdata)
+{
+	bDistLimitConstraint *data= (bDistLimitConstraint *)cdata;
+	
+	data->dist= 0.0;
+}
+
+static void distlimit_get_tars (bConstraint *con, ListBase *list)
+{
+	if (con && list) {
+		bDistLimitConstraint *data= con->data;
+		bConstraintTarget *ct;
+		
+		/* standard target-getting macro for single-target constraints */
+		SINGLETARGET_GET_TARS(con, data->tar, data->subtarget, ct, list)
+	}
+}
+
+static void distlimit_flush_tars (bConstraint *con, ListBase *list, short nocopy)
+{
+	if (con && list) {
+		bDistLimitConstraint *data= con->data;
+		bConstraintTarget *ct= list->first;
+		
+		/* the following macro is used for all standard single-target constraints */
+		SINGLETARGET_FLUSH_TARS(con, data->tar, data->subtarget, ct, list, nocopy)
+	}
+}
+
+static void distlimit_evaluate (bConstraint *con, bConstraintOb *cob, ListBase *targets)
+{
+	bDistLimitConstraint *data= con->data;
+	bConstraintTarget *ct= targets->first;
+	
+	/* only evaluate if there is a target */
+	if (VALID_CONS_TARGET(ct)) {
+		float dvec[3], dist=0.0f, sfac=1.0f;
+		short clamp_surf= 0;
+		
+		/* calculate our current distance from the target */
+		dist= VecLenf(cob->matrix[3], ct->matrix[3]);
+		
+		/* set distance (flag is only set when user demands it) */
+		if (data->dist == 0)
+			data->dist= dist;
+		
+		/* check if we're which way to clamp from, and calculate interpolation factor (if needed) */
+		if (data->mode == LIMITDIST_OUTSIDE) {
+			/* if inside, then move to surface */
+			if (dist <= data->dist) {
+				clamp_surf= 1;
+				sfac= data->dist / dist;
+			}
+			/* if soft-distance is enabled, start fading once owner is dist+softdist from the target */
+			else if (data->flag & LIMITDIST_USESOFT) {
+				if (dist <= (data->dist + data->soft)) {
+					
+				}
+			}
+		}
+		else if (data->mode == LIMITDIST_INSIDE) {
+			/* if outside, then move to surface */
+			if (dist >= data->dist) {
+				clamp_surf= 1;
+				sfac= data->dist / dist;
+			}
+			/* if soft-distance is enabled, start fading once owner is dist-soft from the target */
+			else if (data->flag & LIMITDIST_USESOFT) {
+				// FIXME: there's a problem with "jumping" when this kicks in
+				if (dist >= (data->dist - data->soft)) {
+					sfac = data->soft*(1.0 - exp(-(dist - data->dist)/data->soft)) + data->dist;
+					sfac /= dist;
+					
+					clamp_surf= 1;
+				}
+			}
+		}
+		else {
+			if (IS_EQ(dist, data->dist)==0) {
+				clamp_surf= 1;
+				sfac= data->dist / dist;
+			}
+		}
+		
+		/* clamp to 'surface' (i.e. move owner so that dist == data->dist) */
+		if (clamp_surf) {
+			/* simply interpolate along line formed by target -> owner */
+			VecLerpf(dvec, ct->matrix[3], cob->matrix[3], sfac);
+			
+			/* copy new vector onto owner */
+			VECCOPY(cob->matrix[3], dvec);
+		}
+	}
+}
+
+static bConstraintTypeInfo CTI_DISTLIMIT = {
+	CONSTRAINT_TYPE_DISTLIMIT, /* type */
+	sizeof(bDistLimitConstraint), /* size */
+	"Limit Distance", /* name */
+	"bDistLimitConstraint", /* struct name */
+	NULL, /* free data */
+	NULL, /* relink data */
+	NULL, /* copy data */
+	distlimit_new_data, /* new data */
+	distlimit_get_tars, /* get constraint targets */
+	distlimit_flush_tars, /* flush constraint targets */
+	default_get_tarmat, /* get a target matrix */
+	distlimit_evaluate /* evaluate */
+};
+
 /* ---------- Stretch To ------------ */
 
 static void stretchto_new_data (void *cdata)
@@ -3067,7 +3179,7 @@ static void constraints_init_typeinfo () {
 	constraintsTypeInfo[11]= &CTI_PYTHON;			/* Python/Script Constraint */
 	constraintsTypeInfo[12]= &CTI_ACTION;			/* Action Constraint */
 	constraintsTypeInfo[13]= &CTI_LOCKTRACK;		/* Locked-Track Constraint */
-	constraintsTypeInfo[14]= NULL;					/* 'Distance Limit' Constraint */
+	constraintsTypeInfo[14]= &CTI_DISTLIMIT;		/* Limit Distance Constraint */
 	constraintsTypeInfo[15]= &CTI_STRETCHTO; 		/* StretchTo Constaint */ 
 	constraintsTypeInfo[16]= &CTI_MINMAX;  			/* Floor Constraint */
 	constraintsTypeInfo[17]= &CTI_RIGIDBODYJOINT;	/* RigidBody Constraint */

source/blender/blenloader/intern/readfile.c

@@ -1752,6 +1752,13 @@ static void lib_link_constraints(FileData *fd, ID *id, ListBase *conlist)
 				data->tar = newlibadr(fd, id->lib, data->tar);
 			}
 			break;
+		case CONSTRAINT_TYPE_DISTLIMIT:
+			{
+				bDistLimitConstraint *data;
+				data= ((bDistLimitConstraint*)con->data);
+				data->tar = newlibadr(fd, id->lib, data->tar);
+			}
+			break;
 		case CONSTRAINT_TYPE_NULL:
 			break;
 		}
@@ -1765,6 +1772,7 @@ static void direct_link_constraints(FileData *fd, ListBase *lb)
 	link_list(fd, lb);
 	for (cons=lb->first; cons; cons=cons->next) {
 		cons->data = newdataadr(fd, cons->data);
+		
 		if (cons->type == CONSTRAINT_TYPE_PYTHON) {
 			bPythonConstraint *data= cons->data;
 			link_list(fd, &data->targets);
@@ -7807,6 +7815,12 @@ static void expand_constraints(FileData *fd, Main *mainvar, ListBase *lb)
 				expand_doit(fd, mainvar, data->tar);
 			}
 			break;
+		case CONSTRAINT_TYPE_DISTLIMIT:	
+			{
+				bDistLimitConstraint *data = (bDistLimitConstraint*)curcon->data;
+				expand_doit(fd, mainvar, data->tar);
+			}
+			break;
 		default:
 			break;
 		}

source/blender/include/butspace.h

@@ -694,7 +694,7 @@ enum {
 	B_CONSTRAINT_ADD_ACTION,
 	B_CONSTRAINT_ADD_LOCKTRACK,
 	B_CONSTRAINT_ADD_FOLLOWPATH,
-	B_CONSTRAINT_ADD_DISTANCELIMIT,
+	B_CONSTRAINT_ADD_DISTLIMIT,
 	B_CONSTRAINT_ADD_STRETCHTO,
 	B_CONSTRAINT_ADD_LOCLIMIT,
 	B_CONSTRAINT_ADD_ROTLIMIT,

source/blender/makesdna/DNA_constraint_types.h

@@ -307,6 +307,19 @@ typedef struct bSizeLimitConstraint {
 	short		flag2;
 } bSizeLimitConstraint;
 
+/* Limit Distance Constraint */
+typedef struct bDistLimitConstraint {
+	Object 		*tar;
+	char 		subtarget[32];
+	
+	float 		dist;			/* distance (radius of clamping sphere) from target */
+	float		soft;			/* distance from clamping-sphere to start applying 'fade' */
+	
+	short		flag;			/* settings */
+	short 		mode;			/* how to limit in relation to clamping sphere */
+	int 		pad;
+} bDistLimitConstraint;
+
 /* ------------------------------------------ */
 
 /* bConstraint->type 
@@ -328,13 +341,14 @@ typedef enum B_CONSTAINT_TYPES {
 	CONSTRAINT_TYPE_PYTHON,				/* Unimplemented no longer :) - Aligorith. Scripts */
 	CONSTRAINT_TYPE_ACTION,
 	CONSTRAINT_TYPE_LOCKTRACK,			/* New Tracking constraint that locks an axis in place - theeth */
-	CONSTRAINT_TYPE_DISTANCELIMIT,		/* was never properly coded - removed! */
+	CONSTRAINT_TYPE_DISTLIMIT,			/* limit distance */
 	CONSTRAINT_TYPE_STRETCHTO, 			/* claiming this to be mine :) is in tuhopuu bjornmose */ 
 	CONSTRAINT_TYPE_MINMAX,  			/* floor constraint */
 	CONSTRAINT_TYPE_RIGIDBODYJOINT,		/* rigidbody constraint */
 	CONSTRAINT_TYPE_CLAMPTO, 			/* clampto constraint */	
 	CONSTRAINT_TYPE_TRANSFORM,			/* transformation (loc/rot/size -> loc/rot/size) constraint */	
 	
+	
 	/* NOTE: everytime a new constraint is added, update this */
 	NUM_CONSTRAINT_TYPES= CONSTRAINT_TYPE_TRANSFORM
 } B_CONSTRAINT_TYPES; 
@@ -479,6 +493,15 @@ typedef enum B_CONSTRAINTCHANNEL_FLAG {
 	/* for all Limit constraints - allow to be used during transform? */
 #define LIMIT_TRANSFORM 0x02
 
+/* distance limit constraint */
+	/* bDistLimitConstraint->flag */
+#define LIMITDIST_USESOFT		(1<<0)
+
+	/* bDistLimitConstraint->mode */
+#define LIMITDIST_INSIDE		0
+#define LIMITDIST_OUTSIDE		1
+#define LIMITDIST_ONSURFACE		2
+	
 /* python constraint -> flag */
 #define PYCON_USETARGETS	0x01
 #define PYCON_SCRIPTERROR	0x02

source/blender/src/buttons_object.c

@@ -1439,6 +1439,54 @@ static void draw_constraint (uiBlock *block, ListBase *list, bConstraint *con, s
 				draw_constraint_spaceselect(block, con, *xco, *yco-130, is_armature_owner(ob), -1);
 			}
 			break;
+		case CONSTRAINT_TYPE_DISTLIMIT:
+			{
+				bDistLimitConstraint *data = con->data;
+				
+				height = 105;
+				uiDefBut(block, ROUNDBOX, B_DIFF, "", *xco-10, *yco-height, width+40,height-1, NULL, 5.0, 0.0, 12, rb_col, ""); 
+				
+				uiDefBut(block, LABEL, B_CONSTRAINT_TEST, "Target:", *xco+65, *yco-24, 50, 18, NULL, 0.0, 0.0, 0.0, 0.0, ""); 
+				
+				/* Draw target parameters */
+				uiBlockBeginAlign(block);
+					uiDefIDPoinBut(block, test_obpoin_but, ID_OB, B_CONSTRAINT_CHANGETARGET, "OB:", *xco+120, *yco-24, 135, 18, &data->tar, "Target Object"); 
+					
+					if (is_armature_target(data->tar)) {
+						but=uiDefBut(block, TEX, B_CONSTRAINT_CHANGETARGET, "BO:", *xco+120, *yco-42,135,18, &data->subtarget, 0, 24, 0, 0, "Subtarget Bone");
+						uiButSetCompleteFunc(but, autocomplete_bone, (void *)data->tar);
+					}
+					else if (is_geom_target(data->tar)) {
+						but= uiDefBut(block, TEX, B_CONSTRAINT_CHANGETARGET, "VG:", *xco+120, *yco-42,135,18, &data->subtarget, 0, 24, 0, 0, "Name of Vertex Group defining 'target' points");
+						uiButSetCompleteFunc(but, autocomplete_vgroup, (void *)data->tar);
+					}
+					else {
+						strcpy(data->subtarget, "");
+					}
+				uiBlockEndAlign(block);
+				
+				uiBlockBeginAlign(block);
+					if (is_armature_target(data->tar)) {
+						uiDefButF(block, BUT, B_CONSTRAINT_TEST, "R", *xco, *yco-60, 20, 18, &data->dist, 0, 0, 0, 0, "Recalculate distance"); 
+						uiDefButF(block, NUM, B_CONSTRAINT_TEST, "Distance:", *xco+18, *yco-60,139,18, &data->dist, 0.0, 100, 0.5, 0.5, "Radius of limiting sphere");
+						uiDefButF(block, NUM, B_CONSTRAINT_TEST, "Head/Tail:", *xco+155, *yco-60,100,18, &con->headtail, 0.0, 1, 0.1, 0.1, "Target along length of bone: Head=0, Tail=1");
+					}
+					else {
+						uiDefButF(block, BUT, B_CONSTRAINT_TEST, "R", *xco, *yco-60, 20, 18, &data->dist, 0, 0, 0, 0, "Recalculate distance"); 
+						uiDefButF(block, NUM, B_CONSTRAINT_TEST, "Distance:", *xco+18, *yco-60, 237, 18, &data->dist, 0.0, 100, 0.5, 0.5, "Radius of limiting sphere");
+					}
+					
+					/* disabled soft-distance controls... currently it doesn't work yet. It was intended to be used for soft-ik (see xsi-blog for details) */
+#if 0
+					uiDefButBitS(block, TOG, LIMITDIST_USESOFT, B_CONSTRAINT_TEST, "Soft", *xco, *yco-82, 50, 18, &data->flag, 0, 24, 0, 0, "Enables soft-distance");
+					if (data->flag & LIMITDIST_USESOFT)
+						uiDefButF(block, NUM, B_CONSTRAINT_TEST, "Soft-Distance:", *xco+50, *yco-82, 187, 18, &data->soft, 0.0, 100, 0.5, 0.5, "Distance surrounding radius when transforms should get 'delayed'");
+#endif
+				uiBlockEndAlign(block);
+				
+				uiDefButS(block, MENU, B_CONSTRAINT_TEST, "Limit Mode%t|Inside %x0|Outside %x1|Surface %x2", *xco+((width/2)-50), *yco-104, 100, 18, &data->mode, 0, 24, 0, 0, "Distances in relation to sphere of influence to allow");
+			}
+			break;
 		case CONSTRAINT_TYPE_RIGIDBODYJOINT:
 			{
 				bRigidBodyJointConstraint *data = con->data;
@@ -1748,6 +1796,7 @@ static uiBlock *add_constraintmenu(void *arg_unused)
 	uiDefBut(block, BUTM, B_CONSTRAINT_ADD_LOCLIMIT, "Limit Location", 0, yco-=20, 160, 19, NULL, 0.0, 0.0, 1, 0, "");
 	uiDefBut(block, BUTM, B_CONSTRAINT_ADD_ROTLIMIT, "Limit Rotation", 0, yco-=20, 160, 19, NULL, 0.0, 0.0, 1, 0, "");
 	uiDefBut(block, BUTM, B_CONSTRAINT_ADD_SIZELIMIT, "Limit Scale", 0, yco-=20, 160, 19, NULL, 0.0, 0.0, 1, 0, "");
+	uiDefBut(block, BUTM, B_CONSTRAINT_ADD_DISTLIMIT, "Limit Distance", 0, yco-=20, 160, 19, NULL, 0.0, 0.0, 1, 0, "");
 	
 	uiDefBut(block, SEPR, 0, "",					0, yco-=6, 120, 6, NULL, 0.0, 0.0, 0, 0, "");
 	
@@ -1980,6 +2029,14 @@ void do_constraintbuts(unsigned short event)
 			BIF_undo_push("Add constraint");
 		}
 		break;
+	case B_CONSTRAINT_ADD_DISTLIMIT:
+		{
+			con = add_new_constraint(CONSTRAINT_TYPE_DISTLIMIT);
+			add_constraint_to_active(ob, con);
+			
+			BIF_undo_push("Add constraint");
+		}
+		break;
 
 	default:
 		break;

source/blender/src/editconstraint.c

@@ -364,21 +364,21 @@ void add_constraint (short only_IK)
 	else {
 		if (pchanact) {
 			if (pchansel)
-				nr= pupmenu("Add Constraint to Active Bone%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|%l|Track To%x3|Floor%x4|Locked Track%x5|Stretch To%x7|%l|Action%x16|Script%x18");
+				nr= pupmenu("Add Constraint to Active Bone%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|Limit Distance%x21|%l|Track To%x3|Floor%x4|Locked Track%x5|Stretch To%x7|%l|Action%x16|Script%x18");
 			else if ((obsel) && (obsel->type==OB_CURVE))
-				nr= pupmenu("Add Constraint to Active Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|%l|Track To%x3|Floor%x4|Locked Track%x5|Follow Path%x6|Clamp To%x17|Stretch To%x7|%l|Action%x16|Script%x18");
+				nr= pupmenu("Add Constraint to Active Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|Limit Distance%x21|%l|Track To%x3|Floor%x4|Locked Track%x5|Follow Path%x6|Clamp To%x17|Stretch To%x7|%l|Action%x16|Script%x18");
 			else if (obsel)
-				nr= pupmenu("Add Constraint to Active Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|%l|Track To%x3|Floor%x4|Locked Track%x5|Stretch To%x7|%l|Action%x16|Script%x18");
+				nr= pupmenu("Add Constraint to Active Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|Limit Distance%x21|%l|Track To%x3|Floor%x4|Locked Track%x5|Stretch To%x7|%l|Action%x16|Script%x18");
 			else
-				nr= pupmenu("Add Constraint to New Empty Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|%l|Track To%x3|Floor%x4|Locked Track%x5|Stretch To%x7|%l|Action%x16|Script%x18");
+				nr= pupmenu("Add Constraint to New Empty Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|Limit Distance%x21|%l|Track To%x3|Floor%x4|Locked Track%x5|Stretch To%x7|%l|Action%x16|Script%x18");
 		}
 		else {
 			if ((obsel) && (obsel->type==OB_CURVE))
-				nr= pupmenu("Add Constraint to Active Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|%l|Track To%x3|Floor%x4|Locked Track%x5|Follow Path%x6|Clamp To%x17|%l|Action%x16|Script%x18");
+				nr= pupmenu("Add Constraint to Active Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|Limit Distance%x21|%l|Track To%x3|Floor%x4|Locked Track%x5|Follow Path%x6|Clamp To%x17|%l|Action%x16|Script%x18");
 			else if (obsel)
-				nr= pupmenu("Add Constraint to Active Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|%l|Track To%x3|Floor%x4|Locked Track%x5|%l|Action%x16|Script%x18");
+				nr= pupmenu("Add Constraint to Active Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|Limit Distance%x21|%l|Track To%x3|Floor%x4|Locked Track%x5|%l|Action%x16|Script%x18");
 			else
-				nr= pupmenu("Add Constraint to New Empty Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|%l|Track To%x3|Floor%x4|Locked Track%x5|%l|Action%x16|Script%x18");
+				nr= pupmenu("Add Constraint to New Empty Object%t|Child Of%x19|Transformation%x20|%l|Copy Location%x1|Copy Rotation%x2|Copy Scale%x8|%l|Limit Location%x13|Limit Rotation%x14|Limit Scale%x15|Limit Distance%x21|%l|Track To%x3|Floor%x4|Locked Track%x5|%l|Action%x16|Script%x18");
 		}
 	}
 	
@@ -475,6 +475,7 @@ void add_constraint (short only_IK)
 			}
 		}
 		else if (nr==20) con = add_new_constraint(CONSTRAINT_TYPE_TRANSFORM);
+		else if (nr==21) con = add_new_constraint(CONSTRAINT_TYPE_DISTLIMIT);
 		
 		if (con==NULL) return;	/* paranoia */
 		

source/blender/src/editipo.c

@@ -2515,7 +2515,7 @@ static int match_adr_constraint(ID * id, int blocktype, char *actname, int adrco
 						case CONSTRAINT_TYPE_LOCKTRACK:
 							if (searchtype==2) foundmatch=1;
 							break;
-						case CONSTRAINT_TYPE_DISTANCELIMIT:
+						case CONSTRAINT_TYPE_DISTLIMIT:
 							if (searchtype==1) foundmatch=1;
 							break;
 						case CONSTRAINT_TYPE_MINMAX: