rigidbody: Add rigid body constraints

Constraints connect two rigid bodies.
Depending on which constraint is used different degrees of freedom
are limited, e.g. a hinge constraint only allows the objects to rotate
around a common axis.

Constraints are implemented as individual objects and bahave similar to
rigid bodies in terms of adding/removing/validating.

The position and orientation of the constraint object is the pivot point
of the constraint.

Constraints have their own group in the rigid body world.

To make connecting rigid bodies easier, there is a "Connect" operator that
creates an empty objects with a rigid body constraint connecting the selected
objects to active.

Currently the following constraints are implemented:
* Fixed
* Point
* Hinge
* Slider
* Piston
* Generic

Note: constraint limits aren't animatable yet).

2 files changed, 22 insertions, 3 deletions

diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index edb033e80f8..070cb4676a1 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -4363,6 +4363,11 @@ static void lib_link_object(FileData *fd, Main *main)
 			
 			lib_link_particlesystems(fd, ob, &ob->id, &ob->particlesystem);
 			lib_link_modifiers(fd, ob);
+
+			if (ob->rigidbody_constraint) {
+				ob->rigidbody_constraint->ob1 = newlibadr(fd, ob->id.lib, ob->rigidbody_constraint->ob1);
+				ob->rigidbody_constraint->ob2 = newlibadr(fd, ob->id.lib, ob->rigidbody_constraint->ob2);
+			}
 		}
 	}
 	
@@ -4797,7 +4802,10 @@ static void direct_link_object(FileData *fd, Object *ob)
 		rbo->physics_object = NULL;
 		rbo->physics_shape = NULL;
 	}
-	
+	ob->rigidbody_constraint = newdataadr(fd, ob->rigidbody_constraint);
+	if (ob->rigidbody_constraint)
+		ob->rigidbody_constraint->physics_constraint = NULL;
+
 	link_list(fd, &ob->particlesystem);
 	direct_link_particlesystems(fd, &ob->particlesystem);
 	
@@ -5021,6 +5029,8 @@ static void lib_link_scene(FileData *fd, Main *main)
 				RigidBodyWorld *rbw = sce->rigidbody_world;
 				if (rbw->group)
 					rbw->group = newlibadr(fd, sce->id.lib, rbw->group);
+				if (rbw->constraints)
+					rbw->constraints = newlibadr(fd, sce->id.lib, rbw->constraints);
 				if (rbw->effector_weights)
 					rbw->effector_weights->group = newlibadr(fd, sce->id.lib, rbw->effector_weights->group);
 			}
@@ -9679,7 +9689,12 @@ static void expand_object(FileData *fd, Main *mainvar, Object *ob)
 	
 	if (ob->pd && ob->pd->tex)
 		expand_doit(fd, mainvar, ob->pd->tex);
-	
+
+	if (ob->rigidbody_constraint) {
+		expand_doit(fd, mainvar, ob->rigidbody_constraint->ob1);
+		expand_doit(fd, mainvar, ob->rigidbody_constraint->ob2);
+	}
+
 }
 
 static void expand_scene(FileData *fd, Main *mainvar, Scene *sce)
@@ -9728,6 +9743,7 @@ static void expand_scene(FileData *fd, Main *mainvar, Scene *sce)
 	
 	if (sce->rigidbody_world) {
 		expand_doit(fd, mainvar, sce->rigidbody_world->group);
+		expand_doit(fd, mainvar, sce->rigidbody_world->constraints);
 	}
 
 #ifdef DURIAN_CAMERA_SWITCH
diff --git a/source/blender/blenloader/intern/writefile.c b/source/blender/blenloader/intern/writefile.c
index ebd752c0118..e7a53670849 100644
--- a/source/blender/blenloader/intern/writefile.c
+++ b/source/blender/blenloader/intern/writefile.c
@@ -1492,7 +1492,10 @@ static void write_objects(WriteData *wd, ListBase *idbase)
 				// TODO: if any extra data is added to handle duplis, will need separate function then
 				writestruct(wd, DATA, "RigidBodyOb", 1, ob->rigidbody_object);
 			}
-			
+			if (ob->rigidbody_constraint) {
+				writestruct(wd, DATA, "RigidBodyCon", 1, ob->rigidbody_constraint);
+			}
+
 			write_particlesystems(wd, &ob->particlesystem);
 			write_modifiers(wd, &ob->modifiers);
 		}