BGE #18665: Servo control and relative motion

Servo control motion actuator did not work as expected when the object
is moving on a moving platform. 

This patch introduces a new Ref field in the servo motion actuator
to set a reference object for the velocity calculation.
You can set the object during the game using the actuator "reference"
attribute; use an object name or an object reference.

The servo controller takes into account the angular velocity of the
reference object to compute the relative local velocity.

1 files changed, 17 insertions, 0 deletions

diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 91557da7aa6..0f233410f4e 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -3077,6 +3077,10 @@ static void lib_link_object(FileData *fd, Main *main)
 					bAddObjectActuator *eoa= act->data;
 					if(eoa) eoa->ob= newlibadr(fd, ob->id.lib, eoa->ob);
 				}
+				else if(act->type==ACT_OBJECT) {
+					bObjectActuator *oa= act->data;
+					oa->reference= newlibadr(fd, ob->id.lib, oa->reference);
+				}
 				else if(act->type==ACT_EDIT_OBJECT) {
 					bEditObjectActuator *eoa= act->data;
 					if(eoa==NULL) {
@@ -3087,6 +3091,15 @@ static void lib_link_object(FileData *fd, Main *main)
 						eoa->me= newlibadr(fd, ob->id.lib, eoa->me);
 					}
 				}
+				else if(act->type==ACT_OBJECT) {
+					bObjectActuator *oa= act->data;
+					if(oa==NULL) {
+						init_actuator(act);
+					}
+					else {
+						oa->reference= newlibadr(fd, ob->id.lib, oa->reference);
+					}
+				}
 				else if(act->type==ACT_SCENE) {
 					bSceneActuator *sa= act->data;
 					sa->camera= newlibadr(fd, ob->id.lib, sa->camera);
@@ -8862,6 +8875,10 @@ static void expand_object(FileData *fd, Main *mainvar, Object *ob)
 				expand_doit(fd, mainvar, eoa->me);
 			}
 		}
+		else if(act->type==ACT_OBJECT) {
+			bObjectActuator *oa= act->data;
+			expand_doit(fd, mainvar, oa->reference);
+		}
 		else if(act->type==ACT_SCENE) {
 			bSceneActuator *sa= act->data;
 			expand_doit(fd, mainvar, sa->camera);