BGE physics: When colliding, report first contact point to Python

This patch adds two parameters to the functions in the
collisionCallbacks list. The callback function should thus be like
this:

```
def on_colliding(other, point, normal):
    print("Colliding with %s at %s with normal %s" % (other, point, normal))

game_ob.collisionCallbacks.append(on_colliding)
```

The `point` parameter will contain the collision point in world
coordinates on the current object, and the `normal` contains the
surface normal at the collision point.

The callback functions are checked for the number of arguments
`co_argcount`. The new `point` and `normal` arguments are only passed
when `co_argcount > 1` or when `co_argcount` cannot be determined.

Reviewers: brita_, campbellbarton

Subscribers: sergey, sybren, agoose77

Projects: #game_physics

Differential Revision: https://developer.blender.org/D926

1 files changed, 17 insertions, 1 deletions

diff --git a/source/gameengine/Physics/Bullet/CcdPhysicsEnvironment.cpp b/source/gameengine/Physics/Bullet/CcdPhysicsEnvironment.cpp
index bcdc6f471ec..c43a3f782a7 100644
--- a/source/gameengine/Physics/Bullet/CcdPhysicsEnvironment.cpp
+++ b/source/gameengine/Physics/Bullet/CcdPhysicsEnvironment.cpp
@@ -2261,6 +2261,7 @@ void	CcdPhysicsEnvironment::CallbackTriggers()
 	int numManifolds = dispatcher->getNumManifolds();
 	for (int i=0;i<numManifolds;i++)
 	{
+		bool colliding_ctrl0 = true;
 		btPersistentManifold* manifold = dispatcher->getManifoldByIndexInternal(i);
 		int numContacts = manifold->getNumContacts();
 		if (!numContacts) continue;
@@ -2289,12 +2290,27 @@ void	CcdPhysicsEnvironment::CallbackTriggers()
 		if (iter == m_triggerControllers.end())
 		{
 			iter = m_triggerControllers.find(ctrl1);
+			colliding_ctrl0 = false;
 		}
 
 		if (iter != m_triggerControllers.end())
 		{
+			static PHY_CollData coll_data;
+			const btManifoldPoint &cp = manifold->getContactPoint(0);
+
+			/* Make sure that "point1" is always on the object we report on, and
+			 * "point2" on the other object. Also ensure the normal is oriented
+			 * correctly. */
+			btVector3 point1 = colliding_ctrl0 ? cp.m_positionWorldOnA : cp.m_positionWorldOnB;
+			btVector3 point2 = colliding_ctrl0 ? cp.m_positionWorldOnB : cp.m_positionWorldOnA;
+			btVector3 normal = colliding_ctrl0 ? -cp.m_normalWorldOnB : cp.m_normalWorldOnB;
+
+			coll_data.m_point1 = MT_Vector3(point1.m_floats);
+			coll_data.m_point2 = MT_Vector3(point2.m_floats);
+			coll_data.m_normal = MT_Vector3(normal.m_floats);
+
 			m_triggerCallbacks[PHY_OBJECT_RESPONSE](m_triggerCallbacksUserPtrs[PHY_OBJECT_RESPONSE],
-				ctrl0,ctrl1,0);
+				ctrl0, ctrl1, &coll_data);
 		}
 		// Bullet does not refresh the manifold contact point for object without contact response
 		// may need to remove this when a newer Bullet version is integrated