BUlletSim: move safeynet ground plane to lower altitude. Define new BulletSim

parameter 'TerrainGroundPlane' which defaults to -500.

BulletSim had assumed altitudes never went negative but that is not true. The
ground plane is just a safety net so things wouldn't fall to infinity.

1 files changed, 3 insertions, 2 deletions

diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSTerrainManager.cs b/OpenSim/Region/Physics/BulletSPlugin/BSTerrainManager.cs
index 3013077..9067a2c 100755
--- a/OpenSim/Region/Physics/BulletSPlugin/BSTerrainManager.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSTerrainManager.cs
@@ -136,9 +136,10 @@ public sealed class BSTerrainManager : IDisposable
     {
         DetailLog("{0},BSTerrainManager.CreateInitialGroundPlaneAndTerrain,region={1}", BSScene.DetailLogZero, m_physicsScene.RegionName);
         // The ground plane is here to catch things that are trying to drop to negative infinity
-        BulletShape groundPlaneShape = m_physicsScene.PE.CreateGroundPlaneShape(BSScene.GROUNDPLANE_ID, 1f, BSParam.TerrainCollisionMargin);
+        BulletShape groundPlaneShape = m_physicsScene.PE.CreateGroundPlaneShape(BSScene.GROUNDPLANE_ID, 1f, BSParam.TerrainCollisionMargin);

+        Vector3 groundPlaneAltitude = new Vector3(0f, 0f, BSParam.TerrainGroundPlane);
         m_groundPlane = m_physicsScene.PE.CreateBodyWithDefaultMotionState(groundPlaneShape,
-                                        BSScene.GROUNDPLANE_ID, Vector3.Zero, Quaternion.Identity);
+                                        BSScene.GROUNDPLANE_ID, groundPlaneAltitude, Quaternion.Identity);
 
         // Everything collides with the ground plane.
         m_groundPlane.collisionType = CollisionType.Groundplane;