Different implementation of soft-landing.

lib/bullet/src/BulletDynamics/Vehicle/btWheelInfo.h

@@ -77,6 +77,8 @@ struct btWheelInfo
 	
 	bool m_bIsFrontWheel;
 	
+    bool m_was_on_ground;
+
 	void*		m_clientInfo;//can be used to store pointer to sync transforms...
 
 	btWheelInfo(btWheelInfoConstructionInfo& ci)
@@ -102,7 +104,7 @@ struct btWheelInfo
 		m_rollInfluence = btScalar(0.1);
 		m_bIsFrontWheel = ci.m_bIsFrontWheel;
 		m_maxSuspensionForce = ci.m_maxSuspensionForce;
-
+        m_was_on_ground = true;
 	}
 
 	void	updateWheel(const btRigidBody& chassis,RaycastInfo& raycastInfo);

src/physics/btKart.cpp

@@ -260,18 +260,15 @@ btScalar btKart::rayCast(unsigned int index)
     depth = raylen * rayResults.m_distFraction;
     if (object &&  depth < max_susp_len)
     {
-        param = rayResults.m_distFraction;
         wheel.m_raycastInfo.m_contactNormalWS  = rayResults.m_hitNormalInWorld;
         wheel.m_raycastInfo.m_contactNormalWS.normalize();
         wheel.m_raycastInfo.m_isInContact = true;
         ///@todo for driving on dynamic/movable objects!;
         wheel.m_raycastInfo.m_groundObject = &getFixedBody();
 
-        btScalar hitDistance = param*raylen;
+        wheel.m_raycastInfo.m_suspensionLength = depth - wheel.m_wheelsRadius;
-        wheel.m_raycastInfo.m_suspensionLength =
-            hitDistance - wheel.m_wheelsRadius;
-        //clamp on max suspension travel
 
+        //clamp on max suspension travel
         btScalar minSuspensionLength = wheel.getSuspensionRestLength()
                                 - wheel.m_maxSuspensionTravelCm*btScalar(0.01);
         btScalar maxSuspensionLength = wheel.getSuspensionRestLength()
@@ -314,35 +311,6 @@ btScalar btKart::rayCast(unsigned int index)
 
     } else
     {
-        // The raycast either hit nothing (object=NULL), or it hit something,
-        // but not in the maximum suspension range. If it hit something,
-        // check for the need of cushioning:
-        if(object)
-        {
-            // If the raycast hit something, see if the jump needs cushioning:
-            // i.e. a slowdown in fall speed in order to avoid that on landing
-            // the chassis hits the ground (causing a severe slowdown of the
-            // kart). The cushioning is done if the fall distance (v_down * dt)
-            // in this physics step is large enough that the kart would hit the
-            // ground, i.e. the maximum suspension length plus fall distance
-            // is larger than the distance to the object that was just detected.
-
-            // To allow for wall driving, properly project the velocity
-            // onto the normal
-            btVector3 v = m_chassisBody->getLinearVelocity();
-            btVector3 down(0, 1, 0);
-            btVector3 v_down = (v * down) * down;
-
-            if(depth < max_susp_len + v_down.length() *1./60.f)
-            {
-                // Apply an impulse that will roughly half the speed. Since
-                // there are 4 wheels, a single wheel should apply 1/4 of
-                // the necessary impulse:
-                btVector3 impulse = (-0.25f*0.5f/m_chassisBody->getInvMass())
-                                  * v_down;
-                m_chassisBody->applyCentralImpulse(impulse);
-            }
-        }
         depth = btScalar(-1.0);
         //put wheel info as in rest position
         wheel.m_raycastInfo.m_suspensionLength = wheel.getSuspensionRestLength();
@@ -422,6 +390,32 @@ void btKart::updateVehicle( btScalar step )
             m_num_wheels_on_ground++;
     }
 
+    bool needs_cushioning_test = false;
+    for(int i=0; i<m_wheelInfo.size(); i++)
+    {
+        btWheelInfo &wheel = m_wheelInfo[i];
+        if(!wheel.m_was_on_ground && wheel.m_raycastInfo.m_isInContact)
+        {
+            needs_cushioning_test = true;
+            break;
+        }
+    }
+    if(needs_cushioning_test)
+    {
+        const btVector3 &v = m_chassisBody->getLinearVelocity();
+        btVector3 down(0, 1, 0);
+        btVector3 v_down = (v * down) * down;
+        btScalar max_compensate_speed = m_wheelInfo[0].m_maxSuspensionForce * m_chassisBody->getInvMass() * step *4;
+        if(-v_down.getY() > max_compensate_speed)
+        {
+            btVector3 impulse = down * (-v_down.getY() - max_compensate_speed) / m_chassisBody->getInvMass();
+            Log::verbose("physics", "Cushioning %f", impulse.getY());
+            m_chassisBody->applyCentralImpulse(impulse);
+        }
+    }
+    for(int i=0; i<m_wheelInfo.size(); i++)
+        m_wheelInfo[i].m_was_on_ground = m_wheelInfo[i].m_raycastInfo.m_isInContact;
+
     // If the kart is flying, try to keep it parallel to the ground.
     if(m_num_wheels_on_ground==0)
     {