Add soft body anchor 'm_influence' to control the solver.

Thanks to Gregory Jaegy, see Issue 502
Avoid using btTransform to update btSoftBody (bounds are already in worldspace)
Use btConvexHullComputer for soft body cluster debug rendering
Fix soft body demo issue of invisible soft bodies (rendering was not enabled properly)

Demos/SoftDemo/SoftDemo.cpp

@@ -1484,8 +1484,20 @@ void	SoftDemo::renderme()
 	btIDebugDraw*	idraw=m_dynamicsWorld->getDebugDrawer();
 
 	glDisable(GL_TEXTURE_2D);
+	glDisable(GL_LIGHTING);
 	m_dynamicsWorld->debugDrawWorld();
 
+	btSoftRigidDynamicsWorld* softWorld = (btSoftRigidDynamicsWorld*)m_dynamicsWorld;
+	for (  int i=0;i<softWorld->getSoftBodyArray().size();i++)
+	{
+		btSoftBody*	psb=(btSoftBody*)softWorld->getSoftBodyArray()[i];
+		if (softWorld->getDebugDrawer() && !softWorld->getDebugDrawer()->getDebugMode() & (btIDebugDraw::DBG_DrawWireframe))
+		{
+			btSoftBodyHelpers::DrawFrame(psb,softWorld->getDebugDrawer());
+			btSoftBodyHelpers::Draw(psb,softWorld->getDebugDrawer(),softWorld->getDrawFlags());
+		}
+	}
+
 	/* Bodies		*/ 
 	btVector3	ps(0,0,0);
 	int			nps=0;

src/BulletSoftBody/btSoftBody.cpp

@@ -357,14 +357,14 @@ void			btSoftBody::appendTetra(int node0,
 
 //
 
-void			btSoftBody::appendAnchor(int node,btRigidBody* body, bool disableCollisionBetweenLinkedBodies)
+void			btSoftBody::appendAnchor(int node,btRigidBody* body, bool disableCollisionBetweenLinkedBodies,btScalar influence)
 {
 	btVector3 local = body->getWorldTransform().inverse()*m_nodes[node].m_x;
-	appendAnchor(node,body,local,disableCollisionBetweenLinkedBodies);
+	appendAnchor(node,body,local,disableCollisionBetweenLinkedBodies,influence);
 }
 
 //
-void			btSoftBody::appendAnchor(int node,btRigidBody* body, const btVector3& localPivot,bool disableCollisionBetweenLinkedBodies)
+void			btSoftBody::appendAnchor(int node,btRigidBody* body, const btVector3& localPivot,bool disableCollisionBetweenLinkedBodies,btScalar influence)
 {
 	if (disableCollisionBetweenLinkedBodies)
 	{
@@ -379,6 +379,7 @@ void			btSoftBody::appendAnchor(int node,btRigidBody* body, const btVector3& loc
 	a.m_body			=	body;
 	a.m_local			=	localPivot;
 	a.m_node->m_battach	=	1;
+	a.m_influence = influence;
 	m_anchors.push_back(a);
 }
 
@@ -2765,7 +2766,7 @@ void				btSoftBody::PSolve_Anchors(btSoftBody* psb,btScalar kst,btScalar ti)
 		const btVector3		va=a.m_body->getVelocityInLocalPoint(a.m_c1)*dt;
 		const btVector3		vb=n.m_x-n.m_q;
 		const btVector3		vr=(va-vb)+(wa-n.m_x)*kAHR;
-		const btVector3		impulse=a.m_c0*vr;
+		const btVector3		impulse=a.m_c0*vr*a.m_influence;
 		n.m_x+=impulse*a.m_c2;
 		a.m_body->applyImpulse(-impulse,a.m_c1);
 	}

src/BulletSoftBody/btSoftBody.h

@@ -282,6 +282,7 @@ public:
 		Node*					m_node;			// Node pointer
 		btVector3				m_local;		// Anchor position in body space
 		btRigidBody*			m_body;			// Body
+		btScalar				m_influence;
 		btMatrix3x3				m_c0;			// Impulse matrix
 		btVector3				m_c1;			// Relative anchor
 		btScalar				m_c2;			// ima*dt
@@ -752,8 +753,8 @@ public:
 
 	/* Append anchor														*/ 
 	void				appendAnchor(	int node,
-		btRigidBody* body, bool disableCollisionBetweenLinkedBodies=false);
+		btRigidBody* body, bool disableCollisionBetweenLinkedBodies=false,btScalar influence = 1);
-	void			appendAnchor(int node,btRigidBody* body, const btVector3& localPivot,bool disableCollisionBetweenLinkedBodies=false);
+	void			appendAnchor(int node,btRigidBody* body, const btVector3& localPivot,bool disableCollisionBetweenLinkedBodies=false,btScalar influence = 1);
 	/* Append linear joint													*/ 
 	void				appendLinearJoint(const LJoint::Specs& specs,Cluster* body0,Body body1);
 	void				appendLinearJoint(const LJoint::Specs& specs,Body body=Body());

src/BulletSoftBody/btSoftBodyHelpers.cpp

@@ -19,6 +19,8 @@ subject to the following restrictions:
 #include <string.h>
 #include "btSoftBodyHelpers.h"
 #include "LinearMath/btConvexHull.h"
+#include "LinearMath/btConvexHullComputer.h"
+
 
 //
 static void				drawVertex(	btIDebugDraw* idraw,
@@ -183,6 +185,35 @@ void			btSoftBodyHelpers::Draw(	btSoftBody* psb,
 				{				
 					vertices[j]=psb->m_clusters[i]->m_nodes[j]->m_x;
 				}
+#define USE_NEW_CONVEX_HULL_COMPUTER
+#ifdef USE_NEW_CONVEX_HULL_COMPUTER
+				btConvexHullComputer	computer;
+				int stride = sizeof(btVector3);
+				int count = vertices.size();
+				btScalar shrink=0.f;
+				btScalar shrinkClamp=0.f;
+				computer.compute(&vertices[0].getX(),stride,count,shrink,shrinkClamp);
+				for (int i=0;i<computer.faces.size();i++)
+				{
+
+					int face = computer.faces[i];
+					//printf("face=%d\n",face);
+					const btConvexHullComputer::Edge*  firstEdge = &computer.edges[face];
+					const btConvexHullComputer::Edge*  edge = firstEdge->getNextEdgeOfFace();
+
+					int v0 = firstEdge->getSourceVertex();
+					int v1 = firstEdge->getTargetVertex();
+					while (edge!=firstEdge)
+					{
+						int v2 = edge->getTargetVertex();
+						idraw->drawTriangle(computer.vertices[v0],computer.vertices[v1],computer.vertices[v2],color,1);
+						edge = edge->getNextEdgeOfFace();
+						v0=v1;
+						v1=v2;
+					};
+				}
+#else
+
 				HullDesc		hdsc(QF_TRIANGLES,vertices.size(),&vertices[0]);
 				HullResult		hres;
 				HullLibrary		hlib;
@@ -201,6 +232,8 @@ void			btSoftBodyHelpers::Draw(	btSoftBody* psb,
 						color,1);
 				}
 				hlib.ReleaseResult(hres);
+#endif
+
 			}
 			/* Velocities	*/ 
 #if 0

src/BulletSoftBody/btSoftBodyInternals.h

@@ -70,23 +70,9 @@ public:
 	///getAabb returns the axis aligned bounding box in the coordinate frame of the given transform t.
 	virtual void getAabb(const btTransform& t,btVector3& aabbMin,btVector3& aabbMax) const
 	{
-		/* t should be identity, but better be safe than...fast? */ 
+		/* t should be identity */ 
-		const btVector3	mins=m_body->m_bounds[0];
+		aabbMin=m_body->m_bounds[0];
-		const btVector3	maxs=m_body->m_bounds[1];
+		aabbMax=m_body->m_bounds[1];
-		const btVector3	crns[]={t*btVector3(mins.x(),mins.y(),mins.z()),
-			t*btVector3(maxs.x(),mins.y(),mins.z()),
-			t*btVector3(maxs.x(),maxs.y(),mins.z()),
-			t*btVector3(mins.x(),maxs.y(),mins.z()),
-			t*btVector3(mins.x(),mins.y(),maxs.z()),
-			t*btVector3(maxs.x(),mins.y(),maxs.z()),
-			t*btVector3(maxs.x(),maxs.y(),maxs.z()),
-			t*btVector3(mins.x(),maxs.y(),maxs.z())};
-		aabbMin=aabbMax=crns[0];
-		for(int i=1;i<8;++i)
-		{
-			aabbMin.setMin(crns[i]);
-			aabbMax.setMax(crns[i]);
-		}
 	}