accept constraint with single rigidbody

Demos/ColladaDemo/ColladaConverter.cpp

@@ -537,8 +537,8 @@ void	ColladaConverter::prepareConstraints(ConstraintInput& input)
 					const domRigid_constraint::domRef_attachmentRef attachRefBody = rigidConstraintRef->getRef_attachment();
 					const domRigid_constraint::domAttachmentRef attachBody1 = rigidConstraintRef->getAttachment();
 
-					daeString orgUri0 = attachRefBody->getRigid_body().getOriginalURI();
+					daeString orgUri0 = attachRefBody ? attachRefBody->getRigid_body().getOriginalURI() : "";
-					daeString orgUri1 = attachBody1->getRigid_body().getOriginalURI();
+					daeString orgUri1 = attachBody1 ? attachBody1->getRigid_body().getOriginalURI() : "";
 					btRigidBody* body0=0,*body1=0;
 					
 					for (int i=0;i<m_numObjects;i++)
@@ -579,14 +579,22 @@ void	ColladaConverter::prepareConstraints(ConstraintInput& input)
 					{
 						
 						btTransform attachFrameRef0;
+						attachFrameRef0.setIdentity();
+
+						if (attachRefBody)
+						{
 							attachFrameRef0 = 
 								GetbtTransformFromCOLLADA_DOM
 								(
 								emptyMatrixArray,
 								attachRefBody->getRotate_array(),
 								attachRefBody->getTranslate_array());
+						}
 
 						btTransform attachFrameOther;
+						attachFrameOther.setIdentity();
+						if (attachBody1)
+						{
 							attachFrameOther =
 								GetbtTransformFromCOLLADA_DOM
 								(
@@ -594,6 +602,7 @@ void	ColladaConverter::prepareConstraints(ConstraintInput& input)
 								attachBody1->getRotate_array(),
 								attachBody1->getTranslate_array()
 								);
+						}
 
 
 						//convert INF / -INF into lower > upper
@@ -639,7 +648,22 @@ void	ColladaConverter::prepareConstraints(ConstraintInput& input)
 						}
 
 
-						if (body0&& body1)
+						if (body0 || body1)
+						{
+							//swap so that first body is non-zero
+							if (!body0)
+							{
+								createUniversalD6Constraint(
+								body1,
+								body0,
+								attachFrameOther,
+								attachFrameRef0,
+								linearLowerLimits,
+								linearUpperLimits,
+								angularLowerLimits,
+								angularUpperLimits
+									);
+							} else
 							{
 								createUniversalD6Constraint(
 								body0,
@@ -651,6 +675,7 @@ void	ColladaConverter::prepareConstraints(ConstraintInput& input)
 								angularLowerLimits,
 								angularUpperLimits
 									);
+							}
 						} else
 						{
 							printf("Error: Cannot find Rigidbodies(%s,%s) for constraint %s\n",orgUri0,orgUri1,constraintName);

Demos/ColladaDemo/ColladaDemo.cpp

@@ -57,8 +57,17 @@ class MyColladaConverter : public ColladaConverter
 			const btVector3& angularMaxLimits
 			)
 		{
-			if (bodyRef && bodyOther)
+			if (bodyRef)
 			{
+				if (!bodyOther)
+				{
+					 bodyOther = new btRigidBody(0,0,0);
+
+					 bodyOther->setWorldTransform(bodyRef->getWorldTransform());
+					 localAttachmentOther = localAttachmentFrameRef;
+
+				}
+
 				btGeneric6DofConstraint* genericConstraint = new btGeneric6DofConstraint(
 							*bodyRef,*bodyOther,
 							localAttachmentFrameRef,localAttachmentOther);