null joint sample

samples/sample_joints.cpp

@@ -349,6 +349,59 @@ class MotorJoint : public Sample
 
 static int sampleMotorJoint = RegisterSample( "Joints", "Motor Joint", MotorJoint::Create );
 
+// This sample shows how to use a null joint to prevent collision between two bodies.
+// This is more specific than filters. It also shows that sleeping is coupled by the null joint.
+class NullJoint : public Sample
+{
+public:
+	explicit NullJoint( Settings& settings )
+		: Sample( settings )
+	{
+		if ( settings.restart == false )
+		{
+			g_camera.m_center = { 0.0f, 7.0f };
+			g_camera.m_zoom = 25.0f * 0.4f;
+		}
+
+		{
+			b2BodyId groundId;
+			b2BodyDef bodyDef = b2DefaultBodyDef();
+			groundId = b2CreateBody( m_worldId, &bodyDef );
+			b2ShapeDef shapeDef = b2DefaultShapeDef();
+			b2Segment segment = { { -20.0f, 0.0f }, { 20.0f, 0.0f } };
+			b2CreateSegmentShape( groundId, &shapeDef, &segment );
+		}
+
+		{
+			b2BodyDef bodyDef = b2DefaultBodyDef();
+			bodyDef.type = b2_dynamicBody;
+			bodyDef.position = { -4.0f, 2.0f };
+			b2BodyId bodyId1 = b2CreateBody( m_worldId, &bodyDef );
+
+			b2Polygon box = b2MakeSquare( 2.0f );
+			b2ShapeDef shapeDef = b2DefaultShapeDef();
+			b2CreatePolygonShape( bodyId1, &shapeDef, &box );
+
+			bodyDef.position = { 4.0f, 2.0f };
+			b2BodyId bodyId2 = b2CreateBody( m_worldId, &bodyDef );
+			b2CreatePolygonShape( bodyId2, &shapeDef, &box );
+
+			b2NullJointDef jointDef = b2DefaultNullJointDef();
+			jointDef.bodyIdA = bodyId1;
+			jointDef.bodyIdB = bodyId2;
+
+			b2CreateNullJoint( m_worldId, &jointDef );
+		}
+	}
+
+	static Sample* Create( Settings& settings )
+	{
+		return new NullJoint( settings );
+	}
+};
+
+static int sampleNullJoint = RegisterSample( "Joints", "Null Joint", NullJoint::Create );
+
 class RevoluteJoint : public Sample
 {
 public:

src/core.h

@@ -162,7 +162,7 @@ extern float b2_lengthUnitsPerMeter;
 // to move by a small amount without triggering a tree adjustment.
 // This is in meters.
 // @warning modifying this can have a significant impact on performance
-#define b2_aabbMargin ( 0.02f * b2_lengthUnitsPerMeter )
+#define b2_aabbMargin ( 0.1f * b2_lengthUnitsPerMeter )
 
 // todo testing
 #define b2_aabbVelocityScale 0.0f