add hello world example and edit source tree

include/bounce/common/memory/stack_allocator.h

@@ -21,9 +21,9 @@
 
 #include <bounce/common/settings.h>
 
-// Allocate 10 MiB from the stack. 
+// Allocate 1 MiB from the stack. 
 // Increase as you want.
-const u32 b3_maxStackSize = B3_MiB(10);
+const u32 b3_maxStackSize = B3_MiB(1);
 
 // A stack allocator.
 class b3StackAllocator 

include/bounce/dynamics/body.h

@@ -116,6 +116,12 @@ public:
 	// However, manipulating a body transform during the simulation may cause non-physical behaviour.
 	void SetTransform(const b3Vec3& position, const b3Vec3& axis, float32 angle);
 	
+	// Get the position of the world body origin.
+	b3Vec3 GetPosition() const;
+
+	// Get the orientation of the world body frame.
+	b3Quat GetOrientation() const;
+
 	// Get the gravity scale of the body. One is used by default.
 	float32 GetGravityScale() const;
 	
@@ -382,6 +388,16 @@ inline void b3Body::SetTransform(const b3Vec3& position, const b3Vec3& axis, flo
 	SynchronizeShapes();
 }
 
+inline b3Vec3 b3Body::GetPosition() const
+{
+	return m_sweep.worldCenter;
+}
+
+inline b3Quat b3Body::GetOrientation() const
+{
+	return m_sweep.orientation;
+}
+
 inline b3Vec3 b3Body::GetLocalVector(const b3Vec3& vector) const
 {
 	return b3MulT(m_xf.rotation, vector);

include/bounce/dynamics/time_step.h

@@ -53,7 +53,7 @@ enum b3LimitState
 
 // Return the Steiner's matrix given the displacement vector from the old 
 // center of rotation to the new center of rotation.
-// The result equals to transpose( skew(v) ) * skew(v) or diagonal(v^2) - outer(v)
+// The result equals to transpose( skew(v) ) * skew(v) or diagonal(v^2) - outer(v, v)
 inline b3Mat33 b3Steiner(const b3Vec3& v)
 {
 	float32 xx = v.x * v.x;