Add some description comments in the collision shapes

src/collision/shapes/BoxShape.cpp

@@ -30,7 +30,6 @@
 #include <cassert>
 
 using namespace reactphysics3d;
-using namespace std;
 
 // Constructor
 BoxShape::BoxShape(const Vector3& extent, decimal margin)

src/collision/shapes/BoxShape.h

@@ -40,7 +40,14 @@ namespace reactphysics3d {
  * This class represents a 3D box shape. Those axis are unit length.
  * The three extents are half-widths of the box along the three
  * axis x, y, z local axis. The "transform" of the corresponding
- * rigid body gives an orientation and a position to the box.
+ * rigid body will give an orientation and a position to the box. This
+ * collision shape uses an extra margin distance around it for collision
+ * detection purpose. The default margin is 4cm (if your units are meters,
+ * which is recommended). In case, you want to simulate small objects
+ * (smaller than the margin distance), you might want to reduce the margin by
+ * specifying your own margin distance using the "margin" parameter in the
+ * constructor of the box shape. Otherwise, it is recommended to use the
+ * default margin distance by not using the "margin" parameter in the constructor.
  */
 class BoxShape : public CollisionShape {
 

src/collision/shapes/ConeShape.h

@@ -40,7 +40,13 @@ namespace reactphysics3d {
  * by its height and by the radius of its base. The center of the
  * cone is at the half of the height. The "transform" of the
  * corresponding rigid body gives an orientation and a position
- * to the cone.
+ * to the cone. This collision shape uses an extra margin distance around
+ * it for collision detection purpose. The default margin is 4cm (if your
+ * units are meters, which is recommended). In case, you want to simulate small
+ * objects (smaller than the margin distance), you might want to reduce the margin
+ * by specifying your own margin distance using the "margin" parameter in the
+ * constructor of the cone shape. Otherwise, it is recommended to use the
+ * default margin distance by not using the "margin" parameter in the constructor.
  */
 class ConeShape : public CollisionShape {
 

src/collision/shapes/CylinderShape.h

@@ -40,6 +40,13 @@ namespace reactphysics3d {
  * and centered at the origin. The cylinder is defined by its height
  * and the radius of its base. The "transform" of the corresponding
  * rigid body gives an orientation and a position to the cylinder.
+ * This collision shape uses an extra margin distance around it for collision
+ * detection purpose. The default margin is 4cm (if your units are meters,
+ * which is recommended). In case, you want to simulate small objects
+ * (smaller than the margin distance), you might want to reduce the margin by
+ * specifying your own margin distance using the "margin" parameter in the
+ * constructor of the cylinder shape. Otherwise, it is recommended to use the
+ * default margin distance by not using the "margin" parameter in the constructor.
  */
 class CylinderShape : public CollisionShape {
 
@@ -111,7 +118,7 @@ inline decimal CylinderShape::getRadius() const {
 
 // Return the height
 inline decimal CylinderShape::getHeight() const {
-    return mHalfHeight * decimal(2.0);
+    return mHalfHeight + mHalfHeight;
 }
 
 // Return the number of bytes used by the collision shape

src/collision/shapes/SphereShape.cpp

@@ -29,7 +29,6 @@
 #include <cassert>
 
 using namespace reactphysics3d;
-using namespace std;
 
 // Constructor
 SphereShape::SphereShape(decimal radius) : CollisionShape(SPHERE, radius), mRadius(radius) {

src/collision/shapes/SphereShape.h

@@ -36,7 +36,10 @@ namespace reactphysics3d {
 // Class SphereShape
 /**
  * This class represents a sphere collision shape that is centered
- * at the origin and defined by its radius.
+ * at the origin and defined by its radius. This collision shape does not
+ * have an explicit object margin distance. The margin is implicitly the
+ * radius of the sphere. Therefore, no need to specify an object margin
+ * for a sphere shape.
  */
 class SphereShape : public CollisionShape {