DebugTools: make it clearer that ForceRenderer takes a reference.

doc/snippets/MagnumDebugTools-gl.cpp

@@ -73,8 +73,9 @@ DebugTools::ResourceManager::instance().set("my",
         .setSize(5.0f)
         .setColor(Color3::fromHsv({120.0_degf, 1.0f, 0.7f})));
 
-// Create debug renderer for given object, use "my" options for it
-Vector3 force;
+Vector3 force; // taken as a reference, has to be kept in scope
+
+// Create debug renderer for given force, use "my" options for it
 new DebugTools::ForceRenderer3D(*object, {0.3f, 1.5f, -0.7f}, force, "my",
         &debugDrawables);
 /* [ForceRenderer] */

src/Magnum/DebugTools/ForceRenderer.h

@@ -103,7 +103,11 @@ See @ref debug-tools-renderers for more information.
 
 @section DebugTools-ForceRenderer-usage Basic usage
 
-Example code:
+Example code --- note that the @p force is saved as a reference to the original
+vector (so when you update it, the renderer updates itself as well), and thus
+it must be available for the whole lifetime of the renderer. The renderer is
+automatically added to object's features so you don't need to keep a reference
+to it.
 
 @snippet MagnumDebugTools-gl.cpp ForceRenderer
 
@@ -124,10 +128,6 @@ template<UnsignedInt dimensions> class MAGNUM_DEBUGTOOLS_EXPORT ForceRenderer: p
          *      @ref DebugTools-ForceRenderer-usage "class documentation" for
          *      more information.
          * @param drawables     Drawable group
-         *
-         * The renderer is automatically added to object's features, @p force
-         * is saved as reference to original vector and thus it must be
-         * available for the whole lifetime of the renderer.
          */
         explicit ForceRenderer(SceneGraph::AbstractObject<dimensions, Float>& object, const VectorTypeFor<dimensions, Float>& forcePosition, const VectorTypeFor<dimensions, Float>& force, ResourceKey options = ResourceKey(), SceneGraph::DrawableGroup<dimensions, Float>* drawables = nullptr);