diff --git a/include/selectable.h b/include/selectable.h
index fa63d447..08dd0c92 100644
--- a/include/selectable.h
+++ b/include/selectable.h
@@ -299,8 +299,8 @@ STRING_CONSTANT( Name, "PlaneSelectable" );
 virtual void selectPlanes( Selector& selector, SelectionTest& test, const PlaneCallback& selectedPlaneCallback ) = 0;
 virtual void selectReversedPlanes( Selector& selector, const SelectedPlanes& selectedPlanes ) = 0;
 
-virtual void bestPlaneDirect( SelectionTest& test, Plane3& plane, SelectionIntersection& intersection ) = 0;
-virtual void bestPlaneIndirect( SelectionTest& test, Plane3& plane, Vector3& intersection, float& dist ) = 0;
+virtual void bestPlaneDirect( SelectionTest& test, Plane3& plane, SelectionIntersection& intersection ) const = 0;
+virtual void bestPlaneIndirect( SelectionTest& test, Plane3& plane, Vector3& intersection, float& dist ) const = 0;
 virtual void selectByPlane( const Plane3& plane ) = 0;
 virtual void gatherPolygonsByPlane( const Plane3& plane, std::vector<std::vector<Vector3>>& polygons ) const = 0;
 };
diff --git a/libs/dragplanes.h b/libs/dragplanes.h
index dc00413f..a3eeb1f9 100644
--- a/libs/dragplanes.h
+++ b/libs/dragplanes.h
@@ -86,7 +86,7 @@ class DragPlanes
 {
 ObservedSelectable m_selectables[6];
 public:
-AABB m_bounds;
+mutable AABB m_bounds;
 DragPlanes( const SelectionChangeCallback& onchanged ) : m_selectables{ ObservedSelectable( onchanged ),
 																		ObservedSelectable( onchanged ),
 																		ObservedSelectable( onchanged ),
@@ -163,7 +163,7 @@ void selectReversedPlanes( const AABB& aabb, Selector& selector, const SelectedP
 			Selector_add( selector, m_selectables[i] );
 }
 
-void bestPlaneDirect( const AABB& aabb, SelectionTest& test, Plane3& plane, SelectionIntersection& intersection, const Matrix4& rotation = g_matrix4_identity ){
+void bestPlaneDirect( const AABB& aabb, SelectionTest& test, Plane3& plane, SelectionIntersection& intersection, const Matrix4& rotation = g_matrix4_identity ) const {
 	AABB aabb_ = aabb;
 	for( std::size_t i = 0; i < 3; ++i ) /* make sides of flat patches more selectable */
 		if( aabb_.extents[i] < 1 )
@@ -195,7 +195,7 @@ void bestPlaneDirect( const AABB& aabb, SelectionTest& test, Plane3& plane, Sele
 	}
 	m_bounds = aabb;
 }
-void bestPlaneIndirect( const AABB& aabb, SelectionTest& test, Plane3& plane, Vector3& intersection, float& dist, const Matrix4& rotation = g_matrix4_identity ){
+void bestPlaneIndirect( const AABB& aabb, SelectionTest& test, Plane3& plane, Vector3& intersection, float& dist, const Matrix4& rotation = g_matrix4_identity ) const {
 	Vector3 corners[8];
 	aabb_corners_oriented( aabb, rotation, corners );
 
diff --git a/plugins/entity/light.cpp b/plugins/entity/light.cpp
index d11d6116..99094f05 100644
--- a/plugins/entity/light.cpp
+++ b/plugins/entity/light.cpp
@@ -1874,13 +1874,13 @@ void selectReversedPlanes( Selector& selector, const SelectedPlanes& selectedPla
 	}
 }
 
-void bestPlaneDirect( SelectionTest& test, Plane3& plane, SelectionIntersection& intersection ){
+void bestPlaneDirect( SelectionTest& test, Plane3& plane, SelectionIntersection& intersection ) const {
 	if ( g_lightType == LIGHTTYPE_DOOM3 ) {
 		test.BeginMesh( localToWorld() );
 		m_dragPlanes.bestPlaneDirect( m_contained.aabb(), test, plane, intersection, rotation() );
 	}
 }
-void bestPlaneIndirect( SelectionTest& test, Plane3& plane, Vector3& intersection, float& dist ){
+void bestPlaneIndirect( SelectionTest& test, Plane3& plane, Vector3& intersection, float& dist ) const {
 	if ( g_lightType == LIGHTTYPE_DOOM3 ) {
 		test.BeginMesh( localToWorld() );
 		m_dragPlanes.bestPlaneIndirect( m_contained.aabb(), test, plane, intersection, dist, rotation() );
diff --git a/radiant/brush.h b/radiant/brush.h
index 6b5e3cbe..cf3ff39b 100644
--- a/radiant/brush.h
+++ b/radiant/brush.h
@@ -3930,24 +3930,24 @@ void selectReversedPlanes( Selector& selector, const SelectedPlanes& selectedPla
 	}
 }
 
-void bestPlaneDirect( SelectionTest& test, Plane3& plane, SelectionIntersection& intersection ){
+void bestPlaneDirect( SelectionTest& test, Plane3& plane, SelectionIntersection& intersection ) const {
 	test.BeginMesh( localToWorld() );
-	for ( FaceInstances::iterator i = m_faceInstances.begin(); i != m_faceInstances.end(); ++i )
+	for ( const FaceInstance& fi : m_faceInstances )
 	{
 		SelectionIntersection intersection_new;
-		( *i ).testSelect( test, intersection_new );
+		fi.testSelect( test, intersection_new );
 		if( SelectionIntersection_closer( intersection_new, intersection ) ){
 			intersection = intersection_new;
-			plane = ( *i ).getFace().plane3();
+			plane = fi.getFace().plane3();
 		}
 	}
 }
-void bestPlaneIndirect( SelectionTest& test, Plane3& plane, Vector3& intersection, float& dist ){
+void bestPlaneIndirect( SelectionTest& test, Plane3& plane, Vector3& intersection, float& dist ) const {
 	test.BeginMesh( localToWorld() );
 	float dot = 1;
-	for ( EdgeInstances::iterator i = m_edgeInstances.begin(); i != m_edgeInstances.end(); ++i )
+	for ( const EdgeInstance& ei : m_edgeInstances )
 	{
-		( *i ).bestPlaneIndirect( test, plane, intersection, dist, dot );
+		ei.bestPlaneIndirect( test, plane, intersection, dist, dot );
 	}
 }
 void selectByPlane( const Plane3& plane ){
diff --git a/radiant/patch.h b/radiant/patch.h
index 1b2ca3af..b0c8ce56 100644
--- a/radiant/patch.h
+++ b/radiant/patch.h
@@ -1649,11 +1649,11 @@ void selectReversedPlanes( Selector& selector, const SelectedPlanes& selectedPla
 	m_dragPlanes.selectReversedPlanes( m_patch.localAABB(), selector, selectedPlanes );
 }
 
-void bestPlaneDirect( SelectionTest& test, Plane3& plane, SelectionIntersection& intersection ){
+void bestPlaneDirect( SelectionTest& test, Plane3& plane, SelectionIntersection& intersection ) const {
 	test.BeginMesh( localToWorld() );
 	m_dragPlanes.bestPlaneDirect( m_patch.localAABB(), test, plane, intersection );
 }
-void bestPlaneIndirect( SelectionTest& test, Plane3& plane, Vector3& intersection, float& dist ){
+void bestPlaneIndirect( SelectionTest& test, Plane3& plane, Vector3& intersection, float& dist ) const {
 	test.BeginMesh( localToWorld() );
 	m_dragPlanes.bestPlaneIndirect( m_patch.localAABB(), test, plane, intersection, dist );
 }