diff --git a/geometry.scad b/geometry.scad
index 7cda463..561e6a2 100644
--- a/geometry.scad
+++ b/geometry.scad
@@ -1003,10 +1003,10 @@ function plane_point_nearest_origin(plane) =
 // Description:
 //   Given a plane as [A,B,C,D] where the cartesian equation for that plane
 //   is Ax+By+Cz=D, determines how far from that plane the given point is.
-//   The returned distance will be positive if the point is in front of the
-//   plane; on the same side of the plane as the normal of that plane points
-//   towards.  If the point is behind the plane, then the distance returned
-//   will be negative.  The normal of the plane is the same as [A,B,C].
+//   The returned distance will be positive if the point is above the
+//   plane, meaning on the side where the plane normal points.  
+//   If the point is below the plane, then the distance returned
+//   will be negative.  The normal of the plane is [A,B,C].
 // Arguments:
 //   plane = The `[A,B,C,D]` plane definition where `Ax+By+Cz=D` is the formula of the plane.
 //   point = The distance evaluation point.
@@ -1049,7 +1049,7 @@ function normalize_plane(plane) =
 // Topics: Geometry, Planes, Lines, Angle
 // Description:
 //   Compute the angle between a plane [A, B, C, D] and a 3d line, specified as a pair of 3d points [p1,p2].
-//   The resulting angle is signed, with the sign positive if the vector p2-p1 lies on
+//   The resulting angle is signed, with the sign positive if the vector p2-p1 lies above the plane, on
 //   the same side of the plane as the plane's normal vector.
 function plane_line_angle(plane, line) =
     assert( _valid_plane(plane), "Invalid plane." )
@@ -1226,7 +1226,7 @@ function points_on_plane(points, plane, eps=EPSILON) =
     _pointlist_greatest_distance(points,plane) < eps;
 
 
-// Function: in_front_of_plane()
+// Function: above_plane()
 // Usage:
 //   test = in_front_of_plane(plane, point);
 // Topics: Geometry, Planes
@@ -1238,7 +1238,7 @@ function points_on_plane(points, plane, eps=EPSILON) =
 // Arguments:
 //   plane = The [A,B,C,D] coefficients for the first plane equation `Ax+By+Cz=D`.
 //   point = The 3D point to test.
-function in_front_of_plane(plane, point) =
+function above_plane(plane, point) =
     point_plane_distance(plane, point) > EPSILON;
 
 
diff --git a/hull.scad b/hull.scad
index 4adb7c3..8371021 100644
--- a/hull.scad
+++ b/hull.scad
@@ -186,7 +186,7 @@ function hull3d_faces(points) =
         remaining = [for (i = [0:1:len(points)-1]) if (i!=a && i!=b && i!=c && i!=d) i],
         // Build an initial tetrahedron.
         // Swap b, c if d is in front of triangle t.
-        ifop = in_front_of_plane(plane, points[d]),
+        ifop = above_plane(plane, points[d]),
         bc = ifop? [c,b] : [b,c],
         b = bc[0],
         c = bc[1],
diff --git a/tests/test_geometry.scad b/tests/test_geometry.scad
index 2c19e6d..ae124fe 100644
--- a/tests/test_geometry.scad
+++ b/tests/test_geometry.scad
@@ -51,7 +51,7 @@ test_polygon_line_intersection();
 test_plane_intersection();
 test_coplanar();
 test_points_on_plane();
-test_in_front_of_plane();
+test_above_plane();
 test_circle_2tangents();
 test_circle_3points();
 test_circle_point_tangents();
@@ -754,17 +754,17 @@ module test_coplanar() {
 *test_coplanar();
 
 
-module test_in_front_of_plane() {
+module test_above_plane() {
     plane = plane3pt([0,0,0], [0,10,10], [10,0,10]);
-    assert(in_front_of_plane(plane, [5,5,10]) == false);
-    assert(in_front_of_plane(plane, [-5,0,0]) == true);
-    assert(in_front_of_plane(plane, [5,0,0]) == false);
-    assert(in_front_of_plane(plane, [0,-5,0]) == true);
-    assert(in_front_of_plane(plane, [0,5,0]) == false);
-    assert(in_front_of_plane(plane, [0,0,5]) == true);
-    assert(in_front_of_plane(plane, [0,0,-5]) == false);
+    assert(above_plane(plane, [5,5,10]) == false);
+    assert(above_plane(plane, [-5,0,0]) == true);
+    assert(above_plane(plane, [5,0,0]) == false);
+    assert(above_plane(plane, [0,-5,0]) == true);
+    assert(above_plane(plane, [0,5,0]) == false);
+    assert(above_plane(plane, [0,0,5]) == true);
+    assert(above_plane(plane, [0,0,-5]) == false);
 }
-*test_in_front_of_plane();
+*test_above_plane();
 
 
 module test_is_path() {
@@ -808,7 +808,7 @@ module test_polygon_area() {
     assert(approx(polygon_area(circle(r=50,$fn=1000),signed=true), -PI*50*50, eps=0.1));
     assert(approx(polygon_area(rot([13,27,75],
                                p=path3d(circle(r=50,$fn=1000),fill=23)),
-                               signed=true), -PI*50*50, eps=0.1));
+                               signed=true), PI*50*50, eps=0.1));
     assert(abs(triangle_area([0,0], [0,10], [10,0]) + 50) < EPSILON);
     assert(abs(triangle_area([0,0], [0,10], [0,15])) < EPSILON);
     assert(abs(triangle_area([0,0], [10,0], [0,10]) - 50) < EPSILON);