triangle_area2d() -> triangle_area(). Added polygon_area()

geometry.scad

@@ -207,17 +207,17 @@ function find_circle_2tangents(pt1, pt2, pt3, r=undef, d=undef) =
 	) [cp, n];
 
 
-// Function: triangle_area2d()
+// Function: triangle_area()
 // Usage:
-//   triangle_area2d(a,b,c);
+//   triangle_area(a,b,c);
 // Description:
-//   Returns the area of a triangle formed between three vertices.
-//   Result will be negative if the points are in clockwise order.
+//   Returns the area of a triangle formed between three 2D or 3D vertices.
+//   Result will be negative if the points are 2D and in in clockwise order.
 // Examples:
-//   triangle_area2d([0,0], [5,10], [10,0]);  // Returns -50
-//   triangle_area2d([10,0], [5,10], [0,0]);  // Returns 50
-function triangle_area2d(a,b,c) =
-	(
+//   triangle_area([0,0], [5,10], [10,0]);  // Returns -50
+//   triangle_area([10,0], [5,10], [0,0]);  // Returns 50
+function triangle_area(a,b,c) =
+	len(a)==3? 0.5*norm(cross(c-a,c-b)) : (
 		a.x * (b.y - c.y) +
 		b.x * (c.y - a.y) +
 		c.x * (a.y - b.y)
@@ -376,6 +376,15 @@ function path_subselect(path,s1,u1,s2,u2) =
 	) pathout;
 
 
+// Function: polygon_area()
+// Usage:
+//   area = polygon_area(vertices);
+// Description:
+//   Given a polygon, returns the area of that polygon.  If the polygon is self-crossing, the results are undefined.
+function polygon_area(vertices) =
+	0.5*sum([for(i=[0:len(vertices)-1]) det2(select(vertices,i,i+1))]);
+
+
 // Function: assemble_path_fragments()
 // Usage:
 //   assemble_path_fragments(subpaths);

hull.scad

@@ -91,7 +91,7 @@ function hull2d_path(points) =
 		c = _find_first_noncollinear([a,b], points, 2)
 	) (c == len(points))? _hull2d_collinear(points) : let(
 		remaining = [ for (i = [2:1:len(points)-1]) if (i != c) i ],
-		ccw = triangle_area2d(points[a], points[b], points[c]) > 0,
+		ccw = triangle_area(points[a], points[b], points[c]) > 0,
 		polygon = ccw? [a,b,c] : [a,c,b]
 	) _hull2d_iterative(points, polygon, remaining);
 
@@ -131,7 +131,7 @@ function _find_conflicting_segments(points, polygon, point) = [
 		j = (i+1) % len(polygon),
 		p1 = points[polygon[i]],
 		p2 = points[polygon[j]],
-		area = triangle_area2d(p1, p2, point)
+		area = triangle_area(p1, p2, point)
 	) if (area < 0) i
 ];