add sf_curve

src/surface/sf_curve.scad

@@ -0,0 +1,29 @@
+use <_impl/_sf_square_surfaces.scad>;
+use <sf_solidify.scad>;
+use <ptf/ptf_rotate.scad>;
+
+module sf_curve(levels, points, thickness, depth, invert = false) {
+    rows = len(levels);
+    columns = len(levels[0]);
+
+    normal_vts = [
+		for(i = [0:columns - 1]) 
+		let(v = points[i + 1] - points[i])
+		ptf_rotate(v / norm(v), [0, -90, 0])
+	];
+		
+	dp = is_undef(depth) ? thickness / 2 : depth;
+	surfaces = _sf_square_surfaces(levels, thickness, dp, invert);
+	
+    function _curve(s) = [
+		for(y = [0:rows - 1])
+		[
+			for(x = [0:columns - 1]) 
+			let(p = points[x])
+			[p[0], y, p[2]] + normal_vts[x] * s[y][x][2]
+		]
+	];
+
+	
+	sf_solidify(_curve(surfaces[0]), _curve(surfaces[1]));
+}