add sf_torus

src/experimental/sf_torus.scad

@@ -0,0 +1,41 @@
+use <experimental/_impl/_sf_square_surfaces.scad>;
+use <experimental/sf_solidify.scad>;
+use <experimental/tf_torus.scad>;
+
+/*
+    levels : A list of numbers (0 ~ 255).
+    radius: torus [R, r]
+    thickness: shell thickness
+    angle: torus [A, a].
+    twist: The number of degrees of through which the rectangle is twisted.
+    invert: inverts how the gray levels are translated into height values.
+*/
+module sf_torus(levels, radius, thickness, angle = [360, 360], twist = 0, invert = false) {
+    surface = _sf_square_surfaces(levels, thickness, invert);
+    rows = len(levels);
+    columns = len(levels[0]);
+    size = [columns - 1, rows - 1];
+
+    R = radius[0];
+    r = radius[1];
+
+    offset_z = invert ? thickness : 0;
+
+    tr1 = [R, r + offset_z];
+    tr2 = [R + thickness, r];
+
+    sf_solidify(
+        [
+            for(row = surface[0]) 
+            [
+                for(p = row) tf_torus(size, p, tr1, angle, twist)
+            ]
+        ],
+        [
+            for(row = surface[1]) 
+            [
+                for(p = row) tf_torus(size, p, tr2, angle, twist)
+            ]
+        ]
+    );
+}