add sf_cylinder

src/surface/sf_cylinder.scad

@@ -0,0 +1,30 @@
+use <../sweep.scad>;
+
+module sf_cylinder(levels, radius, thickness, depth, invert = false, convexity = 1) {
+    row_leng = len(levels[0]);
+    a_step = 360 / row_leng;
+    d_scale = (invert ? -depth : depth) / 255;
+    or = thickness + (invert ? radius + depth : radius - depth);
+    ir = radius;
+    row_range = [0:row_leng - 1];
+
+    sections = [
+        for(z = [0:len(levels) - 1]) 
+            concat(
+                [for(xi = row_range)
+                    let(
+                        r = or + levels[z][xi] * d_scale,
+                        a = xi * a_step
+                    )
+                    [r * cos(a), r * sin(a), -z + row_leng]
+                ],
+                [for(xi = row_range)
+                    let(a = xi * a_step)
+                    [ir * cos(a), ir * sin(a), -z + row_leng]
+                ]
+            )
+            
+    ];
+
+    sweep(sections,  "HOLLOW");
+}