add sf_thicken_tri

src/surface/sf_thicken_tri.scad

@@ -0,0 +1,123 @@
+use <../util/sort.scad>;
+use <../util/find_index.scad>;
+use <../util/slice.scad>;
+use <../util/sum.scad>;
+use <../surface/sf_solidify_tri.scad>;
+
+module sf_thicken_tri(points, triangles, thickness, direction = "BOTH") {
+	ascending = function(e1, e2) e1 - e2;
+
+	function connected_tris(leng_pts, triangles) =
+		let(
+			leng = len(triangles),
+			cnt_tris = [for(i = [0:leng_pts - 1]) []]
+		)
+		_connected_tris(triangles, leng, cnt_tris);
+		
+	function _connected_tris(triangles, leng, cnt_tris, i = 0) = 
+		i == leng ? cnt_tris :
+		let(
+			tri = sort(triangles[i], by = ascending),
+			b0 = cnt_tris[tri[0]],
+			b1 = cnt_tris[tri[1]],
+			b2 = cnt_tris[tri[2]],
+			nb0 = concat(b0, [triangles[i]]),
+			nb1 = concat(b1, [triangles[i]]),
+			nb2 = concat(b2, [triangles[i]]),
+			n_cnt_tris = concat(
+				slice(cnt_tris, 0, tri[0]),
+				[nb0],
+				slice(cnt_tris, tri[0] + 1, tri[1]),
+				[nb1],
+				slice(cnt_tris, tri[1] + 1, tri[2]),
+				[nb2],
+				slice(cnt_tris, tri[2] + 1)
+			)
+		)
+		_connected_tris(triangles, leng, n_cnt_tris, i + 1);
+
+	function tri_normal(tri) =
+		let(v = cross(tri[2] - tri[0], tri[1] - tri[0])) v / norm(v); 
+
+    leng_pts = len(points);
+    cnn_tris = connected_tris(leng_pts, triangles);
+
+    if(is_list(direction)) {
+        dir_v = direction / norm(direction);
+        mid = sort(points)[leng_pts / 2];
+        tri = cnn_tris[find_index(points, function(p) p == mid)][0];
+        nv = tri_normal([points[tri[0]], points[tri[1]], points[tri[2]]]);
+        pts = [for(p = points) p + dir_v * thickness];
+
+        if(nv * dir_v > 0) {
+            sf_solidify_tri(pts, points, triangles);
+        }
+        else {
+            sf_solidify_tri(points, pts, triangles);
+        }
+    }
+    else {
+        vertex_normals = [
+            for(i = [0:leng_pts - 1])
+            let(
+                normals = [
+                    for(tri = cnn_tris[i])
+                    tri_normal([
+                        points[tri[0]], 
+                        points[tri[1]], 
+                        points[tri[2]]]
+                    )
+                ]
+            )
+            sum(normals) / len(normals)
+        ];
+
+        if(direction == "BOTH") {
+            half_thickness = thickness / 2;
+            pts1 = points + vertex_normals * half_thickness;
+            pts2 = points - vertex_normals * half_thickness;
+            sf_solidify_tri(pts1, pts2, triangles);
+        }
+        else if(direction == "FORWARD") {
+            pts1 = points + vertex_normals * thickness;
+            pts2 = points;
+            sf_solidify_tri(pts1, pts2, triangles);
+        }
+        else {
+            pts1 = points;
+            pts2 = points - vertex_normals * thickness;
+            sf_solidify_tri(pts1, pts2, triangles);
+        }
+    }
+}
+
+/*
+
+use <triangle/tri_delaunay.scad>;
+use <triangle/tri_delaunay_indices.scad>;
+use <triangle/tri_delaunay_shapes.scad>;
+
+use <surface/sf_thicken_tri.scad>;
+
+points = [for(i = [0:50]) rands(-200, 200, 2)]; 
+
+delaunay = tri_delaunay(points, ret = "DELAUNAY");
+
+// count-clockwise (dotSCAD 2D polygon convention)
+indices = tri_delaunay_indices(delaunay);
+shapes = tri_delaunay_shapes(delaunay);
+
+for(tri = shapes) {
+    offset(-1)
+        polygon(tri);
+}
+
+// triangles: clockwise (openscad 3D face convention)
+triangles = [for(tri = indices) [tri[2], tri[1], tri[0]]];
+pts = [for(p = points) [p[0], p[1], rands(100, 120, 1)[0]]];
+thickness = 5;
+
+sf_thicken_tri(pts, triangles, thickness);
+
+
+*/