add tri_ear_clipping

src/experimental/_impl/_tri_ear_clipping_impl.scad

@@ -0,0 +1,92 @@
+function _triangulate_in_triangle(p0, p1, p2, p) =
+    let(
+        v0 = p0 - p,
+        v1 = p1 - p,
+        v2 = p2 - p,
+        c0 = cross(v0, v1),
+        c1 = cross(v1, v2),
+        c2 = cross(v2, v0)
+    )
+    (c0 > 0 && c1 > 0 && c2 > 0) || (c0 < 0 && c1 < 0 && c2 < 0);
+
+function _triangulate_snipable(shape_pts, u, v, w, n, indices, epsilon = 0.0001) =
+    let(
+        a = shape_pts[indices[u]],
+        b = shape_pts[indices[v]],
+        c = shape_pts[indices[w]],
+        ax = a[0],
+        ay = a[1],
+        bx = b[0],
+        by = b[1],
+        cx = c[0],
+        cy = c[1],
+        determinant = cross([bx - ax, by - ay],  [cx - ax, cy - ay])
+    )
+    epsilon > determinant ? 
+        false : _triangulate_snipable_sub(shape_pts, n, u, v, w, a, b, c, indices);
+    
+function _triangulate_snipable_sub(shape_pts, n, u, v, w, a, b, c, indices, p = 0) = 
+    p == n ? true : (
+        ((p == u) || (p == v) || (p == w)) ? _triangulate_snipable_sub(shape_pts, n, u, v, w, a, b, c, indices, p + 1) : (
+            _triangulate_in_triangle(a, b, c, shape_pts[indices[p]]) ? 
+                false : _triangulate_snipable_sub(shape_pts, n, u, v, w, a, b, c, indices, p + 1)
+        )
+    );
+
+// remove the elem at idx v from indices  
+function _triangulate_remove_v(indices, v, num_of_vertices) = 
+    let(
+        nv_minuns_one = num_of_vertices - 1
+    )
+    v == 0 ? [for(i = 1; i <= nv_minuns_one; i = i + 1) indices[i]] : (
+        v == nv_minuns_one ? [for(i = 0; i < v; i = i + 1) indices[i]] : concat(
+            [for(i = 0; i < v; i = i + 1) indices[i]], 
+            [for(i = v + 1; i <= nv_minuns_one; i = i + 1) indices[i]]
+        )
+    );
+    
+function _triangulate_zero_or_value(num_of_vertices, value) = 
+    num_of_vertices <= value ? 0 : value;
+
+function _triangulate_real_triangulate_sub(shape_pts, collector, indices, v, num_of_vertices, count, epsilon) = 
+    let(
+        // idxes of three consecutive vertices
+        u = _triangulate_zero_or_value(num_of_vertices, v),     
+        vi = _triangulate_zero_or_value(num_of_vertices, u + 1), 
+        w = _triangulate_zero_or_value(num_of_vertices, vi + 1) 
+    )
+    _triangulate_snipable(shape_pts, u, vi, w, num_of_vertices, indices, epsilon) ? 
+        _triangulate_snip(shape_pts, collector, indices, u, vi, w, num_of_vertices, count, epsilon) : 
+        _triangulate_real_triangulate(shape_pts, collector, indices, vi, num_of_vertices, count, epsilon);
+        
+function _triangulate_snip(shape_pts, collector, indices, u, v, w, num_of_vertices, count, epsilon) = 
+    let(
+        a = indices[u],
+        b = indices[v],
+        c = indices[w],
+        new_nv = num_of_vertices - 1
+    )
+    _triangulate_real_triangulate( 
+        shape_pts, 
+        concat(collector, [[a, b, c]]),  
+        _triangulate_remove_v(indices, v, num_of_vertices),
+        v, 
+        new_nv,
+        2 * new_nv,
+        epsilon
+    );
+
+function _triangulate_real_triangulate(shape_pts, collector, indices, v, num_of_vertices, count, epsilon) = 
+    count <= 0 ? [] : (
+        num_of_vertices == 2 ? 
+            collector : _triangulate_real_triangulate_sub(shape_pts, collector, indices, v, num_of_vertices, count - 1,  epsilon)
+    );
+    
+function _tri_ear_clipping_impl(shape_pts,  epsilon) =
+    let(
+        num_of_vertices = len(shape_pts),
+        v = num_of_vertices - 1,
+        indices = [for(vi = 0; vi <= v; vi = vi + 1) vi],
+        count = 2 * num_of_vertices        
+    )
+    num_of_vertices < 3 ? [] : _triangulate_real_triangulate(shape_pts, [], indices, v, num_of_vertices, count, epsilon);

src/experimental/tri_ear_clipping.scad

@@ -0,0 +1,7 @@
+/**
+   copy from triangulate.scad, would move into triangle category
+**/
+
+use <experimental/_impl/_tri_ear_clipping_impl.scad>;
+    
+function tri_ear_clipping(shape_pts,  epsilon = 0.0001) = _tri_ear_clipping_impl(shape_pts,  epsilon);