Generalize Coons Patch node.

docs/nodes/surface/coons_patch.rst

@@ -1,5 +1,5 @@
-Surface from Four Curves
-========================
+Surface from Boundary Curves
+============================
 
 Functionality
 -------------
@@ -18,6 +18,11 @@ That is, the second curve must begin at the point where the first curve ends;
 and the third curve must begin at the point where the second curve ends; and so
 on.
 
+It is also possible to omit the fourth curve, thus to build a surface from
+three boundary curves. If the third curve does not end in the same point where
+the first curve started, the node will use a straight line segment as fourth
+curve.
+
 The surface is calculated as a Coons patch, see https://en.wikipedia.org/wiki/Coons_patch.
 
 When all provided curves are NURBS or NURBS-like, then the node will try to
@@ -34,12 +39,13 @@ This node has the following inputs:
 
 * **Curves**. The list of curves to build a surface form. This input can accept
   data with nesting level of 1 or 2 (list of curves or list of lists of
-  curves). Each list of curves must have length of 4. This input is available
+  curves). Each list of curves must have length of 3 or 4. This input is available
   and mandatory only if **Input** parameter is set to **List of Curves**.
 * **Curve1**, **Curve2**, **Curve3**, **Curve4**. Curves to build surface from.
   These inputs can accept data with nesting level 1 only (list of curves).
-  These inputs are available and mandatory only if **Input** parameter is set
-  to **4 Curves**.
+  These inputs are available only if **Input** parameter is set
+  to **4 Curves**. Inputs **Curve1**, **Curve2** and **Curve3** are mandatory.
+  **Curve4** input is optional.
 
 Parameters
 ----------
@@ -49,7 +55,7 @@ This node has the following parameters:
 * **Input**. This defines how the curves are provided. The following options are available:
 
   * **List of curves**. All curves are provided in a single input **Curves**.
-  * **4 Curves**. Each curve is provided in separate input **Curve1** - **Curve4**.
+  * **Separate inputs**. Each curve is provided in separate input **Curve1** - **Curve4**.
 
   The default value is **List of Curves**.
 
@@ -103,3 +109,12 @@ It is possible to use the node together with "Split Curve" node to generate a su
 
 .. image:: https://user-images.githubusercontent.com/284644/82479760-3deb1f80-9aec-11ea-8411-22ffd273259f.png
 
+It is possible to use only three boundary curves:
+
+.. image:: https://user-images.githubusercontent.com/284644/210209607-113759b7-9992-4e5d-870d-6aa6dafe0c32.png
+
+If the third curve end does not coincide with the beginning of the first curve,
+the node will close the cycle with a straight line segment:
+
+.. image:: https://user-images.githubusercontent.com/284644/210209611-052c63b6-ef39-4c12-a047-d7d369f3469c.png
+

nodes/surface/coons_patch.py

@@ -6,16 +6,17 @@
 
 from sverchok.node_tree import SverchCustomTreeNode
 from sverchok.data_structure import updateNode, zip_long_repeat, ensure_nesting_level
-from sverchok.utils.curve import SvCurve
+from sverchok.utils.curve.core import SvCurve
+from sverchok.utils.curve.primitives import SvLine, SvPointCurve
 from sverchok.utils.surface.coons import coons_surface, GENERIC, NURBS_ONLY, NURBS_IF_POSSIBLE
 
 class SvCoonsPatchNode(SverchCustomTreeNode, bpy.types.Node):
     """
-    Triggers: Coons Patch / Surface form four curves
-    Tooltip: Generate a surface (Coons Patch) from four boundary curves
+    Triggers: Coons Patch / Surface form three or four boundary curves
+    Tooltip: Generate a surface (Coons Patch) from three or four boundary curves
     """
     bl_idname = 'SvCoonsPatchNode'
-    bl_label = 'Surface from Four Curves'
+    bl_label = 'Surface from Boundary Curves'
     bl_icon = 'SURFACE_DATA'
     sv_icon = 'SV_COONS_PATCH'
 
@@ -53,8 +54,8 @@ def update_sockets(self, context):
         updateNode(self, context)
 
     modes = [
-            ('LIST', "List of curves", "Input is provided as a list of curves, which must have 4 items", 0),
-            ('FOUR', "4 curves", "Four separate Curve inputs are provided", 1)
+            ('LIST', "List of curves", "Input is provided as a list of curves, which must have 3 or 4 items", 0),
+            ('FOUR', "Separate inputs", "Three or four separate Curve inputs are provided", 1)
         ]
 
     input_mode : EnumProperty(
@@ -83,6 +84,8 @@ def run_check(self, curves):
         pairs = list(zip(curves, curves[1:]))
         pairs.append((curves[-1], curves[0]))
         for idx, (curve1, curve2) in enumerate(pairs):
+            if curve1 is None or curve2 is None:
+                    continue
             _, t_max_1 = curve1.get_u_bounds()
             t_min_2, _ = curve2.get_u_bounds()
             end1 = curve1.evaluate(t_max_1)
@@ -91,24 +94,39 @@ def run_check(self, curves):
             if distance > self.max_rho:
                 raise Exception("Distance between the end of {}'th curve and the start of {}'th curve is {} - too much".format(idx, idx+1, distance))
 
+    def make_closing_curve(self, first_curve, last_curve):
+        pt1 = last_curve.get_end_points()[1]
+        pt2 = first_curve.get_end_points()[0]
+        if np.linalg.norm(pt1 - pt2) < 1e-6:
+            return SvPointCurve(pt1)
+        else:
+            return SvLine.from_two_points(pt1, pt2)
+
     def get_input(self):
         if self.input_mode == 'LIST':
             curve_list_s = self.inputs['Curves'].sv_get()
             curve_list_s = ensure_nesting_level(curve_list_s, 2, data_types=(SvCurve,))
             for curves in curve_list_s:
+                if len(curves) == 3:
+                    curve4 = None
+                    curves.append(curve4)
                 if len(curves) != 4:
                     raise Exception("List of curves must contain exactly 4 curve objects!")
                 yield curves
         else:
             curve1_s = self.inputs['Curve1'].sv_get()
             curve2_s = self.inputs['Curve2'].sv_get()
             curve3_s = self.inputs['Curve3'].sv_get()
-            curve4_s = self.inputs['Curve4'].sv_get()
 
             curve1_s = ensure_nesting_level(curve1_s, 1, data_types=(SvCurve,))
             curve2_s = ensure_nesting_level(curve2_s, 1, data_types=(SvCurve,))
             curve3_s = ensure_nesting_level(curve3_s, 1, data_types=(SvCurve,))
-            curve4_s = ensure_nesting_level(curve4_s, 1, data_types=(SvCurve,))
+
+            if self.inputs['Curve4'].is_linked:
+                curve4_s = self.inputs['Curve4'].sv_get()
+                curve4_s = ensure_nesting_level(curve4_s, 1, data_types=(SvCurve,))
+            else:
+                curve4_s = [None]
 
             for curve1, curve2, curve3, curve4 in zip_long_repeat(curve1_s, curve2_s, curve3_s, curve4_s):
                 yield [curve1, curve2, curve3, curve4]
@@ -121,6 +139,8 @@ def process(self):
         for curves in self.get_input():
             if self.check:
                 self.run_check(curves)
+            if curves[3] is None:
+                curves[3] = self.make_closing_curve(curves[0], curves[2])
             surface = coons_surface(*curves, use_nurbs=self.use_nurbs)
             surface_out.append(surface)
 

utils/curve/bezier.py

@@ -75,7 +75,7 @@ class SvBezierCurve(SvCurve, SvBezierSplitMixin):
     Bezier curve of arbitrary degree.
     """
     def __init__(self, points):
-        self.points = points
+        self.points = np.asarray(points)
         self.tangent_delta = 0.001
         n = self.degree = len(points) - 1
         self.__description__ = "Bezier[{}]".format(n)

utils/curve/primitives.py

@@ -145,6 +145,63 @@ def get_polyline_vertices(self):
     def is_closed(self, *args):
         return False
 
+    def extrude_along_vector(self, vector):
+        return self.to_nurbs().extrude_along_vector(vector)
+
+    def make_revolution_surface(self, point, direction, v_min, v_max, global_origin):
+        return self.to_nurbs().make_revolution_surface(point, direction, v_min, v_max, global_origin)
+
+    def make_ruled_surface(self, curve2, vmin, vmax):
+        return self.to_nurbs().make_ruled_surface(curve2, vmin, vmax)
+
+    def extrude_to_point(self, point):
+        return self.to_nurbs().extrude_to_point(point)
+
+    def lerp_to(self, curve2, coefficient):
+        return self.to_nurbs().lerp_to(curve2, coefficient)
+
+class SvPointCurve(SvCurve):
+    __description__ = "Single-Point"
+
+    def __init__(self, point):
+        self.point = np.asarray(point)
+
+    def evaluate(self, t):
+        return self.point
+
+    def evaluate_array(self, ts):
+        points = np.empty((len(ts),3))
+        points[:] = self.point
+        return points
+
+    def get_u_bounds(self):
+        return (0.0, 1.0)
+
+    def get_degree(self):
+        return 1
+
+    def to_bezier(self):
+        u_min, u_max = self.get_u_bounds()
+        p1 = self.evaluate(u_min)
+        p2 = self.evaluate(u_max)
+        return SvBezierCurve([p1, p2])
+
+    def to_bezier_segments(self):
+        return [self.to_bezier()]
+
+    def is_closed(self, *args):
+        return False
+
+    def concatenate(self, curve2, *args):
+        return curve2
+
+    def to_nurbs(self, implementation = SvNurbsMaths.NATIVE):
+        return self.to_bezier().to_nurbs()
+
+    def reverse(self):
+        return SvPointCurve(self.point)
+
+
 def rotate_radius(radius, normal, thetas):
     """Internal method"""
     ct = np.cos(thetas)[np.newaxis].T

utils/surface/coons.py

@@ -12,7 +12,7 @@
 from sverchok.utils.curve import knotvector as sv_knotvector
 from sverchok.utils.curve.core import UnsupportedCurveTypeException
 from sverchok.utils.curve.nurbs import SvNurbsCurve
-from sverchok.utils.curve.algorithms import reverse_curve, reparametrize_curve
+from sverchok.utils.curve.algorithms import reverse_curve, reparametrize_curve, unify_curves_degree
 from sverchok.utils.curve.nurbs_algorithms import unify_curves, unify_two_curves
 from sverchok.utils.surface.core import SvSurface
 from sverchok.utils.surface.nurbs import SvNurbsSurface
@@ -83,10 +83,11 @@ def coons_surface(curve1, curve2, curve3, curve4, use_nurbs=NURBS_IF_POSSIBLE):
             return SvCoonsSurface(*curves)
     try:
         nurbs_curves = [c.reparametrize(0,1) for c in nurbs_curves]
-        degrees = [c.get_degree() for c in nurbs_curves]
         implementation = nurbs_curves[0].get_nurbs_implementation()
 
+        nurbs_curves[0], nurbs_curves[2] = unify_curves_degree([nurbs_curves[0], nurbs_curves[2]])
         nurbs_curves[0], nurbs_curves[2] = unify_curves([nurbs_curves[0], nurbs_curves[2]])
+        nurbs_curves[1], nurbs_curves[3] = unify_curves_degree([nurbs_curves[1], nurbs_curves[3]])
         nurbs_curves[1], nurbs_curves[3] = unify_curves([nurbs_curves[1], nurbs_curves[3]])
 
         degree_u = nurbs_curves[0].get_degree()