Merge pull request #5158 from nortikin/curve_to_nurbs

"Curve to NURBS" node

docs/nodes/curve/curve_to_nurbs.rst

@@ -0,0 +1,142 @@
+Curve to NURBS
+==============
+
+Functionality
+-------------
+
+This node allows to:
+
+* Convert arbitrary (non-NURBS) curve to NURBS curve;
+* Reparametrize any curve: given one curve, make a NURBS curve with "natural"
+  (uniform) parametrization, or with arbitrary parametrization.
+
+More specifically, what this node does is:
+
+* Evaluates initial curve at some number of points; these node can be defined
+  by uniform distribution of curve T parameter, or by dividing curve into
+  segments of equal length. If initial curve is already NURBS or NURBS-like,
+  this node will always use curve's "fracture" (crisp) points as such base
+  points, in order to preserve fracture points at same places.
+* Interpolates a NURBS curve through these points, using one of criteria to
+  define T parameters of new curve at these points - this will define
+  parametrization of the curve.
+* In the end, resulting NURBS curve is simplified by removing as much
+  unnesessary knots as possible, while trying to change it not too much.
+
+Inputs
+------
+
+This node has the following inputs:
+
+* **Curve**. The curve to be converted to NURBS. This input is mandatory.
+* **Degree**. Degree of resulting NURBS curve. The default value is 3.
+* **Samples**. Number of base points on the curve, which will be used for
+  interpolation. More samples will give NURBS curve which follows initial curve
+  more precisely, but have more control points (and will take more time to
+  calculate). The default value is 50.
+* **LengthResolution**. This input is available only when **Parametrization**
+  parameter is set to **Natural (Curve Length)**. Resolution which is used to
+  calculate curve length. Bigger value will give more precise calculation, but
+  will take more time to calculate. The default value is 50.
+* **Parametrization**. This input is available and mandatory only when
+  **Parametrization** parameter is seto to **Arbitrary**. The curve in this
+  input defines wanted parametrization of NURBS curve. The node expects a curve
+  which lies in XOY plane and has [0; 1] as it's domain, and it's expected that
+  Y coordinate of point on the curve is growing with growth of T parameter,
+  while remaining in [0; 1] bounds.
+* **Tolerance**. This input is available only when **Simplify** parameter is
+  checked. This defines tolerance value used when removing excessive knots of
+  interpolated NURBS curve. Lower values will give curves which follow initial
+  curve more precisely, but have more control points. The default value is 1e-6
+  (one per million).
+
+Parameters
+----------
+
+This node has the following parameters:
+
+* **Parametrization**. This defines parametrization of resulting NURBS curve.
+  The available options are:
+
+  * **Natural (Curve Length)**. Curve T parameter of some point on the curve
+    will be equal (approximately) to length of the curve segment from start to
+    that point.
+  * **Keep Original**. Parametrization of resulting curve will be the same as
+    parametrization of input curve.
+  * **Arbitrary**. This allows to specify arbitrary curve parametrization by
+    providing a curve in **Parametrization** input.
+
+  The default option is **Natural (Curve Length)**.
+* **Simplify**. If checked, the node will try to simplify the curve after
+  interpolation. With big enough values of **Samples** input, interpolated
+  curve will have a lot of control points, some of which are not really
+  necessary if you do not need too much precision. Checked by default.
+
+Outputs
+-------
+
+This node has the following output:
+
+* **Curve**. The resulting NURBS curve.
+
+Examples of Usage
+-----------------
+
+General nodes setup:
+
+.. image:: ../../../docs/assets/nodes/curve/curve_to_nurbs_nodes.png
+   :target: ../../../docs/assets/nodes/curve/curve_to_nurbs_nodes.png
+
+If we specify Parametrization = "Keep Original", then for NURBS curves node
+will basically return the same curve (slightly modified due to algorithms
+involved):
+
+.. image:: ../../../docs/assets/nodes/curve/curve_to_nurbs_original.png
+   :target: ../../../docs/assets/nodes/curve/curve_to_nurbs_original.png
+
+So if you already have a NURBS curve, it does not make sense to use original
+parametrization. It may, however, make sense for generic curves, see below.
+
+In the following case we already have Bezier curve, but we want to have a NURBS
+curve with uniform parametrization:
+
+.. image:: ../../../docs/assets/nodes/curve/curve_to_nurbs_bezier_degree_3.png
+   :target: ../../../docs/assets/nodes/curve/curve_to_nurbs_bezier_degree_3.png
+
+Note that while the curve is smooth, it's curvature comb is not smooth. If we
+want it to be smooth, we can use NURBS curves of higher degree:
+
+.. image:: ../../../docs/assets/nodes/curve/curve_to_nurbs_bezier_degree_4.png
+   :target: ../../../docs/assets/nodes/curve/curve_to_nurbs_bezier_degree_4.png
+
+It is possible to create NURBS curves with arbitrary parametrization. Nodes setup:
+
+.. image:: ../../../docs/assets/nodes/curve/curve_to_nurbs_arbitrary_nodes.png
+   :target: ../../../docs/assets/nodes/curve/curve_to_nurbs_arbitrary_nodes.png
+
+"Formula interpolate" node defines the following reparametrization curve in this case:
+
+.. image:: ../../../docs/assets/nodes/curve/curve_to_nurbs_arbitrary_parametrization.png
+   :target: ../../../docs/assets/nodes/curve/curve_to_nurbs_arbitrary_parametrization.png
+
+This gives the following result:
+
+.. image:: ../../../docs/assets/nodes/curve/curve_to_nurbs_arbitrary_result.png
+   :target: ../../../docs/assets/nodes/curve/curve_to_nurbs_arbitrary_result.png
+
+Let's check with arbitrary curve; in this case it's a straight line segment
+deformed by vector noise field:
+
+.. image:: ../../../docs/assets/nodes/curve/curve_to_nurbs_noise_nodes.png
+   :target: ../../../docs/assets/nodes/curve/curve_to_nurbs_noise_nodes.png
+
+With Parametrization = "Keep Original" this gives:
+
+.. image:: ../../../docs/assets/nodes/curve/curve_to_nurbs_noise_keep.png
+   :target: ../../../docs/assets/nodes/curve/curve_to_nurbs_noise_keep.png
+
+With Parametrization = "Natural" this gives:
+
+.. image:: ../../../docs/assets/nodes/curve/curve_to_nurbs_noise_natural.png
+   :target: ../../../docs/assets/nodes/curve/curve_to_nurbs_noise_natural.png
+

index.yaml

@@ -89,6 +89,7 @@
         - SvExNurbsCurveNode
         - SvApproxNurbsCurveMk3Node
         - SvExInterpolateNurbsCurveNodeMK2
+        - SvCurveToNurbsNode
         - SvCurveDiscontinuityNode
         - SvFilletCurveNode
         - SvDeconstructCurveNode

menus/full_by_data_type.yaml

@@ -265,6 +265,7 @@
         - SvExNurbsCurveNode
         - SvApproxNurbsCurveMk3Node
         - SvExInterpolateNurbsCurveNodeMK2
+        - SvCurveToNurbsNode
         - ---
         - SvGenerateKnotvectorNode
     - Modify Curve:

menus/full_nortikin.yaml

@@ -91,6 +91,7 @@
             - SvExNurbsCurveNode
             - SvApproxNurbsCurveMk3Node
             - SvExInterpolateNurbsCurveNodeMK2
+            - SvCurveToNurbsNode
         - GC SCRIPTED:
             - icon_name: PLUGIN
             - SvExCurveFormulaNode

nodes/curve/curve_to_nurbs.py

@@ -0,0 +1,138 @@
+# This file is part of project Sverchok. It's copyrighted by the contributors
+# recorded in the version control history of the file, available from
+# its original location https://github.com/nortikin/sverchok/commit/master
+#
+# SPDX-License-Identifier: GPL3
+# License-Filename: LICENSE
+
+import numpy as np
+
+import bpy
+from bpy.props import FloatProperty, EnumProperty, BoolProperty, IntProperty
+from mathutils import Vector
+
+from sverchok.node_tree import SverchCustomTreeNode
+from sverchok.data_structure import updateNode, zip_long_repeat, repeat_last_for_length, ensure_nesting_level, get_data_nesting_level
+from sverchok.utils.curve.core import SvCurve
+from sverchok.utils.curve.nurbs_algorithms import remove_excessive_knots
+from sverchok.utils.curve.nurbs_solver_applications import curve_to_nurbs, CURVE_PARAMETER, CURVE_LENGTH, CURVE_CURVATURE, CURVE_ARBITRARY
+
+class SvCurveToNurbsNode(SverchCustomTreeNode, bpy.types.Node):
+    """
+    Triggers: Curve Rebuild NURBS
+    Tooltip: Convert arbitrary curve to NURBS
+    """
+    bl_idname = 'SvCurveToNurbsNode'
+    bl_label = 'Curve to NURBS'
+    bl_icon = 'OUTLINER_OB_EMPTY'
+    sv_icon = 'SV_CURVE_TO_NURBS'
+
+    degree :  IntProperty(
+            name = "Degree",
+            min = 1,
+            default = 3,
+            update = updateNode)
+
+    samples : IntProperty(
+            name = "Samples",
+            min = 3,
+            default = 50,
+            update = updateNode)
+
+    resolution : IntProperty(
+            name = "Length Resolution",
+            min = 10,
+            default = 50,
+            update = updateNode)
+
+    parametrizations = [
+            (CURVE_LENGTH, "Natural (Curve Length)", "Natural curve parametrization (according to curve length)", 0),
+            #(CURVE_CURVATURE, "Curvature", "Parametrization according to curvature", 1),
+            (CURVE_PARAMETER, "Keep Original", "Keep original curve parametrization", 2),
+            (CURVE_ARBITRARY, "Arbitrary", "Specify arbitrary curve parametrization", 3)
+        ]
+
+    def update_sockets(self, context):
+        self.inputs['LengthResolution'].hide_safe = self.parametrization not in {CURVE_LENGTH,CURVE_CURVATURE}
+        self.inputs['Parametrization'].hide_safe = self.parametrization != CURVE_ARBITRARY
+        self.inputs['Tolerance'].hide_safe = self.simplify != True
+        updateNode(self, context)
+
+    parametrization : EnumProperty(
+            name = "Parametrization",
+            items = parametrizations,
+            update = update_sockets)
+
+    simplify : BoolProperty(
+            name = "Simplify",
+            default = True,
+            update = update_sockets)
+
+    tolerance : FloatProperty(
+            name = "Tolerance",
+            default = 1e-6,
+            min = 0.0,
+            precision = 8,
+            update = updateNode)
+
+    def draw_buttons(self, context, layout):
+        layout.label(text='Parametrization:')
+        layout.prop(self, 'parametrization', text='')
+        layout.prop(self, 'simplify')
+
+    def sv_init(self, context):
+        self.inputs.new('SvCurveSocket', "Curve")
+        self.inputs.new('SvStringsSocket', "Degree").prop_name = 'degree'
+        self.inputs.new('SvStringsSocket', "Samples").prop_name = 'samples'
+        self.inputs.new('SvStringsSocket', "LengthResolution").prop_name = 'resolution'
+        self.inputs.new('SvCurveSocket', "Parametrization")
+        self.inputs.new('SvStringsSocket', "Tolerance").prop_name = 'tolerance'
+        self.outputs.new('SvCurveSocket', "Curve")
+        self.update_sockets(context)
+
+    def process(self):
+        if not any(socket.is_linked for socket in self.outputs):
+            return
+
+        curves_s = self.inputs['Curve'].sv_get()
+        input_level = get_data_nesting_level(curves_s, data_types=(SvCurve,))
+        curves_s = ensure_nesting_level(curves_s, 2, data_types=(SvCurve,))
+        nested_output = input_level > 1
+        degree_s = self.inputs['Degree'].sv_get()
+        degree_s = ensure_nesting_level(degree_s, 2)
+        samples_s = self.inputs['Samples'].sv_get()
+        samples_s = ensure_nesting_level(samples_s, 2)
+        resolution_s = self.inputs['LengthResolution'].sv_get()
+        resolution_s = ensure_nesting_level(resolution_s, 2)
+        tolerance_s = self.inputs['Tolerance'].sv_get()
+        tolerance_s = ensure_nesting_level(tolerance_s, 2)
+        if self.parametrization == CURVE_ARBITRARY:
+            parametrization_s = self.inputs['Parametrization'].sv_get()
+            parametrization_s = ensure_nesting_level(parametrization_s, 2, data_types=(SvCurve,))
+        else:
+            parametrization_s = [[None]]
+
+        curves_out = []
+        for params in zip_long_repeat(curves_s, degree_s, samples_s, resolution_s, tolerance_s, parametrization_s):
+            new_curves = []
+            for curve, degree, samples, resolution, tolerance, parametrization in zip_long_repeat(*params):
+                curve = curve_to_nurbs(degree, curve, samples,
+                                       method = self.parametrization,
+                                       parametrization = parametrization,
+                                       resolution = resolution,
+                                       logger = self.sv_logger)
+                if self.simplify:
+                    curve = remove_excessive_knots(curve, tolerance = tolerance)
+                new_curves.append(curve)
+            if nested_output:
+                curves_out.append(new_curves)
+            else:
+                curves_out.extend(new_curves)
+        self.outputs['Curve'].sv_set(curves_out)
+
+def register():
+    bpy.utils.register_class(SvCurveToNurbsNode)
+
+def unregister():
+    bpy.utils.unregister_class(SvCurveToNurbsNode)
+