Merge pull request #4651 from nortikin/nurbs_degree_nodes

Nurbs degree elevation & reduction nodes

docs/nodes/curve/curve_index.rst

@@ -57,6 +57,8 @@ Curves
    remove_knot
    refine_nurbs_curve
    remove_excessive_knots
+   elevate_degree
+   reduce_degree
    adaptive_plot_nurbs
    catenary_curve
    bezier_fit

docs/nodes/curve/elevate_degree.rst

@@ -0,0 +1,53 @@
+Elevate Degree (NURBS Curve)
+============================
+
+Functionality
+-------------
+
+This node elevates (increases) the degree of a NURBS curve.
+
+The opposite action can be performed with "Reduce Degree (NURBS Curve)" node.
+
+Curves of higher degrees have more control points, and so, with higher degree,
+one control point controls smaller segment of the curve.
+
+This node can work only with NURBS and NURBS-like curves.
+
+Inputs
+------
+
+This node has the following inputs:
+
+* **Curve**. The curve to perform operation on. This input is mandatory.
+* **Degree**. In **Elevate by** mode, this is the delta to be added to curve's
+  degree. In **Set degree** mode, this is new curve degree to be set. New
+  degree can not be less than current degree of the curve. The default value is
+  1.
+
+Parameters
+----------
+
+This node has the following parameter:
+
+* **Mode**. This defines how the new degree of the curve is specified:
+
+  * In **Elevate by** mode, **Degree** input specifies the number to be added
+    to current degree of the curve.
+  * In **Set degree** mode, **Degree** input specifies the new degree of the
+    curve.
+
+Outputs
+-------
+
+This node has the following output:
+
+* **Curve**. The curve of elevated degree.
+
+Example of Usage
+----------------
+
+Here orange is the original curve of 3rd degree, and green is it's control
+polygon. Red is the control polygon of curve with elevated (4th) degree.
+
+.. image:: https://user-images.githubusercontent.com/284644/189500544-0b0d70b0-f312-43b6-ac5a-b726bce6ccbd.png
+

docs/nodes/curve/reduce_degree.rst

@@ -0,0 +1,68 @@
+Reduce Degree (NURBS Curve)
+===========================
+
+Functionality
+-------------
+
+This node reduces (decreases) the degree of a NURBS curve.
+
+The action of this node is the opposite to the action of "Elevate Degree (NURBS Curve)" node.
+
+Degree reduction is the process which can not be always performed exactly. Some
+curves can not be degree reduced without visible deviation of curve's geometry.
+For other, degree reduction produces only small error.
+
+This node can work only with NURBS and NURBS-like curves.
+
+Inputs
+------
+
+This node has the following inputs:
+
+* **Curve**. The curve object to perform operation on. This input is mandatory.
+* **Degree**. In **Reduce by** mode, this is the delta to be substracted from
+  curve's degree. In **Set degree** mode, this is new curve degree to be set.
+  New degree can not be greater than current degree of the curve. The default
+  value is 1.
+* **Tolerance**. Maximum tolerable deviation of new curve from original. If
+  degree reduction process will have error estimation more than this tolerance,
+  then, depending on **Only if possible** parameter, the node will either fail or
+  return the curve untouched (or degree reduced by less than wanted value). The
+  default value is ``0.0001``.
+
+Parameters
+----------
+
+This node has the following parameters:
+
+* **Mode**. This defines how the new degree of the curve is specified:
+
+  * In **Reduce by** mode, **Degree** input specifies the number to be substracted
+    from current degree of the curve.
+  * In **Set degree** mode, **Degree** input specifies the new degree of the
+    curve.
+
+* **Only if possible**. If this flag is checked, the node will try to degree
+  reduce the curve by requested amount; it it is not possible to do so without
+  deviation greater than the specified tolerance, the node will just degree
+  reduce the curve the number of times it can. If  not checked, then the node
+  will fail (become red) in such a situation, and the processint will stop.
+  Unchecked by default.
+
+Outputs
+-------
+
+This node has the following output:
+
+* **Curve**. The resulting curve.
+
+Example of Usage
+----------------
+
+Here, the initial curve of 3rd degree is reduced to degree of 2. Orange is the
+original curve, blue is it's control polygon; green is the resulting curve, and
+red is it's control polygon. As you can see, in this case the operation could
+not be performed without visible deviation.
+
+.. image:: https://user-images.githubusercontent.com/284644/189500535-3a126895-7a36-453d-af8a-ff4b0615836e.png
+

docs/nodes/curve/remove_excessive_knots.rst

@@ -23,9 +23,8 @@ Parameters
 
 This node has the following parameter:
 
-* **Tolerance**. This parameter is available in the N panel only. This defines
-  how much is it allowed to change the shape of the curve by knot removal
-  procedure. The default value is ``10^-6``.
+* **Tolerance**. This defines how much is it allowed to change the shape of the
+  curve by knot removal procedure. The default value is ``10^-6``.
 
 Outputs
 -------

docs/nodes/surface/elevate_degree.rst

@@ -0,0 +1,61 @@
+Elevate Degree (NURBS Surface)
+==============================
+
+Functionality
+-------------
+
+This node elevates (increases) the degree of a NURBS surface.
+
+The opposite action can be performed with "Reduce Degree (NURBS Surface)" node.
+
+Surfaces of higher degrees have more control points, and so, with higher degree,
+one control point controls smaller segment of the surface.
+
+Remember that NURBS surface has two degrees, one along U parameter and one
+along V. This node can elevate any of them.
+
+This node can work only with NURBS and NURBS-like surfaces.
+
+Inputs
+------
+
+This node has the following inputs:
+
+* **Surface**. The surface to perform operation on. This input is mandatory.
+* **Degree**. In **Elevate by** mode, this is the delta to be added to surface's
+  degree. In **Set degree** mode, this is new surface degree to be set. New
+  degree can not be less than current degree of the surface. The default value is
+  1.
+
+Parameters
+----------
+
+This node has the following parameters:
+
+* **Direction**. This specifies the parameter direction, degree along which is
+  to be increased. The available options are **U** and **V**. The default
+  option is **U**.
+* **Mode**. This defines how the new degree of the surface is specified:
+
+  * In **Elevate by** mode, **Degree** input specifies the number to be added
+    to current degree of the surface.
+  * In **Set degree** mode, **Degree** input specifies the new degree of the
+    surface.
+
+Outputs
+-------
+
+This node has the following output:
+
+* **Surface**. The surface of elevated degree.
+
+Example of Usage
+----------------
+
+Here the degree of the surface is increased by 1 along U and then reduced by 1
+also along U, just to illustrate that degree elevation and reduction are the
+opposite processes. Red is the control net of the original and the resulting
+surfaces. Blue is the control polygon of degree elevated surface.
+
+.. image:: https://user-images.githubusercontent.com/284644/189500531-e4354c9d-0dd4-4bc5-861d-43d9229c28e6.png
+

docs/nodes/surface/reduce_degree.rst

@@ -0,0 +1,67 @@
+Reduce Degree (NURBS Surface)
+=============================
+
+Functionality
+-------------
+
+This node reduces (decreases) the degree of a NURBS surface.
+
+The action of this node is the opposite to the action of "Elevate Degree (NURBS Surface)" node.
+
+Degree reduction is the process which can not be always performed exactly. Some
+surfaces can not be degree reduced without visible deviation of surface's geometry.
+For other, degree reduction produces only small error.
+
+Remember that NURBS surface has two degrees, one along U parameter and one
+along V. This node can reduce any of them.
+
+This node can work only with NURBS and NURBS-like surfaces.
+
+Inputs
+------
+
+This node has the following inputs:
+
+* **Surface**. The surface to perform operation on. This input is mandatory.
+* **Degree**. In **Reduce by** mode, this is the delta to be substracted from
+  surface's degree. In **Set degree** mode, this is new surface degree to be
+  set. New degree can not be greater than current degree of the surface. The
+  default value is 1.
+* **Tolerance**. Maximum tolerable deviation of new surface from original. If
+  degree reduction process will have error estimation more than this tolerance,
+  then, depending on **Only if possible** parameter, the node will either fail or
+  return the surface untouched (or degree reduced by less than wanted value). The
+  default value is ``0.0001``.
+
+Parameters
+----------
+
+This node has the following parameters:
+
+* **Direction**. This specifies the parameter direction, degree along which is
+  to be decreased. The available options are **U** and **V**. The default
+  option is **U**.
+* **Mode**. This defines how the new degree of the surface is specified:
+
+  * In **Reduce by** mode, **Degree** input specifies the number to be
+    substracted from current degree of the surface.
+  * In **Set degree** mode, **Degree** input specifies the new degree of the
+    surface.
+
+Outputs
+-------
+
+This node has the following output:
+
+* **Surface**. The surface of a reduced degree.
+
+Example of Usage
+----------------
+
+Here the degree of the surface is increased by 1 along U and then reduced by 1
+also along U, just to illustrate that degree elevation and reduction are the
+opposite processes. Red is the control net of the original and the resulting
+surfaces. Blue is the control polygon of degree elevated surface.
+
+.. image:: https://user-images.githubusercontent.com/284644/189500531-e4354c9d-0dd4-4bc5-861d-43d9229c28e6.png
+

docs/nodes/surface/remove_excessive_knots.rst

@@ -26,9 +26,8 @@ This node has the following parameters:
 * **Direction**. This defines, in which parametric directions should the knot
   removal procedure be performed. The available options are **U+V** (both
   directions), **U** and **V**. The default value is **U+V**.
-* **Tolerance**. This parameter is available in the N panel only. This defines
-  how much is it allowed to change the shape of the surface by knot removal
-  procedure. The default value is ``10^-6``.
+* **Tolerance**. This defines how much is it allowed to change the shape of the
+  surface by knot removal procedure. The default value is ``10^-6``.
 
 Outputs
 -------

docs/nodes/surface/surface_index.rst

@@ -42,6 +42,8 @@ Surface
    insert_knot
    remove_knot
    remove_excessive_knots
+   elevate_degree
+   reduce_degree
    intersect_curve_surface
    nearest_point
    ortho_project

index.md

@@ -77,6 +77,9 @@
     SvRefineNurbsCurveNode
     SvCurveRemoveExcessiveKnotsNode
     ---
+    SvCurveElevateDegreeNode
+    SvCurveReduceDegreeNode
+    ---
     SvAdaptivePlotNurbsCurveNode
 
 ## Curves @ Bezier
@@ -151,6 +154,9 @@
     SvSurfaceInsertKnotNode
     SvSurfaceRemoveKnotNode
     SvSurfaceRemoveExcessiveKnotsNode
+    ---
+    SvSurfaceElevateDegreeNode
+    SvSurfaceReduceDegreeNode
 
 ## Surfaces
     SvExPlaneSurfaceNode