"Bevel a Curve (Surface)" node et al

docs/nodes/modifier_make/bevel_curve.rst

@@ -1,5 +1,5 @@
-Bevel a Curve
-=============
+Bevel a Curve (Mesh)
+====================
 
 Functionality
 -------------

docs/nodes/surface/bevel_curve.rst

@@ -0,0 +1,175 @@
+Bevel a Curve (Surface)
+=======================
+
+Functionality
+-------------
+
+This node provides functionality similar to Blender's standard "bevel curve"
+feature_. More precisely, it extrudes one flat curve (called "profile curve")
+along another curve (path). Scale of "profile curve" may vary along the curve,
+as it is controlled by third curve (called "taper curve").
+
+.. _feature: https://docs.blender.org/manual/en/latest/modeling/curves/properties/geometry.html
+
+It is in general not a trivial task to rotate a 3D object along a vector,
+because there are always 2 other axes of object and it is not clear where
+should they be directed to. So, this node supports 3 different algorithms of
+object rotation calculation. In many simple cases, all these algorithms will
+give exactly the same result. But in more complex setups, or in some corner
+cases, results can be very different. So, just try all algorithms and see which
+one fits you better.
+
+* "Frenet" or "Zero-Twist" algorithms give very good results in case when
+  extrusion curve has non-zero curvature in all points. If the extrusion curve
+  has zero curvature points, or, even worse, it has straight segments, these
+  algorithms will either make "flipping" surface, or give an error.
+* "Householder", "Tracking" and "Rotation difference" algorithms are
+  "curve-agnostic", they work independently of curve by itself, depending only
+  on tangent direction. They give "good enough" result (at least, without
+  errors or sudden flips) for all extrusion curves, but may make twisted
+  surfaces in some special cases.
+* "Track normal" algorithm is supposed to give good results without twisting
+  for all extrusion curves. It will give better results with higher values of
+  "resolution" parameter, but that may be slow.
+
+**Note 1**: Taper is supposed to be an open Curve, elongated along one of
+coordinate axes (X, Y or Z). That must be the orientation axis, i.e. the axis
+perpendicular to the plane of bevel object.
+
+In the most common case, "profile curve" will lay in XY plane, so that
+orientation axis will be Z.
+
+This node can function in several modes:
+
+* Generic surface. In this mode, the node can process arbitrary Curve objects,
+  and will generate a generic Surface object.
+* NURBS surface by simple algorithm. In this mode, the node can process only
+  NURBS or NURBS-like curves, and will generate a NURBS surface. This algorithm
+  generates a minimal amount of control points; so, the generated surface may
+  follow the path curve only approximately. On the other hand, this is the
+  fastest of NURBS modes of this node.
+* NURBS surface with refinement. In this mode, the node can process only
+  NURBS or NURBS-like curves, and will generate a NURBS surface. This algorithm
+  first refines taper curve (i.e., adds some number of additional knots in it),
+  and then applies the "simple" algorithm. This algorithm produces more control
+  points, and that allows it to generate a surface which follows the path and
+  taper curves more precisely.
+* NURBS Gordon surface:
+
+   * Refine taper curve;
+   * Generate a number of copies of taper curve, bent along the path curve, and
+     rotated around it, according to the profile curve.
+   * Generate a number of copies of profile curve, rotated and placed along the
+     path curve, scaled according to the taper curve.
+   * Use these two series of curves to generate a surface by use of Gordon
+     algorithm.
+
+   For smooth curves, Gordon algorithm is supposed to be the most precise of
+   NURBS modes of this node; but it is also the slowest one.
+
+   **Note 2**: Gordon algorithm does not support use of rational curves as either
+   profile or taper.
+
+   **Note 3**: Gordon algorithm can not produce surfaces with hard edges. If
+   you provide it with profile curve which has hard turns (discontinuities of
+   curve's derivative), the output will look weird.
+
+With last two modes, this node can generate a surface with large number of
+control points. It can be wise to use "Remove excessive knots" node to simplify
+the surface.
+
+Inputs
+------
+
+This node has the following inputs:
+
+* **Path**. Path curve. This input is mandatory.
+* **Profile**. Profile curve. This input is mandatory.
+* **Taper**. Taper curve. If this input is not connected, constant taper will
+  be used.
+* **Resolution**. Path length calculation resolution. This input is available
+  only when **Samples distribution** parameter is set to **Curve length**. The
+  default value is 50.
+* **ProfileCopies**. This input is available only when **Mode** parameter is
+  set to **NURBS**, and **Precision** parameter is set to **Gordon**. Number of
+  copies of profile curve to be generated and distributed along the path curve,
+  in order to build a Gordon surface. The default value is 10.
+* **TaperRefine**. This input is available only when **Mode** parameter is
+  set to **NURBS**, and **Precision** parameter is set to **Refine** or
+  **Gordon**. Number of additional knots to be inserted in the taper curve. The
+  default value is 20.
+* **TaperCopies**. This input is available only when **Mode** parameter is
+  set to **NURBS**, and **Precision** parameter is set to **Gordon**. Number of
+  copies of the taper curve to be rotated and bent along the path curve, in
+  order to build a Gordon surface. The default value is 10.
+
+Parameters
+----------
+
+This node has the following parameters:
+
+* **Mode**. The following modes are available:
+
+  * **Generic**. The node will process arbitrary curves and output a generic
+    Surface object.
+  * **NURBS**. The node will process NURBS or NURBS-like curves and output a
+    NURBS surface.
+
+  The default mode is **Generic**.
+
+* **Precision**. This parameter is only available when **Mode** algorithm is
+  set to **NURBS**. Defines the algorithm to be used to generate control points
+  of the NURBS surface. The available options are: **Simple**, **Refine** and
+  **Gordon**. See Functionality section for description of these algorithms.
+* **Orientation**. The axis of "bevel object", which should be oriented along
+  the path. Default value is Z (which means that bevel object should lay in XY plane).
+* **Algorithm**. Rotation calculation algorithm. Available values are:
+
+  * Householder: calculate rotation by using Householder's reflection matrix
+    (see Wikipedia_ article).                   
+  * Tracking: use the same algorithm as in Blender's "TrackTo" kinematic
+    constraint. This algorithm gives you a bit more flexibility comparing to
+    other, by allowing to select the Up axis.                                                         
+  * Rotation difference: calculate rotation as rotation difference between two
+    vectors.                                         
+  * Frenet: rotate the space according to curve's Frenet frame.
+  * Zero-Twist: rotate the space according to curve's "zero-twist" frame.
+  * Track normal: try to maintain constant normal direction by tracking it along the curve.
+
+  Default value is Householder.
+
+* **Up axis**.  Axis of donor object that should point up in result. This
+  parameter is available only when Tracking algorithm is selected.  Value of
+  this parameter must differ from **Orientation** parameter, otherwise you will
+  get an error. Default value is X.
+* **Samples distribution**. This defines how the scaling of the space along the path
+  curve is to be calculated. The available options are:
+
+   * **Curve parameter**. Scale the space proportional to curve's T parameter.
+   * **Curve length**. Scale the space proportional to curve's length. This
+     usually gives more natural results, but takes more time to compute.
+
+  The default option is **Curve parameter**.
+
+.. _Wikipedia: https://en.wikipedia.org/wiki/QR_decomposition#Using_Householder_reflections
+
+Outputs
+-------
+
+This node has the following output:
+
+* **Surface**. The generated Surface object.
+
+Examples of Usage
+-----------------
+
+Example 1:
+
+.. image:: https://user-images.githubusercontent.com/284644/128608455-8bcf578f-6de4-4f28-a7aa-c5c0737d998e.png
+
+Example 2:
+
+.. image:: https://user-images.githubusercontent.com/284644/128609193-25240b31-1e4f-49d3-81f0-0df70863ccec.png
+
+.. image:: https://user-images.githubusercontent.com/284644/128609192-06d65d48-7875-4dce-a084-c4e4c700be04.png
+

docs/nodes/surface/surface_index.rst

@@ -13,6 +13,7 @@ Surface
    interpolating_surface
    revolution_surface
    taper_sweep
+   bevel_curve
    extrude_vector
    extrude_point
    extrude_curve

docs/nodes/surface/taper_sweep.rst

@@ -26,6 +26,21 @@ This node has the following inputs:
 * **Point**. The point on the taper axis line. The default value is `(0, 0, 0)`.
 * **Direction**. The directing vector of the taper axis line. The default value is `(0, 0, 1)` (Z axis).
 
+Parameters
+----------
+
+This node has the following parameters:
+
+* **NURBS**. If enabled, the node will expect NURBS (or NURBS-like) curves as
+  input, and output a NURBS surface. Otherwise, the node can process arbitrary
+  curves, and will output a generic Surface object. Unchecked by default.
+* **Scale**. This defines the scale of resulting surface in the plane
+  perpendicular to taper axis. The available options are:
+
+   * **Unit**.
+   * **Profile**. The surface will be scaled in order to match the profile curve.
+   * **Taper**. The surface will be scaled in order to match the taper curve.
+
 Outputs
 -------
 
@@ -40,3 +55,7 @@ The taper curve is generated by "filleting" some line; the profile curve is fill
 
 .. image:: https://user-images.githubusercontent.com/284644/79348542-8ee88080-7f4e-11ea-972b-50b9d6909734.png
 
+Example of NURBS mode:
+
+.. image:: https://user-images.githubusercontent.com/284644/128603194-ae5b6c3f-a4f8-43ae-89f9-00bb0ac05953.png
+

index.md

@@ -157,6 +157,7 @@
     ---
     SvExRevolutionSurfaceNode
     SvExTaperSweepSurfaceNode
+    SvBendCurveSurfaceNode
     SvExExtrudeCurveVectorNode
     SvExExtrudeCurveCurveSurfaceNode
     SvExExtrudeCurvePointNode

nodes/modifier_make/bevel_curve.py

@@ -25,11 +25,11 @@
 class SvBevelCurveNode(bpy.types.Node, SverchCustomTreeNode):
     """
     Triggers: Bevel Curve
-    Tooltip: Bevel a Curve (a.k.a. Extrude along Path)
+    Tooltip: Bevel a Curve (a.k.a. Extrude along Path) - mesh
     """
 
     bl_idname = 'SvBevelCurveNode'
-    bl_label = 'Bevel a Curve'
+    bl_label = 'Bevel a Curve (Mesh)'
     bl_icon = 'MOD_CURVE'
 
     algorithms = [