Source code for direct.showutil.Rope

```from panda3d.core import *

[docs]class Rope(NodePath):
"""
This class defines a NURBS curve whose control vertices are
defined based on points relative to one or more nodes in space, so
that the "rope" will animate as the nodes move around.  It uses
the C++ RopeNode class to achieve fancy rendering effects like
thick lines built from triangle strips.
"""

showRope = ConfigVariableBool('show-rope', True, \
"Set this to false to deactivate the display of ropes.")

[docs]    def __init__(self, name = 'Rope'):
self.ropeNode = RopeNode(name)
self.curve = NurbsCurveEvaluator()
self.ropeNode.setCurve(self.curve)
NodePath.__init__(self, self.ropeNode)
self.name = name
self.order = 0
self.verts = []
self.knots = None

[docs]    def setup(self, order, verts, knots = None):
"""This must be called to define the shape of the curve
initially, and may be called again as needed to adjust the
curve's properties.

order must be either 1, 2, 3, or 4, and is one more than the
degree of the curve; most NURBS curves are order 4.

verts is a list of (NodePath, point) tuples, defining the
control vertices of the curve.  For each control vertex, the
NodePath may refer to an arbitrary node in the scene graph,
indicating the point should be interpreted in the coordinate
space of that node (and it will automatically move when the
node is moved), or it may be the empty NodePath or None to
indicate the point should be interpreted in the coordinate
space of the Rope itself.  Each point value may be either a
3-tuple or a 4-tuple (or a VBase3 or VBase4).  If it is a
3-component vector, it represents a 3-d point in space; a
4-component vector represents a point in 4-d homogeneous
space; that is to say, a 3-d point and an additional weight
factor (which should have been multiplied into the x y z
components).

verts may be a list of dictionaries instead of a list of
tuples.  In this case, each vertex dictionary may have any of
the following elements:

'node' : the NodePath indicating the coordinate space
'point' : the 3-D point relative to the node; default (0, 0, 0)
'color' : the color of the vertex, default (1, 1, 1, 1)
'thickness' : the thickness at the vertex, default 1

In order to enable the per-vertex color or thickness, you must
call rope.ropeNode.setUseVertexColor(1) or
rope.ropeNode.setUseVertexThickness(1).

knots is optional.  If specified, it should be a list of
floats, and should be of length len(verts) + order.  If it
is omitted, a default knot string is generated that consists
of the first (order - 1) and last (order - 1) values the
same, and the intermediate values incrementing by 1.
"""

self.order = order
self.verts = verts
self.knots = knots

self.recompute()

[docs]    def recompute(self):
"""Recomputes the curve after its properties have changed.
Normally it is not necessary for the user to call this
directly."""

if not self.showRope:
return
numVerts = len(self.verts)
self.curve.reset(numVerts)
self.curve.setOrder(self.order)

defaultNodePath = None
defaultPoint = (0, 0, 0)
defaultColor = (1, 1, 1, 1)
defaultThickness = 1

useVertexColor = self.ropeNode.getUseVertexColor()
useVertexThickness = self.ropeNode.getUseVertexThickness()

vcd = self.ropeNode.getVertexColorDimension()
vtd = self.ropeNode.getVertexThicknessDimension()

for i in range(numVerts):
v = self.verts[i]
if isinstance(v, tuple):
nodePath, point = v
color = defaultColor
thickness = defaultThickness
else:
nodePath = v.get('node', defaultNodePath)
point = v.get('point', defaultPoint)
color = v.get('color', defaultColor)
thickness = v.get('thickness', defaultThickness)

if isinstance(point, tuple):
if (len(point) >= 4):
self.curve.setVertex(i, VBase4(point[0], point[1], point[2], point[3]))
else:
self.curve.setVertex(i, VBase3(point[0], point[1], point[2]))
else:
self.curve.setVertex(i, point)
if nodePath:
self.curve.setVertexSpace(i, nodePath)
if useVertexColor:
self.curve.setExtendedVertex(i, vcd + 0, color[0])
self.curve.setExtendedVertex(i, vcd + 1, color[1])
self.curve.setExtendedVertex(i, vcd + 2, color[2])
self.curve.setExtendedVertex(i, vcd + 3, color[3])
if useVertexThickness:
self.curve.setExtendedVertex(i, vtd, thickness)

if self.knots != None:
for i in range(len(self.knots)):
self.curve.setKnot(i, self.knots[i])

self.ropeNode.resetBound(self)

[docs]    def getPoints(self, len):
"""Returns a list of len points, evenly distributed in
parametric space on the rope, in the coordinate space of the
Rope itself."""

result = self.curve.evaluate(self)
startT = result.getStartT()
sizeT = result.getEndT() - startT

numPts = len
ropePts = []
for i in range(numPts):
pt = Point3()
result.evalPoint(sizeT * i / float(numPts - 1) + startT, pt)
ropePts.append(pt)
return ropePts
```