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+from PandaModules import *
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+import types
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+
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+class Rope(NodePath):
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+ """
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+ This class defines a Nurbs curve whose control vertices are
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+ defined based on points relative to one or more nodes in space, so
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+ that the "rope" will animate as the nodes move around. It uses
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+ the C++ RopeNode class to achieve fancy rendering effects like
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+ thick lines built from triangle strips.
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+ """
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+
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+ showRope = base.config.GetBool('show-rope', 1)
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+
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+ def __init__(self, name = 'Rope'):
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+ self.ropeNode = RopeNode(name)
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+ self.curve = NurbsCurveEvaluator()
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+ self.ropeNode.setCurve(self.curve)
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+ NodePath.__init__(self, self.ropeNode)
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+ self.name = name
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+
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+ def setup(self, order, verts, knots = None):
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+ # This must be called to define the shape of the curve
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+ # initially, and may be called again as needed to adjust the
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+ # curve's properties.
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+
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+ # order must be either 1, 2, 3, or 4, and is one more than the
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+ # degree of the curve; most NURBS curves are order 4.
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+
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+ # verts is a list of (NodePath, point) tuples, defining the
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+ # control vertices of the curve. For each control vertex, the
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+ # NodePath may refer to an arbitrary node in the scene graph,
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+ # indicating the point should be interpreted in the coordinate
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+ # space of that node (and it will automatically move when the
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+ # node is moved), or it may be the empty NodePath or None to
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+ # indicate the point should be interpreted in the coordinate
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+ # space of the Rope itself. Each point value may be either a
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+ # 3-tuple or a 4-tuple (or a VBase3 or VBase4). If it is a
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+ # 3-component vector, it represents a 3-d point in space; a
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+ # 4-component vector represents a point in 4-d homogeneous
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+ # space; that is to say, a 3-d point and an additional weight
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+ # factor (which should have been multiplied into the x y z
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+ # components).
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+
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+ # knots is optional. If specified, it should be a list of
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+ # floats, and should be of length len(verts) + order. If it
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+ # is omitted, a default knot string is generated that consists
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+ # of the first (order - 1) and last (order - 1) values the
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+ # same, and the intermediate values incrementing by 1.
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+
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+ self.order = order
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+ self.verts = verts
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+ self.knots = knots
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+
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+ self.recompute()
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+
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+ def recompute(self):
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+ # Recomputes the curve after its properties have changed.
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+ # Normally it is not necessary for the user to call this
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+ # directly.
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+
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+ if not self.showRope:
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+ return
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+ numVerts = len(self.verts)
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+ self.curve.reset(numVerts)
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+ self.curve.setOrder(self.order)
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+ for i in range(numVerts):
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+ nodePath, point = self.verts[i]
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+ if isinstance(point, types.TupleType):
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+ if (len(point) >= 4):
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+ self.curve.setVertex(i, VBase4(point[0], point[1], point[2], point[3]))
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+ else:
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+ self.curve.setVertex(i, VBase3(point[0], point[1], point[2]))
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+ else:
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+ self.curve.setVertex(i, point)
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+ if nodePath:
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+ self.curve.setVertexSpace(i, nodePath)
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+
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+ if self.knots != None:
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+ for i in range(len(self.knots)):
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+ self.curve.setKnot(i, self.knots[i])
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+
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+ self.ropeNode.resetBound(self)
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+
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+ def getPoints(self, len):
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+ # Returns a list of len points, evenly distributed in
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+ # parametric space on the rope, in the coordinate space of the
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+ # Rope itself.
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+
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+ result = self.curve.evaluate(self)
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+ numPts = len
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+ ropePts = []
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+ for i in range(numPts):
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+ pt = Point3()
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+ result.evalPoint(i / float(numPts - 1), pt)
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+ ropePts.append(pt)
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+ return ropePts
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David Rose