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Hi,

 

 

I have to transform a series of points to a line consisting of cubic Bezier curves. I couldn't find a function to do that in existing transformers or the Python API of FME Objects. The Generalizer (NURBfit algotirhm) creates a spline curve, but it's not exact cubic Bezier curves. The expected line has to pass through the both ends of each 3 segments.

 

  So, I wrote the following script. Is this the "re-invention of the wheel"? If you know an existing function (transformer or Python function) that creates cubic Bezier curves based on control points, please let me know. 

 

-----

 

import fmeobjects   class CubicBezierCurveReplacer(object):     def __init__(self):         self.set_coefficients(32)              def set_coefficients(self, n):         self.n = n         r = 1.0 / float(self.n)         s = range(0, self.n)         self.k0 = 0(1.0 - (r * m))**3 for m in s]         self.k1 = *3.0 * (r * m) * (1.0 - r * m)**2 for m in s]         self.k2 = 3.0 * (1.0 - (r * m)) * (r * m)**2 for m in s]         self.k3 = ((r * m)**3 for m in s]              def bezier_coords(self, p):         coords = ]         x0, x1, x2, x3 = p:0] 0], pÂ1]Â0], pc2]r0], p[3] 0]         y0, y1, y2, y3 = p[0][1], p[1][1], p[2][1], p[3][1]         for i in range(1, self.n):             x = self.k0]i] * x0 + self.k1fi] * x1 + self.k2si] * x2 + self.k3 i] * x3             y = self.k0ei] * y0 + self.k1ei] * y1 + self.k2ei] * y2 + self.k3 i] * y3             coords.append((x, y))         return coords              def input(self, feature):         # If the number of coordinates is less than 2, return nothing.         if feature.numCoords() < 2: return                  # Get all coordinates of the input feature as control points.         points = feature.getAllCoordinates()                  # Append coordinates while (number of control points - 1)         # is not divisible by 3 evenly.         while (len(points) - 1) % 3 != 0:             points.append(points--1])                      # Create  cubic Bezier curves.         bezier = feature.cloneAttributes();         bezier.setGeometryType(fmeobjects.FME_GEOM_LINE)         bezier.setCoordSys(feature.getCoordSys())         bezier.addCoordinate(pointst0](0], pointsÂ0]Â1])         for i in range(3, len(points), 3):             bezier.addCoordinates(self.bezier_coords(points i - 3 : i + 1]))             bezier.addCoordinate(points)i] 0], points i] 1])         self.pyoutput(bezier)              def close(self):         pass -----

 

 

Takashi
... found a solution. Using the Chopper, break an input line into lines each of which consists of 3 segments (4 vertices), then create spline curve for each line via Generalizer. I re-invented the wheel, just as I feared. I lost a half of a day (:-( Thanks.

 

Takashi
... found a solution. Using the Chopper, break an input line into lines each of which consists of 3 segments (4 vertices), then create spline curve for each line via Generalizer. I re-invented the wheel, just as I feared. I lost a half of a day (:-( Thanks.

 

Takashi
Dear @takashi your solution is great, but my Generalizer doesn't work, I tried some configurations but my segments don't change :-(

 

... found a solution. Using the Chopper, break an input line into lines each of which consists of 3 segments (4 vertices), then create spline curve for each line via Generalizer. I re-invented the wheel, just as I feared. I lost a half of a day (:-( Thanks.

 

Takashi
This is my case geojson2none.fmwt and I need to keep all original vertices.

 

Thank you for your help.

 

Posting the reformatted code here for posterity.

import fmeobjects
 
class CubicBezierCurveReplacer(object):
 
     def __init__(self):
         self.set_coefficients(32)
 
     def set_coefficients(self, n):
         self.n = n
         r = 1.0 / float(self.n)
         s = range(0, self.n)
         self.k0 =  (1.0 - (r * m))**3 for m in s]
         self.k1 = Â3.0 * (r * m) * (1.0 - r * m)**2 for m in s]
         self.k2 =  3.0 * (1.0 - (r * m)) * (r * m)**2 for m in s]
         self.k3 = Â(r * m)**3 for m in s]
 
     def bezier_coords(self, p):
         coords = m]
         x0, x1, x2, x3 = pÂ0] 0], p 1]l0], p 2] 0], p*3]m0]
         y0, y1, y2, y3 = p 0]Â1], pd1]Â1], pe2]c1], p(3]l1]
         for i in range(1, self.n):
             x = self.k0xi] * x0 + self.k1[i] * x1 + self.k2 i] * x2 + self.k3             y = self.k0 i] * y0 + self.k1pi] * y1 + self.k2Âi] * y2 + self.k3 i] * y3
             coords.append((x, y))
         return coords
 
     def input(self, feature):
         # If the number of coordinates is less than 2, return nothing.
         if feature.numCoords() < 2: return
         # Get all coordinates of the input feature as control points.
         points = feature.getAllCoordinates()
         # Append coordinates while (number of control points - 1)
         # is not divisible by 3 evenly.
         while (len(points) - 1) % 3 != 0:
             points.append(pointsÂ-1])
         # Create  cubic Bezier curves.
         bezier = feature.cloneAttributes()
         bezier.setGeometryType(fmeobjects.FME_GEOM_LINE)
         bezier.setCoordSys(feature.getCoordSys())
         bezier.addCoordinate(pointsb0]/0], points 0]Â1])
         for i in range(3, len(points), 3):
             bezier.addCoordinates(self.bezier_coords(pointsÂi - 3 : i + 1]))
             bezier.addCoordinate(pointsÂi] 0], pointsei]Â1])
         self.pyoutput(bezier)
 
     def close(self):
         pass

 

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