[PyOpenGL-Users] Pyopengl - slow performance using

[<pm...@gm...>]

Hi all,

I am developing an application using pyopenGL to read data from a shape file and to draw it in 2D using openGl. However, the performance is really bad; it takes up to 20 seconds to draw the map. I am using Ubuntu and nVidia NVS 3100M.

The shape file being read has the following characteristics:

- 50 000 entries containing the description roads segments; each road segment has the associated geometry (set of (x,y) points ) 
- +/- 350 000 points in total


A simplified version of the code is shown bellow:

a) to get data from shapefile (using pyshapelib) and store it in a list of lists of tuples (python):
        ...
        self.shp = []
        self.extents = []
        self.array = []
        ...
        self.shp = shapelib.ShapeFile(filename)
        for i in range(self.shp.info()[0]):
            lineVert = self.shp.read_object(i).vertices()
            tempArray = []
            for j in lineVert[0]:
                tempArray.append([j[0],j[1]])
            self.array.append(tempArray)

b) to draw the data using pyopenGL:
        ...
        glEnableClientState(GL_VERTEX_ARRAY)
        # obtained from the shapefile(array element)
        arrayList = self.map.getArrayList() 
        if len(arrayList) > 0:
            for objMap in arrayList:
                self.drawPolyline(objMap)

     def drawPolyline(self,inArray):
        #glColor(1.0, 0.0, 0.0)
        glVertexPointerf(inArray)
        glDrawArrays(GL_LINE_STRIP, 0, len(inArray))

- Do you have any hints how to improve the performance dramatically and make it usable? I tried several options but none worked out. For instance I tried to replace python list with numpy arrays but the performance was not significantly changed.

- Do I need execute the OpenGL code in C? Altough I could do this, I still need to use python as scripting language due to other dependencies of the implementation.

Thank you in advance for your help!

Best Regards,

Pedro

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