calculating polygon from points



  • On 22/08/2017 at 12:14, xxxxxxxx wrote:

    Hello PluginCafe,

    I have written a small script, which creates supershapes (based on a sphere).
    So far so good, I can calculate all the points of my object but I don't know why,
    but when it comes to calculating the polygons I just don't get it right.
    I know this is not that sdk related or anything, but it's my first time building an object
    and it would help me for future reference aswell.

    import c4d
    import math
    from c4d import gui
    #Welcome to the world of Python
      
    #constants
    a = 1
    b = 1
    m = 0
    n1 = 1
    n2 = 1
    n3 = 1
      
    def supershapeRAD(theta, m, n1, n2, n3) :
        """Calculates the radius of the supershape from a given theta (lon/lat) and some defined constants"""
        t1 = math.fabs((1/a)*math.cos(m*theta/4))
        t1 = math.pow(t1, n2)
        t2 = math.fabs((1/b)*math.sin(m*theta/4))
        t2 = math.pow(t2, n3)
        t3 = t1+t2
        r = math.pow(t3, -1/n1)
        return r
      
    def main() :
           
        total = 20 # number of points
        rad = 200 #base radius of the sphere
      
        obj = c4d.PolygonObject(total*total, total*total) #create a new polygon object
        
        counter = 0 #counter for polygons
        for i in xrange(total-1) :
            lat = c4d.utils.RangeMap(i, 0, total, -math.pi/2, math.pi/2, False) #map latitude to -pi/2  pi/2
            r2 = supershapeRAD(lat, m, n1, n2, n3) #calculate first supershape radius
            for j in xrange(total) :
                lon = c4d.utils.RangeMap(j, 0, total, -math.pi, math.pi, False)  #map londitude to -pi  pi
                r1 = supershapeRAD(lon, m, n1, n2, n3) #calculate second supershape radius
                
                #calculate position (x,y,z) of the points
                x = rad *r1* math.cos(lon) * r2*math.cos(lat)
                y = rad *r1* math.sin(lon) * r2*math.cos(lat)
                z = rad *r2* math.sin(lat)
                
                obj.SetPoint(j+i*total, c4d.Vector(x,y,z)) #set the point
                   
                #This is the part that gives me trouble
                #obj.SetPolygon(counter, c4d.CPolygon(a,b,c))
                
                counter += 1
                
                
        obj.Message(c4d.MSG_UPDATE)
        doc.InsertObject(obj)
        c4d.EventAdd()
       
    if __name__=='__main__':
        main()
    

    This is my current code, it is able to calculate the necessary points.
    I have already looked into the PyRoundedTube example, but that doesn't really help me.

    I hope somebody can help me, because I feel really stupid right now

    greetings,
    Florian



  • On 23/08/2017 at 07:48, xxxxxxxx wrote:

    Hi Florian,

    I'm not sure about the actual question.
    Basically the CPolygon contains the indexes of points in a left handed order. So you wouldn't call SetPolygon() for every point, but only for a group of points belonging to the polygon (probably just an indentation issue in your code snippet).
    I leave the question which points belong to a polygon in your algorithm to the community.



  • On 23/08/2017 at 08:53, xxxxxxxx wrote:

    Can sound stupid but does the R19 reconstruction feature will be able to input point cloud (list of vectors) and then output a mesh(list of CPolygon)? Since reconstruction feature, seem to take a video as input, I'm pretty sure c4d build a point cloud from this and then perform the reconstruction. It will be awesome and allow a bunch of new things for 3d scanning inside c4d !

    Btw I know you are not allowed to talk explicitly about new features and things like that, then take it as a suggestion ;)

    Anyway regarding op problem I guess this script for blender can help you !
    http://wiki.theprovingground.org/blender-py-supershape



  • On 23/08/2017 at 09:05, xxxxxxxx wrote:

    Hey Adnreas,

    my problem wasn't the CPolygon object, but how to correctly calculate the points for the polygon.

    cheers,
    Florian



  • On 23/08/2017 at 09:21, xxxxxxxx wrote:

    Hey gr4ph0s,

    thanks for the link, I managed to calculate the polygons correctly, thank you very much!

    greetings,
    Florian


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