Move polygon along normal
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On 28/03/2013 at 11:26, xxxxxxxx wrote:
I want to move a polygon along its normal (normal move).
So I calculate the cross vector of the polygon using two sides as vector.
However, when I compare my result with the result of the Xpresso' polygon node - polygon normal' it is different. But the point normal from the Point node is the same as the cross vector I calculate.
Strange?Is the point normal different then the polygon normal?
Also when I start moving the polygon, my calculation seems to go wrong.
I expect that my calculation of the cross vector is wrong.I get all the polygon points, normalize them and use them to calculate the vectors.
This might be wrong, because I do not include the starting point?Note: There is only one polygon in my polygon object.
I do not want to use the cinema 4d 'move normal' command.import c4d from c4d import utils import random # # move polygon along its normal # def main() : polyobject = doc.SearchObject("MyObject") polys = polyobject.GetAllPolygons() p1 = polyobject.GetPoint(polys[0].a) p2 = polyobject.GetPoint(polys[0].b) p3 = polyobject.GetPoint(polys[0].c) p4 = polyobject.GetPoint(polys[0].d) print p1,p2,p3,p4 np1 = p1.GetNormalized() np2 = p2.GetNormalized() np3 = p3.GetNormalized() np4 = p4.GetNormalized() p1p2 = (np2-np1) p1p3 = (np3-np1) pcross = p1p2.Cross(p1p3) pcross = pcross.GetNormalized() print "cross: ", pcross -
On 28/03/2013 at 11:37, xxxxxxxx wrote:
cpoly = polygonObject.GetPolygon(id)
nrm = ((cpoly.a - cpoly.b) % (cpoly.a - cpoly.d)).GetNormalized() -
On 28/03/2013 at 11:44, xxxxxxxx wrote:
For a cube, I get Vector(0, 0, -1) which is correct. Btw, a bit shorter:
def main() : p = op.GetPolygon(0) points = op.GetAllPoints() p1, p2, p4 = points[p.a], points[p.b], points[p.d] print (p2 - p1).Cross(p4 - p1).GetNormalized() main()Note that you need to take the forth point into account instead of the third, which might
be the cause why you get "wrong values". -
On 28/03/2013 at 11:47, xxxxxxxx wrote:
lol, i forgot to access the vectors, cpolys just contains the ids , doh, i am a it dizzy, just
follow nikklas
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On 28/03/2013 at 11:49, xxxxxxxx wrote:
I just checked the polygon-node in XPresso and it gives the same result.
@Ferdinand: You also computed the inversed normal. It's (B - A) cross (D - A) to compute
the correct normal.
Ehrm wait, I thought that it would be.. but it isn't? Just checked.. Gonna think about that
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On 28/03/2013 at 13:49, xxxxxxxx wrote:
Originally posted by xxxxxxxx
For a cube, I get Vector(0, 0, -1) which is correct. Btw, a bit shorter:
def main() : p = op.GetPolygon(0) points = op.GetAllPoints() p1, p2, p4 = points[p.a], points[p.b], points[p.d] print (p2 - p1).Cross(p4 - p1).GetNormalized() main()Note that you need to take the forth point into account instead of the third, which might
be the cause why you get "wrong values".Brilliant again, thanks.
Indeed using p4, I do not get 'wrong values'.Here the code to get the polygon moving along the normal.
Just add it to all the points of the polygon and do an update.Note: the calculated cross is now the same as the Xpresso one and Xpresso point normal is the same as the polygon normal.
import c4d from c4d import utils import random # # move polygon along its normal # def main() : frame = doc.GetTime().GetFrame(doc.GetFps()) if (frame >= 5) : polyobject = doc.SearchObject("MyObject") p = polyobject.GetPolygon(0) #get polygon points = polyobject.GetAllPoints() #get all points p1, p2, p3, p4 = points[p.a], points[p.b], points[p.c], points[p.d] pcross = (p2 - p1).Cross(p4 - p1).GetNormalized() print pcross p1 = p1 + pcross p2 = p2 + pcross p3 = p3 + pcross p4 = p4 + pcross #print p1,p2,p3,p4 p1 = polyobject.SetPoint(p.a,p1) p2 = polyobject.SetPoint(p.b,p2) p3 = polyobject.SetPoint(p.c,p3) p4 = polyobject.SetPoint(p.d,p4) polyobject.Message (c4d.MSG_UPDATE) c4d.EventAdd()