There is another problem in the last script ; the arrows appear but the curve are not appear in grasshopper
emm thats wird ; it work in a new document
I haven’t tested the script, but it also needs to compute the bounding box of all the geometry that it wants to preview. Then, the bounding box must be returned in the get_ClippingBox method. As it is shown here:
I moved this sub-topic to a new topic.
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Many thanks Giulio, i appreciate your help
i study now when many curves selected
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My Brain stopped here 
from ghpythonlib.componentbase import executingcomponent as component
import System
import rhinoscriptsyntax as rs
import Rhino.Geometry as rg
class PreviewEx(component):
def RunScript(self,C):
self.crv = C
if not self.crv: return
self.points = []
self.tgnt = []
for i in range(len(C)):
pts = rs.DivideCurve(self.crv[i],2,True)
for j in range(3):
pt = rs.CurveClosestPoint(self.crv[i],pts[j])
tg = rs.CurveTangent(self.crv[i],pt)
self.tgnt.append(tg)
self.points.append(pts[j])
#print self.points
#print self.tgnt
def DrawViewportWires(self,arg):
if not self.crv: return
for i in range(len(self.crv)):
for i in range(3):
arg.Display.DrawDirectionArrow(self.points[i], self.tgnt[i], System.Drawing.Color.White)
the input have two curves (or more )
in def DrawViewportWires(self,arg): the length of curves list have no effect
maybe because i append all points and tangents
I compile the script and it work fine with single curve without bounding box
One day it might not work fine. This is a requirement that does not show sometimes. But then when it shows, it is really bad. I also don’t see the point of compiling if the code is already online…
My 2 cents.
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I compile it to try if it work because sometimes the scripts it work fine but after compiling nope.
and of course i need the best solution that why i asked and i don’t really understand the idea of the bounding box, i will study it more.
I use always examples from help but some of them don’t work or need more lines to work
The bounding box computation is because of this: Rhino tries to optimize preview by using bounding boxes. If the thing that you want to draw is outside the “view frustum”, then its drawing function will not be called. This operation is called “view frustum culling”.
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Thank you ,I tried it but bounding box union don’t accept the points
Update:
i use this ; i don’t know if this work or not
i hope this ok 
, thanks for help Giulio
from ghpythonlib.componentbase import executingcomponent as component
import Grasshopper, GhPython
import System
import Rhino
import rhinoscriptsyntax as rs
import Rhino.Geometry as rg
class DisplayDirection(component):
def __init__(self):
self.pts = []
self.bb = Rhino.Geometry.BoundingBox()
def RunScript(self,C):
self.c = C
if not self.c: return
self.bb = Rhino.Geometry.BoundingBox()
self.tps = []
self.tgnt = []
self.pts = rs.DivideCurve(self.c,2,True)
for i in range(len(self.pts)):
self.bb.Union(self.pts[i])
self.pts.insert(2, rs.CurveEndPoint(self.c))
for i in range(3):
pt = rs.CurveClosestPoint(self.c,self.pts[i])
self.tps.append(pt)
tg = rs.CurveTangent(self.c,self.tps[i])
self.tgnt.append(tg)
def DrawViewportWires(self,arg):
if not self.c: return
for i in range(3):
arg.Display.DrawDirectionArrow(self.pts[i], self.tgnt[i], System.Drawing.Color.White)
def get_ClippingBox(self):
return self.bbUpdate: this version work with multi curves, i also add the idea of bounding box
i know there is always more simple method but that what i get
from ghpythonlib.componentbase import executingcomponent as component
import Grasshopper, GhPython
import System
import Rhino
import rhinoscriptsyntax as rs
class CurvesDirection(component):
def __init__(self):
self.pts = []
self.bb = Rhino.Geometry.BoundingBox()
def RunScript(self, C):
self.c = C
if not self.c: return
self.bb = Rhino.Geometry.BoundingBox()
lisc = []
self.plist = []
self.tlist = []
for i in range(len(self.c)):
lisc.append([self.c[i]])
for i in range(len(self.c)):
if not self.c[i] : return
if rs.IsCurveClosed(self.c[i]) == True:
n = 3
elif rs.IsCurveClosed(self.c[i]) == False:
n = 2
for j in range(1):
self.pt = rs.DivideCurve(lisc[i][0],n,True)
for k in range(len(self.pt)):
self.bb.Union(self.pt[k])
self.pts = rs.CurveClosestPoint(self.c[i],self.pt[k])
self.tg = rs.CurveTangent(self.c[i],self.pts)
self.plist.append(self.pt[k])
self.tlist.append(self.tg)
parts = len(self.c)
self.p = [self.plist[(i*len(self.plist))//parts:((i+1)*len(self.plist))//parts] for i in range(parts)]
self.t = [self.tlist[(i*len(self.plist))//parts:((i+1)*len(self.plist))//parts] for i in range(parts)]
def DrawViewportWires(self,arg):
if not self.c: return
for i in range(len(self.c)):
if not self.c[i] : return
for j in range(3):
arg.Display.DrawDirectionArrow(self.p[i][j],self.t[i][j], System.Drawing.Color.White)
def get_ClippingBox(self):
return self.bbIt work fine now i hope no problem appear in future
I create also other components i need them
Thank you for help
Hi Seghier
Care to share?
Yes of course; if a problem appear tell me
Lovely! Appreciate it.
I fix one problem ; Analyse direction create points
Please remove the old one
Analyse Direction.ghpy (33.5 KB)
components.zip (29.8 KB)
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Thanks!
In “Vipers” is a component that can do the arrow preview of a curve direction. I’m using that quite often.
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Nice but i can’t spend time translate and try to find what their components do !
This components are translated. Just need to check the github page and download the right zip file.
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