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Cinema 4D - Python version of my Select Loop plugin
"""
This is a python port of my old Select Loop C++ plugin for Cinema 4D. Rather
than porting this to R20 and recompiling, distributing, etc I decided to port
it to Python for use as a Script manager plugin.
Just import this script into your Script Manager and add it to a toolbar
or assign a shortcut.
MIT License
Copyright 2019 Christopher Montesano
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is furnished
to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
"""
import c4d
from c4d.utils import Neighbor
from c4d import gui
def get_opposite_edge(poly, p1, p2):
if (p1 == p2):
return None
if (poly.c == poly.d): # triangle
return None
points = (p1, p2)
if poly.a in points and poly.b in points:
return poly.c, poly.d
if poly.b in points and poly.c in points:
return poly.a, poly.d
if poly.c in points and poly.d in points:
return poly.a, poly.b
if poly.d in points and poly.a in points:
return poly.b, poly.c
return None
def get_shared_points(poly1, poly2):
shared_points = set()
for pta in (poly1.a, poly1.b, poly1.c, poly1.d):
for ptb in (poly2.a, poly2.b, poly2.c, poly2.d):
if pta == ptb:
shared_points.add(pta)
return list(shared_points)
def select_poly_loop(obj, nth=1, sim=False):
if obj is None:
raise ValueError("No object selected")
if not isinstance(obj, c4d.PolygonObject):
raise ValueError("Not a polygon object")
cply = obj.GetPolygonCount()
cpnt = obj.GetPointCount()
bsel = obj.GetPolygonS()
if cply == 0:
raise ValueError("No polygons found")
if bsel.GetCount() != 2:
raise ValueError("Exactly two polygons must be selected")
plys = obj.GetAllPolygons()
selected_ids = []
for index, selected in enumerate(bsel.GetAll(cply)):
if not selected:
continue
selected_ids.append(index)
assert(len(selected_ids) == 2)
poly1 = plys[selected_ids[0]]
poly2 = plys[selected_ids[1]]
shared_points = get_shared_points(poly1, poly2)
if len(shared_points) != 2:
raise ValueError("Selected polygons must share an edge")
n = Neighbor()
n.Init(obj)
for poly_index in range(2):
this_poly_index = selected_ids[poly_index]
pt1 = shared_points[0]
pt2 = shared_points[1]
for i in range(cply):
nply = n.GetNeighbor(pt1, pt2, this_poly_index)
if nply is None:
break
this_poly_index = nply
bsel.Select(nply)
if i % nth != 0:
bsel.Toggle(nply)
opposite_edge = get_opposite_edge(plys[this_poly_index], pt1, pt2)
if opposite_edge is None:
break
pt1, pt2 = opposite_edge
if pt1 == shared_points[0] and pt2 == shared_points[1]:
break
obj.Message(c4d.MSG_CHANGE)
c4d.EventAdd()
def main():
nth = gui.InputDialog("Select every nth polygon:", "1")
nth = int(nth)
try:
select_poly_loop(op, nth)
except ValueError as err:
gui.MessageDialog(str(err))
if __name__=='__main__':
main()
@favourizo

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favourizo commented Jan 31, 2020

Hi there, thanks for your code.

I can't seem to get mine to work, I always get the error the selected polygons must share an edge. And I want to select every 1&3rd polygons.

Please can you get back to me soon

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cmontesano commented Feb 1, 2020

Make sure that you are selecting two polygons that are touching. They need to share exactly two points. If you already have two polygons selected that appear to be touching then you might have disconnected geometry. Running an optimize command might help.

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favourizo commented Feb 1, 2020

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cmontesano commented Feb 1, 2020

It needs those two touching polygons to determine the loop direction. If you select "2" (every other polygon) or "3" (every 3rd polygon) it will deselect one of the neighboring polygons.
If you select two neighboring polygons and choose a number greater than one you should get a pretty good idea for how it works.

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favourizo commented Feb 2, 2020

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favourizo commented Feb 2, 2020

@Hansimov

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Hansimov commented Mar 4, 2020

Thanks for your amazing contribution!
I modify the script a bit to:

  1. Support jumping select points of Spline object, according to this link
  2. Support selecting multiple loops with offsets, e.g., when nth is 5, you can select all polygons whose idx (% nth) are in [0,2,3].
  3. Fix IndexError when using GetNeighbor on plane object polygons

The most recently updated version of this script could be found here since I might not update it here in time.

"""
Jump Select
(Original name: Select Loop)
MIT License
Copyright 2019 Christopher Montesano
Modified by Hansimov, 2020.03
"""

import c4d
from c4d.utils import Neighbor
from c4d import gui

def get_opposite_edge(poly, p1, p2):
    if (p1 == p2) or (poly.c == poly.d):
        return None

    points = (p1, p2)
    poly_abcd = [poly.a, poly.b, poly.c, poly.d]
    poly_oppo = []

    for ele in poly_abcd:
        if ele not in points:
            poly_oppo.append(ele)

    if poly_oppo != []:
        return poly_oppo[:2]
    else:
        return None

def get_shared_points(poly1, poly2):
    shared_points = set()
    for pta in (poly1.a, poly1.b, poly1.c, poly1.d):
        for ptb in (poly2.a, poly2.b, poly2.c, poly2.d):
            if pta == ptb:
                shared_points.add(pta)
    return list(shared_points)

def select_poly_loop(obj, nth, sim=False):
    if obj is None:
        raise ValueError("No object selected")

    if not isinstance(obj, c4d.PolygonObject):
        raise ValueError("Not a polygon object")

    cply = obj.GetPolygonCount()
    cpnt = obj.GetPointCount()
    bsel = obj.GetPolygonS()

    if cply == 0:
        raise ValueError("No polygons found")
    if bsel.GetCount() != 2:
        raise ValueError("Must select if and only if 2 edges!")

    offsets = get_offsets(nth)

    plys = obj.GetAllPolygons()

    selected_ids = []
    for index, selected in enumerate(bsel.GetAll(cply)):
        if not selected:
            continue
        selected_ids.append(index)

    assert(len(selected_ids) == 2)

    poly1 = plys[selected_ids[0]]
    poly2 = plys[selected_ids[1]]

    shared_points = get_shared_points(poly1, poly2)
    if len(shared_points) != 2:
        raise ValueError("Selected polygons must share an edge!")

    n = Neighbor()
    n.Init(obj)

    for poly_index in range(2):
        this_poly_index = selected_ids[poly_index]
        pt1 = shared_points[0]
        pt2 = shared_points[1]

        for i in range(cply):
            try:
                nply = n.GetNeighbor(pt1, pt2, this_poly_index)
            # This IndexError happens on `plane` object polygons
            except IndexError as err:
                gui.MessageDialog("IndexError of GetNeighbor!")
                break

            if nply in [None,-1]:
                break

            this_poly_index = nply
            bsel.Select(nply)
            if not i%nth in offsets:
                bsel.Toggle(nply)
            opposite_edge = get_opposite_edge(plys[this_poly_index], pt1, pt2)
            if opposite_edge is None:
                break
            pt1, pt2 = opposite_edge
            if pt1 == shared_points[0] and pt2 == shared_points[1]:
                break

    obj.Message(c4d.MSG_CHANGE)
    c4d.EventAdd()

def select_spline_point_loop(op,nth):
    sel = op.GetPointS()
    sel.DeselectAll()
    cnt = op.GetPointCount()
    offsets = get_offsets(nth)
    for i in range(cnt):
        if i%nth in offsets: sel.Select(i)
    c4d.EventAdd()

def get_offsets(nth):
    if nth == 1:
        return [0]
    offset_list = gui.InputDialog("Set offsets (int, 0-{}), use space to split several offsets".format(nth-1), "1")
    offset_list = offset_list.split()
    offsets = []
    for offset in offset_list:
        offsets.append(min(int(offset),nth-1))
    return offsets

def main():
    op = doc.GetActiveObject()
    if not op:
        gui.MessageDialog("No active object!", c4d.GEMB_ICONSTOP)
        return False

    if type(op) == c4d.PolygonObject:
        nth = int(gui.InputDialog("Set nth (int) of polys:", "2"))
        try:
            select_poly_loop(op, nth)
        except ValueError as err:
            gui.MessageDialog(str(err), c4d.GEMB_ICONSTOP)
    elif type(op) == c4d.SplineObject:
        nth = int(gui.InputDialog("Set nth (int) of points:", "2"))
        try:
            select_spline_point_loop(op,nth)
        except ValueError as err:
            gui.MessageDialog(str(err), c4d.GEMB_ICONSTOP)
    else:
        return False

if __name__=='__main__':
    main()
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cmontesano commented Mar 4, 2020

Nice update, and good catch on the IndexError. I expect that would happen when it reaches a boundary of a broken loop.

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