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# Blender plugin for generating celtic knot curves from 3d meshes
# See README for more information
#
# The MIT License (MIT)
#
# Copyright (c) 2013 Adam Newgas
#
# 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.
bl_info = {
"name": "Celtic Knot",
"description": "",
"author": "Adam Newgas",
"version": (0, 1, 1),
"blender": (2, 74, 0),
"location": "View3D > Add > Curve",
"warning": "",
"wiki_url": "https://github.com/BorisTheBrave/celtic-knot/wiki",
"category": "Add Curve"}
import bpy
import bmesh
from collections import defaultdict
from mathutils import Vector
from math import pi, sin, cos
class CelticKnotOperator(bpy.types.Operator):
bl_idname = "curve.celtic_links"
bl_label = "Celtic Links"
bl_description = 'Select low poly Mesh Object to cover with Knitted Links'
bl_options = {'REGISTER', 'UNDO', 'PRESET'}
weave_up = bpy.props.FloatProperty(name="Weave Up",
description="Distance to shift curve upwards over knots",
subtype="DISTANCE",
unit="LENGTH")
weave_down = bpy.props.FloatProperty(name="Weave Down",
description="Distance to shift curve downward under knots",
subtype="DISTANCE",
unit="LENGTH")
handle_types = [("ALIGNED", "Aligned", "Points at a fixed crossing angle"),
("AUTO", "Auto", "Automatic control points")]
handle_type = bpy.props.EnumProperty(items=handle_types,
name="Handle Type",
description="Controls what type the bezier control points use",
default="AUTO")
crossing_angle = bpy.props.FloatProperty(name="Crossing Angle",
description="Aligned only: the angle between curves in a knot",
default=pi / 4,
min=0, max=pi / 2,
subtype="ANGLE",
unit="ROTATION")
crossing_strength = bpy.props.FloatProperty(name="Crossing Strength",
description="Aligned only: strenth of bezier control points",
soft_min=0,
subtype="DISTANCE",
unit="LENGTH")
handle_type_map = {"AUTO": "AUTOMATIC", "ALIGNED": "ALIGNED"}
geo_bDepth = bpy.props.FloatProperty(
name="Bevel Depth",
default=0.04,
min=0, soft_min=0,
description="Bevel Depth",
)
@classmethod
def poll(cls, context):
ob = context.active_object
# return True
return ((ob is not None) and
(ob.mode == "OBJECT") and
(ob.type == "MESH") and
(context.mode == "OBJECT"))
def execute(self, context):
# Cache some values
s = sin(self.crossing_angle) * self.crossing_strength
c = cos(self.crossing_angle) * self.crossing_strength
handle_type = self.handle_type
weave_up = self.weave_up
weave_down = self.weave_down
# Create the new object
orig_obj = obj = context.active_object
curve = bpy.data.curves.new("Celtic", "CURVE")
curve.dimensions = "3D"
curve.twist_mode = "MINIMUM"
curve.fill_mode = "FULL"
curve.bevel_depth = 0.015
curve.extrude = 0.003
curve.bevel_resolution = 4
obj = obj.data
midpoints = []
# Compute all the midpoints of each edge
for e in obj.edges.values():
v1 = obj.vertices[e.vertices[0]]
v2 = obj.vertices[e.vertices[1]]
m = (v1.co + v2.co) / 2.0
midpoints.append(m)
bm = bmesh.new()
bm.from_mesh(obj)
# Stores which loops the curve has already passed through
loops_entered = defaultdict(lambda: False)
loops_exited = defaultdict(lambda: False)
# Loops on the boundary of a surface
def ignorable_loop(loop):
return len(loop.link_loops) == 0
# Starting at loop, build a curve one vertex at a time
# until we start where we came from
# Forward means that for any two edges the loop crosses
# sharing a face, it is passing through in clockwise order
# else anticlockwise
def make_loop(loop, forward):
current_spline = curve.splines.new("BEZIER")
current_spline.use_cyclic_u = True
first = True
# Data for the spline
# It's faster to store in an array and load into blender
# at once
cos = []
handle_lefts = []
handle_rights = []
while True:
if forward:
if loops_exited[loop]:
break
loops_exited[loop] = True
# Follow the face around, ignoring boundary edges
while True:
loop = loop.link_loop_next
if not ignorable_loop(loop):
break
assert loops_entered[loop] == False
loops_entered[loop] = True
v = loop.vert.index
prev_loop = loop
# Find next radial loop
assert loop.link_loops[0] != loop
loop = loop.link_loops[0]
forward = loop.vert.index == v
else:
if loops_entered[loop]:
break
loops_entered[loop] = True
# Follow the face around, ignoring boundary edges
while True:
v = loop.vert.index
loop = loop.link_loop_prev
if not ignorable_loop(loop):
break
assert loops_exited[loop] == False
loops_exited[loop] = True
prev_loop = loop
# Find next radial loop
assert loop.link_loops[-1] != loop
loop = loop.link_loops[-1]
forward = loop.vert.index == v
if not first:
current_spline.bezier_points.add()
first = False
midpoint = midpoints[loop.edge.index]
normal = loop.calc_normal() + prev_loop.calc_normal()
normal.normalize()
offset = weave_up if forward else weave_down
midpoint = midpoint + offset * normal
cos.extend(midpoint)
if handle_type != "AUTO":
tangent = loop.link_loop_next.vert.co - loop.vert.co
tangent.normalize()
binormal = normal.cross(tangent).normalized()
if not forward:
tangent *= -1
s_binormal = s * binormal
c_tangent = c * tangent
handle_left = midpoint - s_binormal - c_tangent
handle_right = midpoint + s_binormal + c_tangent
handle_lefts.extend(handle_left)
handle_rights.extend(handle_right)
points = current_spline.bezier_points
points.foreach_set("co", cos)
if handle_type != "AUTO":
points.foreach_set("handle_left", handle_lefts)
points.foreach_set("handle_right", handle_rights)
# Attempt to start a loop at each untouched loop in the entire mesh
for face in bm.faces:
for loop in face.loops:
if ignorable_loop(loop):
continue
if not loops_exited[loop]:
make_loop(loop, True)
if not loops_entered[loop]:
make_loop(loop, False)
# Create an object from the curve
from bpy_extras import object_utils
object_utils.object_data_add(context, curve, operator=None)
# Set the handle type (this is faster than setting it pointwise)
bpy.ops.object.editmode_toggle()
bpy.ops.curve.select_all(action="SELECT")
bpy.ops.curve.handle_type_set(type=self.handle_type_map[handle_type])
# Some blender versions lack the default
bpy.ops.curve.radius_set(radius=1.0)
bpy.ops.object.editmode_toggle()
# Restore active selection
curve_obj = context.active_object
context.scene.objects.active = orig_obj
# If thick, then give it a bevel_object and convert to mesh
return {'FINISHED'}
def menu_func(self, context):
self.layout.operator(CelticKnotOperator.bl_idname,
text="Celtic Knot From Mesh",
icon='PLUGIN')
def register():
bpy.utils.register_module(__name__)
bpy.types.INFO_MT_curve_add.append(menu_func)
def unregister():
bpy.types.INFO_MT_curve_add.remove(menu_func)
bpy.utils.unregister_module(__name__)
if __name__ == "__main__":
register()