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cae-tools/sfc/slicer.py

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#!/usr/bin/python
#
# slicer.py - FreeCAD-based STL to Gnuplot slicer
#
# Written 2015 by Werner Almesberger
# Copyright 2015 by Werner Almesberger
#
# This program//library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
import sys
sys.path.append("/usr/lib/freecad/lib")
import FreeCAD, Part, Mesh
import os, getopt
from FreeCAD import Base
from math import hypot
epsilon = 0.0001 # acceptable math rounding error and slicing offset
mech_eps = 0.01 # acceptable mechanical deviation
margin = None # draw a rectangular workpiece at the specified xy
# distance around the model (default: none)
z_step = None # maximum Z step (default: unlimited)
flip = False # flip around X center (default: don't)
height = None # height of the workpiece above the Z plane (can be
# negative). Default: use model dimensions.
align_top = None # align the Z position of the model to the workpiece
align_bottom = None
end = 0 # Z adjustment of final layer
def dist(a, b):
pa = a.Point
pb = b.Point
return hypot(pa[0] - pb[0], pa[1] - pb[1])
def print_vec(v, z):
p = v.Point
print p[0], " ", p[1], " ", z
# Make a vector from a point. While we're at it, also apply flipping (if
# requested).
def vec(p):
if flip:
return Base.Vector(p[0],
bb.YMax - p[1] + bb.YMin, bb.ZMax - p[2] + bb.ZMin)
else:
return Base.Vector(p[0], p[1], p[2])
#
# Dump the current Z level (plateau or intermediate level).
#
def dump_level(wires, z):
print "# level z = ", z
if margin is not None:
print bb.XMin - margin, " ", bb.YMin - margin, " ", z
print bb.XMax + margin, " ", bb.YMin - margin, " ", z
print bb.XMax + margin, " ", bb.YMax + margin, " ", z
print bb.XMin - margin, " ", bb.YMax + margin, " ", z
print bb.XMin - margin, " ", bb.YMin - margin, " ", z
print
for wire in wires:
print "# wire = ", wire
first = None
last = None
for e in wire.Edges:
v = e.Vertexes[0]
if first is None:
first = v
if last is None or dist(v, last) >= mech_eps:
print_vec(v, z)
last = v
if first is not None:
print_vec(first, z)
print
print
def usage():
print >>sys.stderr, "usage:", sys.argv[0], \
"[-a (top|bottom)(+|-)offset] [-f] [-h height]\n" + \
"\t[-m tolerance] [-p piece_distance] [-o z_offset] "+ \
"[-s max_step] file.stl"
sys.exit(1)
#
# FreeCAD prints progress information to stdout instead of stderr.
# We don't want that ...
#
stdout = os.dup(1)
os.dup2(2, 1)
sys.stdout = os.fdopen(stdout, "w")
opts, args = getopt.getopt(sys.argv[1:], "a:e:fh:m:o:p:s:")
for opt, arg in opts:
if opt == "-a":
if arg[0:3] == "top":
align_top = float(arg[3:])
elif arg[0:6] == "bottom":
align_bottom = float(arg[6:])
else:
usage()
elif opt == "-m":
mech_eps = float(arg)
elif opt == "-o":
end = float(arg)
elif opt == "-f":
flip = True
elif opt == "-h":
height = float(arg)
elif opt == "-p":
margin = float(arg)
elif opt == "-s":
z_step = float(arg)
else:
assert False
if len(args) != 1:
usage()
#
# Read the STL mesh and determine its bounding box
#
mesh = Mesh.Mesh(args[0])
bb = mesh.BoundBox
#
# The 2.5D model consists of "plateaus" (facets parallel to the xy plane) and
# "walls" (facets parallel to the z axis). Anything else is an error and will
# produce incorrect results.
#
# We use plateau facets only for their z position, as indication where to mill
# a plateau. Wall facets are kept for later use.
#
vert = Mesh.Mesh()
z_raw = {}
max_nz = 0
inclined = 0
for facet in mesh.Facets:
if abs(facet.Normal.z) >= 1 - epsilon:
z = facet.Points[0][2]
if flip:
z = bb.ZMax - z + bb.ZMin
z_raw[z] = 1
else:
nz = abs(facet.Normal.z)
if nz > epsilon:
inclined += 1
max_nz = max(max_nz, nz)
vert.addFacet(vec(facet.Points[0]), vec(facet.Points[1]),
vec(facet.Points[2]))
if inclined:
print >>sys.stderr # FreeCAD progress reporting messes up newlines
print >>sys.stderr, inclined, "inclined facets, maximum normal", max_nz
#
# @@@ This is perhaps a bit too paranoid
#
# I wrote the Z noise filtering because I had mis-read perfectly good
# distinct coordinates as being essentially the same value but with
# rounding errors.
#
z_levels = []
last = None
for z in sorted(z_raw.keys(), reverse = True):
if last is None or last - z > epsilon:
z_levels.append(z)
last = z
#
# Convert the walls to a FreeCAD shape
#
shape = Part.Shape()
shape.makeShapeFromMesh(vert.Topology, mech_eps)
z_off = 0
if height is not None:
if align_top is not None:
z_off = align_top - bb.ZMax
if height > 0:
z_off += height
if align_bottom is not None:
z_off = align_bottom - bb.ZMin
if height < 0:
z_off += height
#
# Iterate over all plateaus and determine how they intersect with the walls.
# For this, we add a small offset to the z position so that we intersect above
# the plateau.
#
# We advance by at most z_step and insert intermediate layers if needed.
#
if height is not None and height > 0:
last_z = height - z_off
else:
last_z = None
if height is not None and height < 0 and z_levels[-1] > height:
z_levels.append(height - z_off)
for i in range(0, len(z_levels)):
next_z = z_levels[i]
wires = shape.slice(Base.Vector(0, 0, 1), next_z + epsilon)
if i == len(z_levels) - 1:
next_z += end
if z_step is None or last_z is None or last_z - z_step <= next_z:
dump_level(wires, next_z + z_off)
else:
d = last_z - next_z
n = int(d // z_step) + 1
for j in range(0, n):
dump_level(wires, last_z - (j + 1) * (d / n) + z_off)
last_z = next_z
#
# That's all, folks !
#