I want to convert this grasshopper script to python. I want very minimal python libraries. I want a requirements.txt. a venv to install in and use pip3 in in macos. I want a gui, with trimesh,tkinter, shapely, numpy ezdxf and something to write svg files. use tkinter drag and drop to be able to add files. and show a preview. tabs worked ok at 0.7mm and layers for paper were thickness 0.4 maybe or card 1.1mm or mdf 2.5mm.
Make an install method (maybe script), make a python script, make a venv (maybe a install script that has security chmod step, an option, "make a venv and log in?")
Use as few libraries as possible, maybe like the list above. make run in applet
Don't give preamble, just code and commands and minimal steps

____

```
project/
├── app.py
├── requirements.txt
├── install.sh
├── run.sh
├── input/
├── output/
└── README.md
```

requirements.txt

```
numpy
trimesh
shapely
ezdxf
svgwrite
tkinterdnd2
Pillow
matplotlib
```

install.sh

```
#!/bin/bash

set -e

echo "Creating venv..."
python3 -m venv venv

echo "Activating venv..."
source venv/bin/activate

echo "Upgrading pip..."
pip3 install --upgrade pip

echo "Installing requirements..."
pip3 install -r requirements.txt

echo ""
echo "Done."
echo ""
echo "Run:"
echo "source venv/bin/activate"
echo "python3 app.py"
```

`chmod +x install.sh`

run.sh

```
#!/bin/bash

source venv/bin/activate
python3 app.py
```

app.py

```
import os
import numpy as np
import trimesh
import svgwrite
import tkinter as tk

from tkinter import ttk
from tkinter import filedialog
from tkinterdnd2 import DND_FILES, TkinterDnD

from PIL import Image, ImageTk

import matplotlib
matplotlib.use("Agg")

import matplotlib.pyplot as plt


TAB_WIDTH = 0.7

MATERIALS = {
    "Paper 0.4mm": 0.4,
    "Card 1.1mm": 1.1,
    "MDF 2.5mm": 2.5
}


class SliceApp:

    def __init__(self, root):

        self.root = root
        self.root.title("Paper Slicer")

        self.mesh = None
        self.preview_img = None

        self.build_ui()

    def build_ui(self):

        top = ttk.Frame(self.root)
        top.pack(fill="x", padx=10, pady=10)

        self.material_var = tk.StringVar(value="Card 1.1mm")

        ttk.Label(top, text="Material").pack(side="left")

        ttk.OptionMenu(
            top,
            self.material_var,
            "Card 1.1mm",
            *MATERIALS.keys()
        ).pack(side="left", padx=5)

        ttk.Button(
            top,
            text="Open File",
            command=self.open_file
        ).pack(side="left", padx=5)

        ttk.Button(
            top,
            text="Export SVG",
            command=self.export_svg
        ).pack(side="left", padx=5)

        self.drop = tk.Label(
            self.root,
            text="Drag STL/OBJ here",
            relief="ridge",
            height=5
        )

        self.drop.pack(fill="x", padx=10, pady=10)

        self.drop.drop_target_register(DND_FILES)
        self.drop.dnd_bind("<<Drop>>", self.drop_file)

        self.preview = tk.Label(self.root)
        self.preview.pack(fill="both", expand=True, padx=10, pady=10)

    def open_file(self):

        path = filedialog.askopenfilename(
            filetypes=[
                ("3D files", "*.stl *.obj")
            ]
        )

        if path:
            self.load_mesh(path)

    def drop_file(self, event):

        path = event.data.strip("{}")
        self.load_mesh(path)

    def load_mesh(self, path):

        self.mesh = trimesh.load(path)

        self.make_preview()

    def make_preview(self):

        fig = plt.figure(figsize=(5, 5))
        ax = fig.add_subplot(111, projection="3d")

        vertices = self.mesh.vertices

        ax.scatter(
            vertices[:, 0],
            vertices[:, 1],
            vertices[:, 2],
            s=1
        )

        ax.set_axis_off()

        temp = "preview.png"

        plt.savefig(temp, bbox_inches="tight")
        plt.close(fig)

        img = Image.open(temp)
        img.thumbnail((600, 600))

        self.preview_img = ImageTk.PhotoImage(img)

        self.preview.configure(image=self.preview_img)

    def export_svg(self):

        if self.mesh is None:
            return

        material_thickness = MATERIALS[self.material_var.get()]

        zmin = self.mesh.bounds[0][2]
        zmax = self.mesh.bounds[1][2]

        layers = np.arange(
            zmin,
            zmax,
            material_thickness
        )

        dwg = svgwrite.Drawing(
            "output/slices.svg",
            profile="tiny"
        )

        x_offset = 0

        for z in layers:

            section = self.mesh.section(
                plane_origin=[0, 0, z],
                plane_normal=[0, 0, 1]
            )

            if section is None:
                continue

            planar, tf = section.to_planar()

            for entity in planar.entities:

                pts = planar.vertices[entity.points]

                pts2d = []

                for p in pts:
                    pts2d.append((
                        p[0] + x_offset,
                        p[1]
                    ))

                dwg.add(
                    dwg.polyline(
                        pts2d,
                        stroke="black",
                        fill="none",
                        stroke_width=0.1
                    )
                )

            x_offset += 100

        os.makedirs("output", exist_ok=True)

        dwg.save()

        print("Saved output/slices.svg")


if __name__ == "__main__":

    root = TkinterDnD.Tk()

    app = SliceApp(root)

    root.geometry("800x700")

    root.mainloop()
```

Run:

```
./install.sh
./run.sh
```

Script:

```
cd /FULL/PATH/TO/project
./run.sh
```

Save as `PaperSlicer.app`.

---

plz not use Matplotlib. It says it " is building the font cache; this may take a moment."

remove pillow what is pyglet?

show full code of app.py

---

```
import os
import numpy as np
import trimesh
import svgwrite
import tkinter as tk

from tkinter import ttk
from tkinter import filedialog
from tkinterdnd2 import TkinterDnD, DND_FILES


TAB_WIDTH = 0.7

MATERIALS = {
    "Paper 0.4mm": 0.4,
    "Card 1.1mm": 1.1,
    "MDF 2.5mm": 2.5
}


class SliceApp:

    def __init__(self, root):

        self.root = root
        self.root.title("Paper Slicer")

        self.mesh = None

        self.build_ui()

    def build_ui(self):

        top = ttk.Frame(self.root)
        top.pack(fill="x", padx=10, pady=10)

        self.material_var = tk.StringVar(value="Card 1.1mm")

        ttk.Label(
            top,
            text="Material"
        ).pack(side="left")

        ttk.OptionMenu(
            top,
            self.material_var,
            "Card 1.1mm",
            *MATERIALS.keys()
        ).pack(side="left", padx=5)

        ttk.Button(
            top,
            text="Open File",
            command=self.open_file
        ).pack(side="left", padx=5)

        ttk.Button(
            top,
            text="Export SVG",
            command=self.export_svg
        ).pack(side="left", padx=5)

        self.drop = tk.Label(
            self.root,
            text="Drag STL or OBJ here",
            relief="ridge",
            height=4
        )

        self.drop.pack(
            fill="x",
            padx=10,
            pady=10
        )

        self.drop.drop_target_register(DND_FILES)

        self.drop.dnd_bind(
            "<<Drop>>",
            self.drop_file
        )

        self.canvas = tk.Canvas(
            self.root,
            bg="white"
        )

        self.canvas.pack(
            fill="both",
            expand=True,
            padx=10,
            pady=10
        )

    def open_file(self):

        path = filedialog.askopenfilename(
            filetypes=[
                ("3D files", "*.stl *.obj")
            ]
        )

        if path:
            self.load_mesh(path)

    def drop_file(self, event):

        path = event.data.strip("{}")

        self.load_mesh(path)

    def load_mesh(self, path):

        try:

            self.mesh = trimesh.load(path)

            self.make_preview()

            print(f"Loaded: {path}")

        except Exception as e:

            print("Load error:")
            print(e)

    def make_preview(self):

        self.canvas.delete("all")

        if self.mesh is None:
            return

        verts = self.mesh.vertices
        faces = self.mesh.faces

        w = self.canvas.winfo_width()
        h = self.canvas.winfo_height()

        if w < 10:
            w = 800

        if h < 10:
            h = 600

        x = verts[:, 0]
        y = verts[:, 1]

        xmin = x.min()
        xmax = x.max()

        ymin = y.min()
        ymax = y.max()

        scale = min(
            (w - 100) / (xmax - xmin + 1e-6),
            (h - 100) / (ymax - ymin + 1e-6)
        )

        for face in faces:

            pts = []

            for idx in face:

                px = (x[idx] - xmin) * scale + 50
                py = (y[idx] - ymin) * scale + 50

                py = h - py

                pts.extend([px, py])

            self.canvas.create_polygon(
                pts,
                outline="black",
                fill="",
                width=1
            )

    def export_svg(self):

        if self.mesh is None:
            return

        os.makedirs("output", exist_ok=True)

        material_thickness = MATERIALS[
            self.material_var.get()
        ]

        zmin = self.mesh.bounds[0][2]
        zmax = self.mesh.bounds[1][2]

        layers = np.arange(
            zmin,
            zmax,
            material_thickness
        )

        dwg = svgwrite.Drawing(
            "output/slices.svg",
            profile="tiny"
        )

        x_offset = 0

        for z in layers:

            section = self.mesh.section(
                plane_origin=[0, 0, z],
                plane_normal=[0, 0, 1]
            )

            if section is None:
                continue

            planar, tf = section.to_planar()

            for entity in planar.entities:

                pts = planar.vertices[
                    entity.points
                ]

                pts2d = []

                for p in pts:

                    pts2d.append((
                        p[0] + x_offset,
                        p[1]
                    ))

                dwg.add(
                    dwg.polyline(
                        pts2d,
                        stroke="black",
                        fill="none",
                        stroke_width=0.1
                    )
                )

            x_offset += 100

        dwg.save()

        print("Saved output/slices.svg")


if __name__ == "__main__":

    root = TkinterDnD.Tk()

    root.geometry("1000x700")

    app = SliceApp(root)

    root.mainloop()
```

---

error:

Loaded: /Users/ger/Downloads/3dbenchy.stl
Exception in Tkinter callback
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/tkinter/__init__.py", line 1968, in __call__
    return self.func(*args)
           ^^^^^^^^^^^^^^^^
  File "/Users/ger/Downloads/Fab_Academy/repo/docs/attachments/FPversion0p2/PaperSlicer/app.py", line 209, in export_svg
    section = self.mesh.section(
              ^^^^^^^^^^^^^^^^^^
  File "/Users/ger/Downloads/Fab_Academy/repo/docs/attachments/FPversion0p2/PaperSlicer/venv/lib/python3.12/site-packages/trimesh/base.py", line 2348, in section
    path = lines_to_path(lines)
           ^^^^^^^^^^^^^^^^^^^^
  File "/Users/ger/Downloads/Fab_Academy/repo/docs/attachments/FPversion0p2/PaperSlicer/venv/lib/python3.12/site-packages/trimesh/path/exchange/misc.py", line 79, in lines_to_path
    return edges_to_path(edges=inverse.reshape((-1, 2)), vertices=lines[unique])
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/ger/Downloads/Fab_Academy/repo/docs/attachments/FPversion0p2/PaperSlicer/venv/lib/python3.12/site-packages/trimesh/path/exchange/misc.py", line 212, in edges_to_path
    dfs = graph.traversals(edges, mode="dfs")
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/ger/Downloads/Fab_Academy/repo/docs/attachments/FPversion0p2/PaperSlicer/venv/lib/python3.12/site-packages/trimesh/graph.py", line 670, in traversals
    func = csgraph.depth_first_order
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/ger/Downloads/Fab_Academy/repo/docs/attachments/FPversion0p2/PaperSlicer/venv/lib/python3.12/site-packages/trimesh/exceptions.py", line 35, in __getattribute__
    raise exc_type(*exc_args)
ModuleNotFoundError: No module named 'scipy'

---

Add scipy.

requirements.txt

numpy
scipy
trimesh
shapely
ezdxf
svgwrite
tkinterdnd2

Install:

source venv/bin/activate
pip3 install scipy

Or rebuild:

rm -rf venv
./install.sh

trimesh.section() internally requires scipy graph traversal for contour extraction. Without scipy, slicing fails.

---

do I need it? can you make app.py without? show script

---

Yes, you can avoid scipy.

Do not use:

mesh.section()

Use direct triangle-plane intersection instead.

Replace your entire export_svg() with this:

def export_svg(self):

    if self.mesh is None:
        return

    os.makedirs("output", exist_ok=True)

    material_thickness = MATERIALS[
        self.material_var.get()
    ]

    vertices = self.mesh.vertices
    faces = self.mesh.faces

    zmin = vertices[:, 2].min()
    zmax = vertices[:, 2].max()

    layers = np.arange(
        zmin,
        zmax,
        material_thickness
    )

    dwg = svgwrite.Drawing(
        "output/slices.svg",
        profile="tiny"
    )

    spacing = 120
    x_offset = 0

    for z in layers:

        segments = []

        for face in faces:

            tri = vertices[face]

            points = []

            for i in range(3):

                p1 = tri[i]
                p2 = tri[(i + 1) % 3]

                z1 = p1[2]
                z2 = p2[2]

                intersects = (
                    (z1 <= z and z2 >= z) or
                    (z2 <= z and z1 >= z)
                )

                if not intersects:
                    continue

                dz = z2 - z1

                if abs(dz) < 1e-8:
                    continue

                t = (z - z1) / dz

                if 0 <= t <= 1:

                    p = p1 + t * (p2 - p1)

                    points.append(p)

            if len(points) == 2:

                segments.append([
                    (points[0][0], points[0][1]),
                    (points[1][0], points[1][1])
                ])

        for seg in segments:

            p1 = (
                seg[0][0] + x_offset,
                seg[0][1]
            )

            p2 = (
                seg[1][0] + x_offset,
                seg[1][1]
            )

            dwg.add(
                dwg.line(
                    start=p1,
                    end=p2,
                    stroke="black",
                    stroke_width=0.1
                )
            )

        x_offset += spacing

    dwg.save()

    print("Saved output/slices.svg")

Now you can remove scipy completely.

Final requirements.txt

numpy
trimesh
shapely
ezdxf
svgwrite
tkinterdnd2

This version:

no scipy
no matplotlib
no pillow
no pyglet
no OpenGL
minimal dependencies
pure triangle slicing
much easier packaging on macOS app bundles