From 9a8f9be2e639d97848c41571fd5dcb36580cdb25 Mon Sep 17 00:00:00 2001
From: Michael Dawson-Haggerty <mikedh@kerfed.com>
Date: Fri, 10 May 2024 15:44:01 -0400
Subject: [PATCH] test and fix for #2224

---
 tests/test_paths.py           | 20 ++++++++++++++++++++
 trimesh/constants.py          |  8 ++++++--
 trimesh/path/exchange/misc.py |  3 ++-
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/tests/test_paths.py b/tests/test_paths.py
index 61c2a44dd..9aa8ff04b 100644
--- a/tests/test_paths.py
+++ b/tests/test_paths.py
@@ -298,6 +298,26 @@ def test_section(self):
             # should be a valid Path2D
             g.check_path2D(planar)
 
+    def test_multiplane(self):
+        # check to make sure we're applying `tol_path.merge_digits` for line segments
+        vertices = g.np.array(
+            [
+                [19.402250931139097, -14.88787016674277, 64.0],
+                [20.03318396099334, -14.02738654377374, 64.0],
+                [19.402250931139097, -14.88787016674277, 0.0],
+                [20.03318396099334, -14.02738654377374, 0.0],
+                [21, -16.5, 32],
+            ]
+        )
+        faces = g.np.array(
+            [[1, 3, 0], [0, 3, 2], [1, 0, 4], [0, 2, 4], [3, 1, 4], [2, 3, 4]]
+        )
+        z_layer_centers = g.np.array([3, 3.0283334255218506])
+        m = g.trimesh.Trimesh(vertices, faces)
+        r = m.section_multiplane([0, 0, 0], [0, 0, 1], z_layer_centers)
+        assert len(r) == 2
+        assert all(i.is_closed for i in r)
+
 
 if __name__ == "__main__":
     g.trimesh.util.attach_to_log()
diff --git a/trimesh/constants.py b/trimesh/constants.py
index 28d4cdcf1..3c79982f2 100644
--- a/trimesh/constants.py
+++ b/trimesh/constants.py
@@ -2,7 +2,7 @@
 
 import numpy as np
 
-from .util import log, now
+from .util import decimal_to_digits, log, now
 
 
 @dataclass
@@ -88,6 +88,7 @@ class TolerancePath:
 
     zero: float = 1e-12
     merge: float = 1e-5
+
     planar: float = 1e-5
     seg_frac: float = 0.125
     seg_angle: float = float(np.radians(50))
@@ -98,9 +99,12 @@ class TolerancePath:
     radius_min: float = 1e-4
     radius_max: float = 50.0
     tangent: float = float(np.radians(20))
-
     strict: bool = False
 
+    @property
+    def merge_digits(self) -> int:
+        return decimal_to_digits(self.merge)
+
 
 @dataclass
 class ResolutionPath:
diff --git a/trimesh/path/exchange/misc.py b/trimesh/path/exchange/misc.py
index e99d56429..2ae3423ed 100644
--- a/trimesh/path/exchange/misc.py
+++ b/trimesh/path/exchange/misc.py
@@ -1,6 +1,7 @@
 import numpy as np
 
 from ... import graph, grouping, util
+from ...constants import tol_path
 from ..entities import Arc, Line
 
 
@@ -62,7 +63,7 @@ def lines_to_path(lines):
         # convert lines to even number of (n, dimension) points
         lines = lines.reshape((-1, dimension))
         # merge duplicate vertices
-        unique, inverse = grouping.unique_rows(lines)
+        unique, inverse = grouping.unique_rows(lines, digits=tol_path.merge_digits)
         # use scipy edges_to_path to skip creating
         # a bajillion individual line entities which
         # will be super slow vs. fewer polyline entities