From e2fd46f82cc9692211c3a0b61758ef2939273a9c Mon Sep 17 00:00:00 2001
From: Kris Austin <kris.austin@gmail.com>
Date: Fri, 7 Aug 2026 11:22:26 -0500
Subject: [PATCH] fix: default-initialize WallToolPathsParams fields (#15138)

min_length_factor and is_top_or_bottom_layer had no default initializers, and the FillConcentric/FillConcentricInternal callers never set them, so WallToolPaths::removeSmallLines() thresholded on stack garbage. Which short extrusion lines it dropped then depended on memory layout, so concentric solid-infill output was nondeterministic between runs and across machines. Give every member a default, matching the adjacent FillParams. The perimeter path was already fine because it builds the struct via make_paths_params().
---
 src/libslic3r/Arachne/WallToolPaths.hpp | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/libslic3r/Arachne/WallToolPaths.hpp b/src/libslic3r/Arachne/WallToolPaths.hpp
index dde3dc785f..d7120a088c 100644
--- a/src/libslic3r/Arachne/WallToolPaths.hpp
+++ b/src/libslic3r/Arachne/WallToolPaths.hpp
@@ -23,14 +23,14 @@ inline coord_t    meshfix_maximum_extrusion_area_deviation() { return scaled<coo
 class WallToolPathsParams
 {
 public:
-    float   min_bead_width;
-    float   min_feature_size;
-    float   min_length_factor;
-    float   wall_transition_length;
-    float   wall_transition_angle;
-    float   wall_transition_filter_deviation;
-    int     wall_distribution_count;
-    bool    is_top_or_bottom_layer;
+    float   min_bead_width                   = 0.f;
+    float   min_feature_size                 = 0.f;
+    float   min_length_factor                = 0.5f;
+    float   wall_transition_length           = 0.f;
+    float   wall_transition_angle            = 10.f;
+    float   wall_transition_filter_deviation = 0.f;
+    int     wall_distribution_count          = 1;
+    bool    is_top_or_bottom_layer           = false;
 
     coord_t wall_maximum_resolution = meshfix_maximum_resolution();
     coord_t wall_maximum_deviation  = meshfix_maximum_deviation();