From 29d4513694d9ff0d6d9915eaddfdf1c37b9f1a3d Mon Sep 17 00:00:00 2001
From: Kiss Lorand <50251547+kisslorand@users.noreply.github.com>
Date: Tue, 28 Jul 2026 23:46:14 +0300
Subject: [PATCH] Fix overlapping brims (#14991)

---
 src/libslic3r/Brim.cpp              | 22 ++++++++++++++--------
 tests/fff_print/test_skirt_brim.cpp | 18 ++++++++++++++++++
 2 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/src/libslic3r/Brim.cpp b/src/libslic3r/Brim.cpp
index 6473dc5c21..b22c9c323e 100644
--- a/src/libslic3r/Brim.cpp
+++ b/src/libslic3r/Brim.cpp
@@ -32,15 +32,13 @@ static void append_and_translate(ExPolygons &dst, const ExPolygons &src, const P
     for (; dst_idx < dst.size(); ++dst_idx)
         dst[dst_idx].translate(instance_shift);
 }
-// BBS: generate brim area by objs
-static void append_and_translate(ExPolygons& dst, const ExPolygons& src,
-    const PrintInstance& instance, size_t instance_idx, std::map<ObjectInstanceID, ExPolygons>& brimAreaMap) {
+// Orca: Translate the brim area into print coordinates and store it per instance.
+static void append_and_translate(const ExPolygons& src, const PrintInstance& instance,
+    size_t instance_idx, std::map<ObjectInstanceID, ExPolygons>& brimAreaMap) {
     ExPolygons srcShifted = src;
     Point instance_shift = instance.shift_without_plate_offset();
-    for (size_t src_idx = 0; src_idx < srcShifted.size(); ++src_idx)
-        srcShifted[src_idx].translate(instance_shift);
-    srcShifted = diff_ex(srcShifted, dst);
-    //expolygons_append(dst, temp2);
+    for (ExPolygon& expoly : srcShifted)
+        expoly.translate(instance_shift);
     expolygons_append(brimAreaMap[{ instance.print_object->id(), instance_idx }], std::move(srcShifted));
 }
 
@@ -572,7 +570,7 @@ static ExPolygons outer_inner_brim_area(const Print& print,
                 for (size_t instance_idx = 0; instance_idx < object->instances().size(); ++instance_idx) {
                     const PrintInstance& instance = object->instances()[instance_idx];
                     if (!brim_area_object.empty())
-                        append_and_translate(brim_area, brim_area_object, instance, instance_idx, brimAreaMap);
+                        append_and_translate(brim_area_object, instance, instance_idx, brimAreaMap);
                     append_and_translate(no_brim_area, no_brim_area_object, instance);
                     append_and_translate(holes, holes_object, instance);
                     append_and_translate(objectIslands, objectIsland, instance);
@@ -875,6 +873,14 @@ void make_brim(const Print& print, PrintTryCancel try_cancel, Polygons& islands_
     ExPolygons           islands_area_ex = outer_inner_brim_area(print,
         float(flow.scaled_spacing()), brimAreaMap, objPrintVec, printExtruders);
 
+    if (!print.config().combine_brims) {
+        ExPolygons claimed_area;
+        for (auto& [_, areas] : brimAreaMap) {
+            areas = diff_ex(areas, claimed_area);
+            expolygons_append(claimed_area, areas);
+        }
+    }
+
     // BBS: Find boundingbox of the first layer
     for (const ObjectID printObjID : print.print_object_ids()) {
         BoundingBox bbx;
diff --git a/tests/fff_print/test_skirt_brim.cpp b/tests/fff_print/test_skirt_brim.cpp
index d957a4c649..3f63d3de5f 100644
--- a/tests/fff_print/test_skirt_brim.cpp
+++ b/tests/fff_print/test_skirt_brim.cpp
@@ -153,6 +153,24 @@ TEST_CASE("Object brims are generated per instance", "[SkirtBrim]")
     }
 }
 
+TEST_CASE("Uncombined neighboring brims precede their respective objects", "[SkirtBrim]")
+{
+    Print print;
+    Model model;
+    place_two_cubes_apart(0, {
+        { "skirt_loops",   0 },
+        { "brim_type",     "outer_only" },
+        { "brim_width",    5 },
+        { "combine_brims", 0 },
+    }, print, model);
+    print.process();
+
+    REQUIRE(print.skirt_brim_groups().size() == 1);
+    REQUIRE(print.skirt_brim_groups().front().brims.size() == 2);
+    CHECK(role_sequence(gcode(print), { "brim", "perimeter" }) ==
+          std::vector<std::string>{ "brim", "perimeter", "brim", "perimeter" });
+}
+
 TEST_CASE("Combine brims merges neighboring object instances", "[SkirtBrim]")
 {
     Print print;