From def87a59c0a774f798e1c1968089f255029917ef Mon Sep 17 00:00:00 2001
From: "zhou.xu" <zhou.xu@bambulab.com>
Date: Mon, 24 Apr 2023 17:01:00 +0800
Subject: [PATCH] FIX:The mirrored patch normal vector needs to be reversed

Change-Id: I3a67322eb59355ed91d1af390eb34f7f3d378198
(cherry picked from commit 3187f2b7944ddd2b9b6dc621da07dac6d4b3b31f)
---
 resources/shaders/mm_gouraud.fs              | 27 +++++++++-----------
 src/slic3r/GUI/Gizmos/GLGizmoFdmSupports.cpp |  2 +-
 2 files changed, 13 insertions(+), 16 deletions(-)

diff --git a/resources/shaders/mm_gouraud.fs b/resources/shaders/mm_gouraud.fs
index 86dc503a4d..4a74d75b56 100644
--- a/resources/shaders/mm_gouraud.fs
+++ b/resources/shaders/mm_gouraud.fs
@@ -44,27 +44,24 @@ void main()
     float alpha = uniform_color.a;
 
     vec3 triangle_normal = normalize(cross(dFdx(model_pos.xyz), dFdy(model_pos.xyz)));
-#ifdef FLIP_TRIANGLE_NORMALS
-    triangle_normal = -triangle_normal;
-#endif
-
+    if (volume_mirrored)
+    {
+        triangle_normal = -triangle_normal;
+    }
     vec3 transformed_normal = normalize(slope.volume_world_normal_matrix * triangle_normal);
+     
     if (slope.actived) {
-         if(world_pos.z<0.1&&world_pos.z>-0.1)
+        if(world_pos.z<0.1&&world_pos.z>-0.1)
          {
-                color = LightBlue;
-                alpha = 1.0;
+              color = LightBlue;
+              alpha = 1.0;
          }
          else if( transformed_normal.z < slope.normal_z - EPSILON)
-         {
-                color = color * 0.5 + LightRed * 0.5;
-                alpha = 1.0;
-         }
+        {
+            color = color * 0.5 + LightRed * 0.5;
+            alpha = 1.0;
+        }
     }
-
-    if (volume_mirrored)
-        triangle_normal = -triangle_normal;
-
     // First transform the normal into camera space and normalize the result.
     vec3 eye_normal = normalize(gl_NormalMatrix * triangle_normal);
 
diff --git a/src/slic3r/GUI/Gizmos/GLGizmoFdmSupports.cpp b/src/slic3r/GUI/Gizmos/GLGizmoFdmSupports.cpp
index b57ca0a9f8..c095c0915e 100644
--- a/src/slic3r/GUI/Gizmos/GLGizmoFdmSupports.cpp
+++ b/src/slic3r/GUI/Gizmos/GLGizmoFdmSupports.cpp
@@ -186,7 +186,7 @@ void GLGizmoFdmSupports::render_triangles(const Selection& selection) const
         shader->set_uniform("volume_world_matrix", trafo_matrix);
         shader->set_uniform("volume_mirrored", is_left_handed);
         shader->set_uniform("slope.actived", m_parent.is_using_slope());
-        shader->set_uniform("slope.volume_world_normal_matrix", static_cast<Matrix3f>(trafo_matrix.matrix().block(0, 0, 3, 3).inverse().transpose().cast<float>()));
+        shader->set_uniform("slope.volume_world_normal_matrix", normal_matrix);
         shader->set_uniform("slope.normal_z", normal_z);
         m_triangle_selectors[mesh_id]->render(m_imgui);