From 5737b3241f716b77f8b54f5868a80c0bb6ee189e Mon Sep 17 00:00:00 2001
From: wmayer <wmayer@users.sourceforge.net>
Date: Fri, 9 Nov 2018 13:42:38 +0100
Subject: [PATCH] Allow user to define a custom minimum deviation for the
 tessellation

---
 src/Mod/Part/Gui/DlgSettings3DViewPartImp.cpp | 4 ++++
 src/Mod/Part/Gui/ViewProviderExt.cpp          | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/src/Mod/Part/Gui/DlgSettings3DViewPartImp.cpp b/src/Mod/Part/Gui/DlgSettings3DViewPartImp.cpp
index a6cbcbe34d..f0348e9257 100644
--- a/src/Mod/Part/Gui/DlgSettings3DViewPartImp.cpp
+++ b/src/Mod/Part/Gui/DlgSettings3DViewPartImp.cpp
@@ -46,6 +46,10 @@ DlgSettings3DViewPart::DlgSettings3DViewPart(QWidget* parent)
   : PreferencePage(parent), ui(new Ui_DlgSettings3DViewPart), checkValue(false)
 {
     ui->setupUi(this);
+    ParameterGrp::handle hPart = App::GetApplication().GetParameterGroupByPath
+        ("User parameter:BaseApp/Preferences/Mod/Part");
+    double lowerLimit = hPart->GetFloat("MinimumDeviation", ui->maxDeviation->minimum());
+    ui->maxDeviation->setMinimum(lowerLimit);
 }
 
 /** 
diff --git a/src/Mod/Part/Gui/ViewProviderExt.cpp b/src/Mod/Part/Gui/ViewProviderExt.cpp
index c432092ef4..748e04534f 100644
--- a/src/Mod/Part/Gui/ViewProviderExt.cpp
+++ b/src/Mod/Part/Gui/ViewProviderExt.cpp
@@ -241,6 +241,12 @@ ViewProviderPartExt::ViewProviderPartExt()
         ("User parameter:BaseApp/Preferences/Mod/Part");
     NormalsFromUV = hPart->GetBool("NormalsFromUVNodes", NormalsFromUV);
 
+    // Let the user define a custom lower limit but a value less than
+    // OCCT's epsilon is not allowed
+    double lowerLimit = hPart->GetFloat("MinimumDeviation", tessRange.LowerBound);
+    lowerLimit = std::max(lowerLimit, Precision::Confusion());
+    tessRange.LowerBound = lowerLimit;
+
     App::Material mat;
     mat.ambientColor.set(0.2f,0.2f,0.2f);
     mat.diffuseColor.set(r,g,b);