From 5ddf9f9620417869ef5ca0325272ea4c8d8b0528 Mon Sep 17 00:00:00 2001
From: orlandini <francisco.orlandini@gmail.com>
Date: Tue, 5 Sep 2023 10:47:41 -0300
Subject: [PATCH] refactor(changeel): ChangeToArc3D refactor + using manvector

---
 SpecialMaps/tpzchangeel.cpp | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/SpecialMaps/tpzchangeel.cpp b/SpecialMaps/tpzchangeel.cpp
index e220a4f26..9aa3f7172 100644
--- a/SpecialMaps/tpzchangeel.cpp
+++ b/SpecialMaps/tpzchangeel.cpp
@@ -435,24 +435,25 @@ TPZGeoEl * TPZChangeEl::ChangeToArc3D(TPZGeoMesh *mesh, const int64_t ElemIndex,
 
     auto CreateMidNode = [](const TPZVec<REAL> &x1, const TPZVec<REAL> &x2,
                             const REAL r,
-                            const TPZVec<REAL> &xcenter){
-        TPZVec<REAL> x3(3,0);
-        const auto &xc = xcenter[0];
-        const auto &yc = xcenter[1];
-        const auto &zc = xcenter[2];
+                            const TPZVec<REAL> &xc){
+        TPZManVector<REAL,3> x3(3,0);
         
-        //first we get its distance from xc
-        x3[0] = (x1[0] + x2[0])/2 - xc;
-        x3[1] = (x1[1] + x2[1])/2 - yc;
-        x3[2] = (x1[2] + x2[2])/2 - zc;
+        //first we get the midpoint's direction (bissecting the arc)
+        //this wont work if the angle between the vectors is pi
+        REAL vecnorm{0};
+        for(int ix = 0; ix < 3; ix++){
+            const auto val  = (x1[ix] + x2[ix])/2 - xc[ix];
+            x3[ix] = val;
+            vecnorm += val*val;
+        }
 
         //norm of the vector
-        const auto vecnorm = sqrt(x3[0]*x3[0] + x3[1]*x3[1] + x3[2]*x3[2]);
+        vecnorm = sqrt(vecnorm);
 
         //mid-arc coordinates
-        x3[0] = xc + r * x3[0]/vecnorm;
-        x3[1] = yc + r * x3[1]/vecnorm;
-        x3[2] = zc + r * x3[2]/vecnorm;
+        for(int ix = 0; ix < 3; ix++){
+            x3[ix] = xc[ix] + r * x3[ix]/vecnorm;
+        }
         return x3;
     };