MeshTools: functions for flipping normals and face winding.

src/MeshTools/CMakeLists.txt

@@ -1,4 +1,5 @@
 set(MagnumMeshTools_SRCS
+    FlipNormals.cpp
     GenerateFlatNormals.cpp
     Tipsify.cpp
 )

src/MeshTools/FlipNormals.cpp

@@ -0,0 +1,38 @@
+/*
+    Copyright © 2010, 2011, 2012 Vladimír Vondruš <mosra@centrum.cz>
+
+    This file is part of Magnum.
+
+    Magnum is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License version 3
+    only, as published by the Free Software Foundation.
+
+    Magnum is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+    GNU Lesser General Public License version 3 for more details.
+*/
+
+#include "FlipNormals.h"
+
+using namespace std;
+using namespace Corrade::Utility;
+
+namespace Magnum { namespace MeshTools {
+
+void flipFaceWinding(vector<unsigned int>& indices) {
+    if(indices.size()%3 != 0) {
+        Error() << "MeshTools::flipNormals(): index count is not divisible by 3!";
+        return;
+    }
+
+    for(size_t i = 0; i != indices.size(); i += 3)
+        swap(indices[i+1], indices[i+2]);
+}
+
+void flipNormals(vector<Vector3>& normals) {
+    for(Vector3& normal: normals)
+        normal = -normal;
+}
+
+}}

src/MeshTools/FlipNormals.h

@@ -0,0 +1,61 @@
+#ifndef Magnum_MeshTools_FlipNormals_h
+#define Magnum_MeshTools_FlipNormals_h
+/*
+    Copyright © 2010, 2011, 2012 Vladimír Vondruš <mosra@centrum.cz>
+
+    This file is part of Magnum.
+
+    Magnum is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License version 3
+    only, as published by the Free Software Foundation.
+
+    Magnum is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+    GNU Lesser General Public License version 3 for more details.
+*/
+
+/** @file
+ * @brief Function Magnum::MeshTools::flipNormals()
+ */
+
+#include "Magnum.h"
+
+namespace Magnum { namespace MeshTools {
+
+/**
+@brief Flip face winding
+
+The same as flipNormals(std::vector<unsigned int>&, std::vector<Vector3>&),
+but flips only face winding.
+*/
+void flipFaceWinding(std::vector<unsigned int>& indices);
+
+/**
+@brief Flip mesh normals
+
+The same as flipNormals(std::vector<unsigned int>&, std::vector<Vector3>&),
+but flips only normals, not face winding.
+*/
+void flipNormals(std::vector<Vector3>& normals);
+
+/**
+@brief Flip mesh normals and face winding
+@param indices      Index array to operate on
+@param normals      Normal array to operate on
+
+Flips normal vectors and face winding in index array for face culling to work
+properly too. See also flipNormals(std::vector<Vector3>&) and
+flipFaceWinding(), which flip normals or face winding only.
+
+@attention The function requires the mesh to have triangle faces, thus index
+    count must be divisible by 3.
+*/
+inline void flipNormals(std::vector<unsigned int>& indices, std::vector<Vector3>& normals) {
+    flipFaceWinding(indices);
+    flipNormals(normals);
+}
+
+}}
+
+#endif

src/MeshTools/Test/CMakeLists.txt

@@ -1,6 +1,7 @@
 corrade_add_test(CleanTest CleanTest.h CleanTest.cpp ${CORRADE_UTILITY_LIBRARY})
 corrade_add_test(CombineIndexedArraysTest CombineIndexedArraysTest.h CombineIndexedArraysTest.cpp ${CORRADE_UTILITY_LIBRARY})
 corrade_add_test(CompressIndicesTest CompressIndicesTest.h CompressIndicesTest.cpp ${CORRADE_UTILITY_LIBRARY} ${MAGNUM_LIBRARY})
+corrade_add_test(FlipNormalsTest FlipNormalsTest.h FlipNormalsTest.cpp ${MAGNUM_MESHTOOLS_LIBRARY})
 corrade_add_test(GenerateFlatNormalsTest GenerateFlatNormalsTest.h GenerateFlatNormalsTest.cpp ${MAGNUM_MESHTOOLS_LIBRARY})
 corrade_add_test(InterleaveTest InterleaveTest.h InterleaveTest.cpp ${CORRADE_UTILITY_LIBRARY})
 corrade_add_test(SubdivideTest SubdivideTest.h SubdivideTest.cpp ${CORRADE_UTILITY_LIBRARY})

src/MeshTools/Test/FlipNormalsTest.cpp

@@ -0,0 +1,59 @@
+/*
+    Copyright © 2010, 2011, 2012 Vladimír Vondruš <mosra@centrum.cz>
+
+    This file is part of Magnum.
+
+    Magnum is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License version 3
+    only, as published by the Free Software Foundation.
+
+    Magnum is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+    GNU Lesser General Public License version 3 for more details.
+*/
+
+#include "FlipNormalsTest.h"
+
+#include <sstream>
+#include <QtTest/QTest>
+#include "MeshTools/FlipNormals.h"
+
+QTEST_APPLESS_MAIN(Magnum::MeshTools::Test::FlipNormalsTest)
+
+using namespace std;
+using namespace Corrade::Utility;
+
+namespace Magnum { namespace MeshTools { namespace Test {
+
+void FlipNormalsTest::wrongIndexCount() {
+    stringstream ss;
+    Error::setOutput(&ss);
+
+    vector<unsigned int> indices{0, 1};
+    MeshTools::flipFaceWinding(indices);
+
+    QVERIFY(ss.str() == "MeshTools::flipNormals(): index count is not divisible by 3!\n");
+}
+
+void FlipNormalsTest::flipFaceWinding() {
+    vector<unsigned int> indices{0, 1, 2,
+                                 3, 4, 5};
+    MeshTools::flipFaceWinding(indices);
+
+    QVERIFY((indices == vector<unsigned int>{0, 2, 1,
+                                             3, 5, 4}));
+}
+
+void FlipNormalsTest::flipNormals() {
+    vector<Vector3> normals{Vector3::xAxis(),
+                            Vector3::yAxis(),
+                            Vector3::zAxis()};
+    MeshTools::flipNormals(normals);
+
+    QVERIFY((normals == vector<Vector3>{-Vector3::xAxis(),
+                                        -Vector3::yAxis(),
+                                        -Vector3::zAxis()}));
+}
+
+}}}

src/MeshTools/Test/FlipNormalsTest.h

@@ -0,0 +1,33 @@
+#ifndef Magnum_MeshTools_Test_FlipNormalsTest_h
+#define Magnum_MeshTools_Test_FlipNormalsTest_h
+/*
+    Copyright © 2010, 2011, 2012 Vladimír Vondruš <mosra@centrum.cz>
+
+    This file is part of Magnum.
+
+    Magnum is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License version 3
+    only, as published by the Free Software Foundation.
+
+    Magnum is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+    GNU Lesser General Public License version 3 for more details.
+*/
+
+#include <QtCore/QObject>
+
+namespace Magnum { namespace MeshTools { namespace Test {
+
+class FlipNormalsTest: public QObject {
+    Q_OBJECT
+
+    private slots:
+        void wrongIndexCount();
+        void flipFaceWinding();
+        void flipNormals();
+};
+
+}}}
+
+#endif