Primitives: added a wireframe icosphere.

doc/changelog.dox

@@ -210,6 +210,7 @@ See also:
     @ref Primitives::coneSolid(), @ref Primitives::cylinderSolid(),
     @ref Primitives::grid3DSolid(), @ref Primitives::planeSolid() and
     @ref Primitives::uvSphereSolid() can now have tangents as well
+-   Added @ref Primitives::icosphereWireframe()
 
 @subsubsection changelog-latest-new-scenegraph SceneGraph library
 

doc/generated/primitives.cpp

@@ -108,6 +108,7 @@ struct PrimitiveVisualizer: Platform::WindowlessApplication {
     std::pair<Trade::MeshData, std::string> cubeWireframe();
     std::pair<Trade::MeshData, std::string> cylinderWireframe();
     std::pair<Trade::MeshData, std::string> grid3DWireframe();
+    std::pair<Trade::MeshData, std::string> icosphereWireframe();
     std::pair<Trade::MeshData, std::string> line3D();
     std::pair<Trade::MeshData, std::string> planeWireframe();
     std::pair<Trade::MeshData, std::string> uvSphereWireframe();
@@ -257,6 +258,7 @@ int PrimitiveVisualizer::exec() {
                        &PrimitiveVisualizer::cubeWireframe,
                        &PrimitiveVisualizer::cylinderWireframe,
                        &PrimitiveVisualizer::grid3DWireframe,
+                       &PrimitiveVisualizer::icosphereWireframe,
                        &PrimitiveVisualizer::line3D,
                        &PrimitiveVisualizer::planeWireframe,
                        &PrimitiveVisualizer::uvSphereWireframe})
@@ -497,6 +499,10 @@ std::pair<Trade::MeshData, std::string> PrimitiveVisualizer::grid3DWireframe() {
     return {Primitives::grid3DWireframe({5, 3}), "grid3dwireframe.png"};
 }
 
+std::pair<Trade::MeshData, std::string> PrimitiveVisualizer::icosphereWireframe() {
+    return {Primitives::icosphereWireframe(), "icospherewireframe.png"};
+}
+
 std::pair<Trade::MeshData, std::string> PrimitiveVisualizer::line3D() {
     Trade::MeshData line = Primitives::line3D();
     MeshTools::transformPointsInPlace(Matrix4::translation(Vector3::xAxis(-1.0f))*Matrix4::scaling(Vector3::xScale(2.0f)),

src/Magnum/Primitives/Icosphere.cpp

@@ -42,16 +42,19 @@ constexpr UnsignedInt Indices[]{
     3, 4, 5,
     4, 3, 8,
     6, 5, 11,
+
     5, 6, 10,
     9, 10, 2,
     10, 9, 3,
     7, 8, 9,
     8, 7, 0,
+
     11, 0, 1,
     0, 11, 4,
     6, 2, 10,
     1, 6, 11,
     3, 5, 10,
+
     5, 4, 11,
     2, 7, 9,
     7, 1, 0,
@@ -59,26 +62,30 @@ constexpr UnsignedInt Indices[]{
     4, 8, 0
 };
 
-constexpr Vector3 Positions[]{
-    {0.0f, -0.525731f, 0.850651f},
-    {0.850651f, 0.0f, 0.525731f},
-    {0.850651f, 0.0f, -0.525731f},
-    {-0.850651f, 0.0f, -0.525731f},
-    {-0.850651f, 0.0f, 0.525731f},
-    {-0.525731f, 0.850651f, 0.0f},
-    {0.525731f, 0.850651f, 0.0f},
-    {0.525731f, -0.850651f, 0.0f},
-    {-0.525731f, -0.850651f, 0.0f},
-    {0.0f, -0.525731f, -0.850651f},
-    {0.0f, 0.525731f, -0.850651f},
-    {0.0f, 0.525731f, 0.850651f}
+/* Can't be just an array of Vector3 because MSVC 2015 is special. See
+   Crosshair.cpp for details. */
+constexpr struct VertexSolidStrip {
+    Vector3 position;
+} Vertices[]{
+    {{0.0f, -0.525731f, 0.850651f}},
+    {{0.850651f, 0.0f, 0.525731f}},
+    {{0.850651f, 0.0f, -0.525731f}},
+    {{-0.850651f, 0.0f, -0.525731f}},
+    {{-0.850651f, 0.0f, 0.525731f}},
+    {{-0.525731f, 0.850651f, 0.0f}},
+    {{0.525731f, 0.850651f, 0.0f}},
+    {{0.525731f, -0.850651f, 0.0f}},
+    {{-0.525731f, -0.850651f, 0.0f}},
+    {{0.0f, -0.525731f, -0.850651f}},
+    {{0.0f, 0.525731f, -0.850651f}},
+    {{0.0f, 0.525731f, 0.850651f}}
 };
 
 }
 
 Trade::MeshData icosphereSolid(const UnsignedInt subdivisions) {
     const std::size_t indexCount = Containers::arraySize(Indices)*(1 << subdivisions*2);
-    const std::size_t vertexCount = Containers::arraySize(Positions) + ((indexCount - Containers::arraySize(Indices))/3);
+    const std::size_t vertexCount = Containers::arraySize(Vertices) + ((indexCount - Containers::arraySize(Indices))/3);
 
     Containers::Array<char> indexData{indexCount*sizeof(UnsignedInt)};
     auto indices = Containers::arrayCast<UnsignedInt>(indexData);
@@ -96,12 +103,12 @@ Trade::MeshData icosphereSolid(const UnsignedInt subdivisions) {
     {
         auto vertices = Containers::arrayCast<Vertex>(vertexData);
         Containers::StridedArrayView1D<Vector3> positions{vertices, &vertices[0].position, vertices.size(), sizeof(Vertex)};
-        for(std::size_t i = 0; i != Containers::arraySize(Positions); ++i)
-            positions[i] = Positions[i];
+        for(std::size_t i = 0; i != Containers::arraySize(Vertices); ++i)
+            positions[i] = Vertices[i].position;
 
         for(std::size_t i = 0; i != subdivisions; ++i) {
             const std::size_t iterationIndexCount = Containers::arraySize(Indices)*(1 << (i + 1)*2);
-            const std::size_t iterationVertexCount = Containers::arraySize(Positions) + ((iterationIndexCount - Containers::arraySize(Indices))/3);
+            const std::size_t iterationVertexCount = Containers::arraySize(Vertices) + ((iterationIndexCount - Containers::arraySize(Indices))/3);
             MeshTools::subdivideInPlace(indices.prefix(iterationIndexCount), positions.prefix(iterationVertexCount), [](const Vector3& a, const Vector3& b) {
                 return (a+b).normalized();
             });
@@ -125,4 +132,39 @@ Trade::MeshData icosphereSolid(const UnsignedInt subdivisions) {
          Trade::MeshAttributeData{Trade::MeshAttribute::Normal, normals}}};
 }
 
+namespace {
+
+/* Taking the above, converting each triangle to three lines and leaving out
+   the duplicates. Because each edge is shared by two triangles and there was
+   20 triangles to begin with, there's 30 edges. */
+constexpr UnsignedInt IndicesWireframe[]{
+    1, 2, 2, 6, 6, 1,
+    1, 7, 7, 2,
+    3, 4, 4, 5, 5, 3,
+    3, 8, 8, 4,
+    6, 5, 5, 11, 11, 6,
+
+    6, 10, 10, 5,
+    9, 10, 10, 2, 2, 9,
+    9, 3, 3, 10,
+    7, 8, 8, 9, 9, 7,
+    7, 0, 0, 8,
+
+    11, 0, 0, 1, 1, 11,
+    11, 4, 4, 0
+};
+constexpr Trade::MeshAttributeData AttributesWireframe[]{
+    Trade::MeshAttributeData{Trade::MeshAttribute::Position,
+        Containers::stridedArrayView(Vertices, &Vertices[0].position,
+            Containers::arraySize(Vertices), sizeof(Vector3))}
+};
+
+}
+
+Trade::MeshData icosphereWireframe() {
+    return Trade::MeshData{MeshPrimitive::Lines,
+        {}, IndicesWireframe, Trade::MeshIndexData{IndicesWireframe},
+        {}, Vertices, Trade::meshAttributeDataNonOwningArray(AttributesWireframe)};
+}
+
 }}

src/Magnum/Primitives/Icosphere.h

@@ -47,14 +47,29 @@ normals.
 
 The @p subdivisions parameter describes how many times is each icosphere
 triangle subdivided, recursively. Specifying @cpp 0 @ce will result in an
-icosphere with 20 faces, saying @cpp 1 @ce will result in an icosphere with 80
-faces (each triangle subdivided into four smaller), saying @cpp 2 @ce will
-result in 320 faces and so on. In particular, this is different from the
-`subdivisions` parameter in @ref grid3DSolid() or @ref grid3DWireframe().
+icosphere with 12 vertices and 20 faces, saying @cpp 1 @ce will result in an
+icosphere with 80 faces (each triangle subdivided into four smaller), saying
+@cpp 2 @ce will result in 320 faces and so on. In particular, this is different
+from the `subdivisions` parameter in @ref grid3DSolid() or @ref grid3DWireframe().
 @see @ref uvSphereSolid(), @ref uvSphereWireframe()
 */
 MAGNUM_PRIMITIVES_EXPORT Trade::MeshData icosphereSolid(UnsignedInt subdivisions);
 
+/**
+@brief Wireframe 3D icosphere
+@m_since_latest
+
+Sphere of radius @cpp 1.0f @ce with 12 vertices and 30 edges, centered at
+origin. @ref MeshPrimitive::Lines with @ref MeshIndexType::UnsignedShort
+indices and @ref VertexFormat::Vector3 positions. The returned instance
+references data stored in constant memory.
+
+@image html primitives-icospherewireframe.png width=256px
+
+@see @ref icosphereWireframe()
+*/
+MAGNUM_PRIMITIVES_EXPORT Trade::MeshData icosphereWireframe();
+
 }}
 
 #endif

src/Magnum/Primitives/Test/IcosphereTest.cpp

@@ -38,12 +38,16 @@ struct IcosphereTest: TestSuite::Tester {
     void count0();
     void data1();
     void count2();
+
+    void wireframe();
 };
 
 IcosphereTest::IcosphereTest() {
     addTests({&IcosphereTest::count0,
               &IcosphereTest::data1,
-              &IcosphereTest::count2});
+              &IcosphereTest::count2,
+
+              &IcosphereTest::wireframe});
 }
 
 void IcosphereTest::count0() {
@@ -146,6 +150,16 @@ void IcosphereTest::count2() {
     CORRADE_COMPARE(icosphere.attributeCount(), 2);
 }
 
+void IcosphereTest::wireframe() {
+    Trade::MeshData icosphere = Primitives::icosphereWireframe();
+
+    CORRADE_COMPARE(icosphere.primitive(), MeshPrimitive::Lines);
+    CORRADE_VERIFY(icosphere.isIndexed());
+    CORRADE_COMPARE(icosphere.indexCount(), 60);
+    CORRADE_COMPARE(icosphere.vertexCount(), 12);
+    CORRADE_COMPARE(icosphere.attributeCount(), 1);
+}
+
 }}}}
 
 CORRADE_TEST_MAIN(Magnum::Primitives::Test::IcosphereTest)