Trade: a reworked MeshData class.

With API analogous to the (relatively) new AnimationData -- with one
buffer containing all index data and one buffer containing all vertex
data, both meant to be uploaded as-is to the GPU.

This will eventually replace MeshData2D and MeshData3D, backwards
compatibility and wiring up to other APIs will be done in follow-up
commits.

doc/snippets/MagnumTrade.cpp

@@ -30,19 +30,24 @@
 
 #include "Magnum/FileCallback.h"
 #include "Magnum/ImageView.h"
+#include "Magnum/Mesh.h"
 #include "Magnum/PixelFormat.h"
+#include "Magnum/MeshTools/Interleave.h"
 #include "Magnum/Animation/Player.h"
 #include "Magnum/MeshTools/Transform.h"
 #include "Magnum/Trade/AbstractImporter.h"
 #include "Magnum/Trade/AnimationData.h"
 #include "Magnum/Trade/ImageData.h"
+#include "Magnum/Trade/MeshData.h"
 #include "Magnum/Trade/MeshData2D.h"
 #include "Magnum/Trade/MeshData3D.h"
 #include "Magnum/Trade/ObjectData2D.h"
 #include "Magnum/Trade/ObjectData3D.h"
 #include "Magnum/Trade/PhongMaterialData.h"
 #ifdef MAGNUM_TARGET_GL
 #include "Magnum/GL/Texture.h"
+#include "Magnum/GL/Mesh.h"
+#include "Magnum/Shaders/Phong.h"
 #endif
 
 using namespace Magnum;
@@ -201,6 +206,65 @@ else
 }
 #endif
 
+#ifdef MAGNUM_TARGET_GL
+{
+Trade::MeshData data{MeshPrimitive::Points, 0};
+/* [MeshData-usage] */
+/* Check that we have at least positions and normals */
+GL::Mesh mesh{data.primitive()};
+if(!data.hasAttribute(Trade::MeshAttributeName::Positions) ||
+   !data.hasAttribute(Trade::MeshAttributeName::Normals))
+    Fatal{} << "Oh well";
+
+/* Interleave vertex data */
+GL::Buffer vertices;
+vertices.setData(MeshTools::interleave(data.positions3D(), data.normals()));
+mesh.addVertexBuffer(std::move(vertices), 0,
+    Shaders::Phong::Position{}, Shaders::Phong::Normal{});
+
+/* Set up an index buffer, if the mesh is indexed*/
+if(data.isIndexed()) {
+    GL::Buffer indices;
+    indices.setData(data.indices());
+    mesh.setIndexBuffer(std::move(indices), 0, MeshIndexType::UnsignedInt)
+        .setCount(data.indexCount());
+} else mesh.setCount(data.vertexCount());
+/* [MeshData-usage] */
+}
+
+{
+Trade::MeshData data{MeshPrimitive::Points, 0};
+GL::Mesh mesh{data.primitive()};
+/* [MeshData-usage-advanced] */
+/* Upload the original packed vertex data */
+GL::Buffer vertices;
+vertices.setData(data.vertexData());
+
+/* Set up the position attribute */
+Shaders::Phong::Position position;
+auto positionType = data.attributeType(Trade::MeshAttributeName::Positions);
+if(positionType == MeshAttributeType::Vector2)
+    position = {Shaders::Phong::Position::Components::Two};
+else if(positionType == MeshAttributeType::Vector3)
+    position = {Shaders::Phong::Position::Components::Three};
+else Fatal{} << "Huh?";
+mesh.addVertexBuffer(vertices,
+    data.attributeOffset(Trade::MeshAttributeName::Positions),
+    data.attributeStride(Trade::MeshAttributeName::Positions), position);
+
+// Set up other attributes ...
+
+/* Upload the original packed index data */
+if(data.isIndexed()) {
+    GL::Buffer indices;
+    indices.setData(data.indexData());
+    mesh.setIndexBuffer(std::move(indices), 0, data.indexType())
+        .setCount(data.indexCount());
+} else mesh.setCount(data.vertexCount());
+/* [MeshData-usage-advanced] */
+}
+#endif
+
 {
 Trade::MeshData2D& foo();
 Trade::MeshData2D& data = foo();

src/Magnum/Trade/CMakeLists.txt

@@ -41,6 +41,7 @@ set(MagnumTrade_GracefulAssert_SRCS
     AnimationData.cpp
     CameraData.cpp
     ImageData.cpp
+    MeshData.cpp
     ObjectData2D.cpp
     ObjectData3D.cpp
     PhongMaterialData.cpp)
@@ -53,6 +54,7 @@ set(MagnumTrade_HEADERS
     CameraData.h
     ImageData.h
     LightData.h
+    MeshData.h
     MeshData2D.h
     MeshData3D.h
     MeshObjectData2D.h