[WIP] Trade: Implement support for Weights & JointIndices in MeshData.

Signed-off-by: Squareys <squareys@googlemail.com>

src/Magnum/Trade/MeshData.cpp

@@ -777,6 +777,18 @@ Containers::Array<UnsignedInt> MeshData::objectIdsAsArray(const UnsignedInt id)
     return out;
 }
 
+Containers::Array<Vector4> MeshData::weightsAsArray(const UnsignedInt id) const {
+    Containers::Array<Vector4> out{_vertexCount};
+    weightsInto(out, id);
+    return out;
+}
+
+Containers::Array<Vector4us> MeshData::jointIndicesAsArray(const UnsignedInt id) const {
+    Containers::Array<Vector4us> out{_vertexCount};
+    jointIndicesInto(out, id);
+    return out;
+}
+
 Containers::Array<char> MeshData::releaseIndexData() {
     _indexCount = 0;
     Containers::Array<char> out = std::move(_indexData);

src/Magnum/Trade/MeshData.h

@@ -147,6 +147,24 @@ enum class MeshAttribute: UnsignedShort {
      */
     ObjectId,
 
+    /**
+     * Weights. Type is usually @ref VertexFormat::Vector4, but can be also
+     * @ref VertexFormat::Vector4h, @ref VertexFormat::Vector4bNormalized or
+     * @ref VertexFormat::Vector4sNormalized. Corresponds to
+     * @ref Shaders::Generic::Weights.
+     * @see @ref MeshData::weightsAsArray()
+     */
+    Weights,
+
+    /**
+     * JointIndices. Type is usually @ref VertexFormat::Vector4ui, but can be also
+     * @ref VertexFormat::Vector4i, @ref VertexFormat::Vector4s, @ref VertexFormat::Vector4us,
+     * @ref VertexFormat::Vector4ub or @ref VertexFormat::Vector4b. Corresponds to
+     * @ref Shaders::Generic::JointIndices.
+     * @see @ref MeshData::jointIndicesAsArray()
+     */
+    JointIndices,
+
     /**
      * This and all higher values are for importer-specific attributes. Can be
      * of any type. See documentation of a particular importer for details.
@@ -613,10 +631,11 @@ the @ref Primitives library.
 The simplest usage is through the convenience functions @ref positions2DAsArray(),
 @ref positions3DAsArray(), @ref tangentsAsArray(), @ref bitangentsAsArray(),
 @ref normalsAsArray(), @ref tangentsAsArray(), @ref textureCoordinates2DAsArray(),
-@ref colorsAsArray() and @ref objectIdsAsArray(). Each of these takes an index
-(as there can be multiple sets of texture coordinates, for example) and you're
-expected to check for attribute presence first with either @ref hasAttribute()
-or @ref attributeCount(MeshAttribute) const:
+@ref colorsAsArray(), @ref objectIdsAsArray(), @ref weightsAsArray() and
+@ref jointIndicesAsArray(). Each of these takes an index (as there can be multiple
+sets of texture coordinates, for example) and you're expected to check for
+attribute presence first with either @ref hasAttribute() or
+@ref attributeCount(MeshAttribute) const:
 
 @snippet MagnumTrade.cpp MeshData-usage
 
@@ -1717,6 +1736,54 @@ class MAGNUM_TRADE_EXPORT MeshData {
          */
         void objectIdsInto(Containers::StridedArrayView1D<UnsignedInt> destination, UnsignedInt id = 0) const;
 
+        /**
+         * @brief Weights as 4D float vectors
+         *
+         * Convenience alternative to @ref attribute(MeshAttribute, UnsignedInt) const
+         * with @ref MeshAttribute::Weights as the first argument. Converts
+         * the weights array from an arbitrary underlying type and returns it
+         * in a newly-allocated array. Expects that the vertex format is *not*
+         * implementation-specific, in that case you can only access the
+         * attribute via the typeless @ref attribute(MeshAttribute, UnsignedInt) const.
+         * @see @ref weightsInto(), @ref attributeFormat(),
+         *      @ref isVertexFormatImplementationSpecific()
+         */
+        Containers::Array<Vector4> weightsAsArray(UnsignedInt id = 0) const;
+
+        /**
+         * @brief Weights as 4D float vectors into a pre-allocated view
+         *
+         * Like @ref weightsAsArray(), but puts the result into
+         * @p destination instead of allocating a new array. Expects that
+         * @p destination is sized to contain exactly all data.
+         * @see @ref vertexCount()
+         */
+        void weightsInto(Containers::StridedArrayView1D<Vector4> destination, UnsignedInt id = 0) const;
+
+        /**
+         * @brief Weights as 4D unsigned short vectors
+         *
+         * Convenience alternative to @ref attribute(MeshAttribute, UnsignedInt) const
+         * with @ref MeshAttribute::JointIndices as the first argument. Converts
+         * the joint indices array from an arbitrary underlying type and returns it
+         * in a newly-allocated array. Expects that the vertex format is *not*
+         * implementation-specific, in that case you can only access the
+         * attribute via the typeless @ref attribute(MeshAttribute, UnsignedInt) const.
+         * @see @ref jointIndicesInto(), @ref attributeFormat(),
+         *      @ref isVertexFormatImplementationSpecific()
+         */
+        Containers::Array<Vector4us> jointIndicesAsArray(UnsignedInt id = 0) const;
+
+        /**
+         * @brief Weights as 4D unsigned short vectors into a pre-allocated view
+         *
+         * Like @ref jointIndicesAsArray(), but puts the result into
+         * @p destination instead of allocating a new array. Expects that
+         * @p destination is sized to contain exactly all data.
+         * @see @ref vertexCount()
+         */
+        void jointIndicesInto(Containers::StridedArrayView1D<Vector4us> destination, UnsignedInt id = 0) const;
+
         /**
          * @brief Release index data storage
          *