MeshTools: added compressIndicesAs().

Much more convenient and "good enough" alternative to compressIndices().

src/Magnum/MeshTools/CMakeLists.txt

@@ -26,13 +26,13 @@
 # Files shared between main library and unit test library
 set(MagnumMeshTools_SRCS
     Compile.cpp
-    CompressIndices.cpp
     FullScreenTriangle.cpp
     Tipsify.cpp)
 
 # Files compiled with different flags for main library and unit test library
 set(MagnumMeshTools_GracefulAssert_SRCS
     CombineIndexedArrays.cpp
+    CompressIndices.cpp
     FlipNormals.cpp
     GenerateFlatNormals.cpp)
 

src/Magnum/MeshTools/CompressIndices.cpp

@@ -74,4 +74,21 @@ std::tuple<Containers::Array<char>, Mesh::IndexType, UnsignedInt, UnsignedInt> c
     return std::make_tuple(std::move(data), type, *minmax.first, *minmax.second);
 }
 
+template<class T> Containers::Array<T> compressIndicesAs(const std::vector<UnsignedInt>& indices) {
+    #if !defined(CORRADE_NO_ASSERT) || defined(CORRADE_GRACEFUL_ASSERT)
+    const auto max = std::max_element(indices.begin(), indices.end());
+    CORRADE_ASSERT(Math::log(256, *max) < sizeof(T), "MeshTools::compressIndicesAs(): type too small to represent value" << *max, {});
+    #endif
+
+    Containers::Array<T> buffer(indices.size());
+    for(std::size_t i = 0; i != indices.size(); ++i)
+        buffer[i] = indices[i];
+
+    return buffer;
+}
+
+template Containers::Array<UnsignedByte> compressIndicesAs(const std::vector<UnsignedInt>& indices);
+template Containers::Array<UnsignedShort> compressIndicesAs(const std::vector<UnsignedInt>& indices);
+template Containers::Array<UnsignedInt> compressIndicesAs(const std::vector<UnsignedInt>& indices);
+
 }}

src/Magnum/MeshTools/CompressIndices.h

@@ -62,10 +62,29 @@ Mesh mesh;
 mesh.setCount(indices.size())
     .setIndexBuffer(indexBuffer, 0, indexType, indexStart, indexEnd);
 @endcode
+
+@see @ref compressIndicesAs()
 @todo Extract IndexType out of Mesh class
 */
 std::tuple<Containers::Array<char>, Mesh::IndexType, UnsignedInt, UnsignedInt> MAGNUM_MESHTOOLS_EXPORT compressIndices(const std::vector<UnsignedInt>& indices);
 
+/**
+@brief Compress vertex indices as given type
+
+The type can be either @ref Magnum::UnsignedByte "UnsignedByte",
+@ref Magnum::UnsignedShort "UnsignedShort" or @ref Magnum::UnsignedInt "UnsignedInt".
+Values in the index array are expected to be representable with given type.
+
+Example usage:
+@code
+std::vector<UnsignedInt> indices;
+Containers::Array<UnsignedShort> indexData = MeshTools::compressIndicesAs<UnsignedShort>(indices);
+@endcode
+
+@see @ref compressIndices()
+*/
+template<class T> MAGNUM_MESHTOOLS_EXPORT Containers::Array<T> compressIndicesAs(const std::vector<UnsignedInt>& indices);
+
 }}
 
 #endif

src/Magnum/MeshTools/Test/CMakeLists.txt

@@ -24,7 +24,7 @@
 #
 
 corrade_add_test(MeshToolsCombineIndexedArraysTest CombineIndexedArraysTest.cpp LIBRARIES MagnumMeshToolsTestLib)
-corrade_add_test(MeshToolsCompressIndicesTest CompressIndicesTest.cpp LIBRARIES MagnumMeshTools)
+corrade_add_test(MeshToolsCompressIndicesTest CompressIndicesTest.cpp LIBRARIES MagnumMeshToolsTestLib)
 corrade_add_test(MeshToolsDuplicateTest DuplicateTest.cpp)
 corrade_add_test(MeshToolsFlipNormalsTest FlipNormalsTest.cpp LIBRARIES MagnumMeshToolsTestLib)
 corrade_add_test(MeshToolsGenerateFlatNormalsTest GenerateFlatNormalsTest.cpp LIBRARIES MagnumMeshToolsTestLib)

src/Magnum/MeshTools/Test/CompressIndicesTest.cpp

@@ -23,8 +23,10 @@
     DEALINGS IN THE SOFTWARE.
 */
 
+#include <sstream>
 #include <Corrade/Containers/Array.h>
 #include <Corrade/TestSuite/Tester.h>
+#include <Corrade/TestSuite/Compare/Container.h>
 #include <Corrade/Utility/Endianness.h>
 
 #include "Magnum/MeshTools/CompressIndices.h"
@@ -37,12 +39,16 @@ struct CompressIndicesTest: TestSuite::Tester {
     void compressChar();
     void compressShort();
     void compressInt();
+
+    void compressAsShort();
 };
 
 CompressIndicesTest::CompressIndicesTest() {
     addTests({&CompressIndicesTest::compressChar,
               &CompressIndicesTest::compressShort,
-              &CompressIndicesTest::compressInt});
+              &CompressIndicesTest::compressInt,
+
+              &CompressIndicesTest::compressAsShort});
 }
 
 void CompressIndicesTest::compressChar() {
@@ -108,6 +114,17 @@ void CompressIndicesTest::compressInt() {
     }
 }
 
+void CompressIndicesTest::compressAsShort() {
+    CORRADE_COMPARE_AS(MeshTools::compressIndicesAs<UnsignedShort>({123, 456}),
+        Containers::Array<UnsignedShort>::from(123, 456),
+        TestSuite::Compare::Container);
+
+    std::ostringstream out;
+    Error::setOutput(&out);
+    MeshTools::compressIndicesAs<UnsignedShort>({65536});
+    CORRADE_COMPARE(out.str(), "MeshTools::compressIndicesAs(): type too small to represent value 65536\n");
+}
+
 }}}
 
 CORRADE_TEST_MAIN(Magnum::MeshTools::Test::CompressIndicesTest)