sceneconverter: add --passthrough-on-*-converter-failure.

When using the -P or -M options on a large scene, it can happen that
the conversion would fail for a small number of outliers. For example
there can be some line meshes which aren't supported by MeshOptimizer,
or there are 16-bit images not supported by a certain image conversion
plugin.

Failing the whole operation in that case may be too radical, especially
if the only alternative would be to write a Python script that deals
with the outliers in a custom way. The option simply makes the
processing step pass through the original data unchanged, which may be a
simple and good-enough solution in many of those cases.

src/Magnum/SceneTools/Test/CMakeLists.txt

@@ -106,6 +106,10 @@ if(CORRADE_TARGET_UNIX AND NOT CORRADE_PLUGINMANAGER_NO_DYNAMIC_PLUGIN_SUPPORT)
             SceneConverterTestFiles/broken-scene.gltf
             SceneConverterTestFiles/dxt1.dds
             SceneConverterTestFiles/empty.gltf
+            # Same as blue4x4.png, just named like this to have the file
+            # roundtrip on conversion
+            SceneConverterTestFiles/image-passthrough-on-failure.0.png
+            SceneConverterTestFiles/image-passthrough-on-failure.gltf
             SceneConverterTestFiles/image-dds.gltf
             SceneConverterTestFiles/images-2d.gltf
             SceneConverterTestFiles/images-2d-1x1.bin
@@ -125,6 +129,8 @@ if(CORRADE_TARGET_UNIX AND NOT CORRADE_PLUGINMANAGER_NO_DYNAMIC_PLUGIN_SUPPORT)
             SceneConverterTestFiles/materials-phong.mtl
             SceneConverterTestFiles/materials-phong.obj
             SceneConverterTestFiles/materials-separate-metalness-roughness.mtl
+            SceneConverterTestFiles/mesh-passthrough-on-failure.bin
+            SceneConverterTestFiles/mesh-passthrough-on-failure.gltf
             SceneConverterTestFiles/point.obj
             SceneConverterTestFiles/quad-duplicates-fuzzy.obj
             SceneConverterTestFiles/quad-duplicates.obj

src/Magnum/SceneTools/Test/SceneConverterTest.cpp

@@ -594,6 +594,20 @@ const struct {
         "    65536 -> 65536 shaded pixels\n"
         "    65536 -> 65536 covered pixels\n"
         "    overdraw 1 -> 1\n"},
+    {"mesh converter, passthrough on failure", {InPlaceInit, {
+            "-M", "MeshOptimizerSceneConverter",
+            "--passthrough-on-mesh-converter-failure",
+            /* Removing the generator identifier for a roundtrip */
+            "-c", "generator=",
+            Utility::Path::join(SCENETOOLS_TEST_DIR, "SceneConverterTestFiles/mesh-passthrough-on-failure.gltf"),
+            Utility::Path::join(SCENETOOLS_TEST_OUTPUT_DIR, "SceneConverterTestFiles/mesh-passthrough-on-failure.gltf")
+        }},
+        "GltfImporter", nullptr, "GltfSceneConverter",
+        {}, "MeshOptimizerSceneConverter",
+        /* The output is exactly the same as the input */
+        "mesh-passthrough-on-failure.gltf", "mesh-passthrough-on-failure.bin",
+        "Trade::MeshOptimizerSceneConverter::convert(): expected an indexed mesh\n"
+        "Cannot process mesh 0 with MeshOptimizerSceneConverter, passing the original through\n"},
     {"2D image converter, two images", {InPlaceInit, {
             "-P", "StbResizeImageConverter", "-p", "size=\"1 1\"",
             /* Removing the generator identifier for a smaller file, bundling
@@ -673,6 +687,21 @@ const struct {
         "Processing 3D image 1 with StbResizeImageConverter...\n"
         "Trade::AbstractSceneConverter::addImporterContents(): adding texture 0 out of 2\n"
         "Trade::AbstractSceneConverter::addImporterContents(): adding texture 1 out of 2\n"},
+    {"2D image converter, passthrough on failure", {InPlaceInit, {
+            /* Size explicitly not set to trigger a failure */
+            "-P", "StbResizeImageConverter",
+            "--passthrough-on-image-converter-failure",
+            /* Removing the generator identifier for a roundtrip */
+            "-c", "generator=",
+            Utility::Path::join(SCENETOOLS_TEST_DIR, "SceneConverterTestFiles/image-passthrough-on-failure.gltf"),
+            Utility::Path::join(SCENETOOLS_TEST_OUTPUT_DIR, "SceneConverterTestFiles/image-passthrough-on-failure.gltf")
+        }},
+        "GltfImporter", "PngImporter", "GltfSceneConverter",
+        {"StbResizeImageConverter", "PngImageConverter"}, nullptr,
+        /* The output is exactly the same as the input */
+        "image-passthrough-on-failure.gltf", "image-passthrough-on-failure.0.png",
+        "Trade::StbResizeImageConverter::convert(): output size was not specified\n"
+        "Cannot process 2D image 0 with StbResizeImageConverter, passing the original through\n"},
     {"Phong to PBR", {InPlaceInit, {
             "-I", "UfbxImporter", "-C", "GltfSceneConverter", "--phong-to-pbr",
             /* We need the file as minimal as possible, so no index buffer.

src/Magnum/SceneTools/Test/SceneConverterTestFiles/image-passthrough-on-failure.gltf

@@ -0,0 +1,10 @@
+{
+  "asset": {
+    "version": "2.0"
+  },
+  "images": [
+    {
+      "uri": "image-passthrough-on-failure.0.png"
+    }
+  ]
+}

src/Magnum/SceneTools/Test/SceneConverterTestFiles/mesh-passthrough-on-failure.bin.in

@@ -0,0 +1,16 @@
+type = "3f3f3f 3f3f3f"
+input = [
+    # 2 3--5
+    # |\ \ |
+    # | \ \|
+    # 0--1 4
+    -1, -1, 0,
+     1, -1, 0,
+    -1,  1, 0,
+
+    -1,  1, 0,
+     1, -1, 0,
+     1,  1, 0,
+]
+
+# kate: hl python

src/Magnum/SceneTools/Test/SceneConverterTestFiles/mesh-passthrough-on-failure.gltf

@@ -0,0 +1,37 @@
+{
+  "asset": {
+    "version": "2.0"
+  },
+  "buffers": [
+    {
+      "uri": "mesh-passthrough-on-failure.bin",
+      "byteLength": 72
+    }
+  ],
+  "bufferViews": [
+    {
+      "buffer": 0,
+      "byteOffset": 0,
+      "byteLength": 72
+    }
+  ],
+  "accessors": [
+    {
+      "bufferView": 0,
+      "componentType": 5126,
+      "count": 6,
+      "type": "VEC3"
+    }
+  ],
+  "meshes": [
+    {
+      "primitives": [
+        {
+          "attributes": {
+            "POSITION": 0
+          }
+        }
+      ]
+    }
+  ]
+}

src/Magnum/SceneTools/sceneconverter.cpp

@@ -186,6 +186,8 @@ magnum-sceneconverter [-h|--help] [-I|--importer PLUGIN]
     [-c|--converter-options key=val,key2=val2,…]...
     [-p|--image-converter-options key=val,key2=val2,…]...
     [-m|--mesh-converter-options key=val,key2=val2,…]...
+    [--passthrough-on-image-converter-failure]
+    [--passthrough-on-mesh-converter-failure]
     [--mesh ID] [--mesh-level INDEX] [--concatenate-meshes] [--info-importer]
     [--info-converter] [--info-image-converter] [--info-animations]
     [--info-images] [--info-lights] [--info-cameras] [--info-materials]
@@ -228,6 +230,10 @@ Arguments:
     options to pass to image converter(s)
 -   `-m`, `--mesh-converter-options key=val,key2=val2,…` --- configuration
     options to pass to mesh converter(s)
+-   `--passthrough-on-image-converter-failure` --- pass original data through
+    if `--image-converter` fails
+-   `--passthrough-on-mesh-converter-failure` --- pass original data through
+    if `--mesh-converter` fails
 -   `--mesh ID` --- convert just a single mesh instead of the whole scene
 -   `--mesh-level LEVEL` --- level to select for single-mesh conversion
 -   `--concatenate-meshes` --- flatten mesh hierarchy and concatenate them all
@@ -335,6 +341,8 @@ bool isDataInfoRequested(const Utility::Arguments& args) {
 }
 
 template<UnsignedInt dimensions> bool runImageConverters(PluginManager::Manager<Trade::AbstractImageConverter>& imageConverterManager, const Utility::Arguments& args, const UnsignedInt i, Containers::Optional<Trade::ImageData<dimensions>>& image) {
+    const bool passthroughOnConversionFailure = args.isSet("passthrough-on-image-converter-failure");
+
     for(std::size_t j = 0, imageConverterCount = args.arrayValueCount("image-converter"); j != imageConverterCount; ++j) {
         const Containers::StringView imageConverterName = args.arrayValue<Containers::StringView>("image-converter", j);
         if(args.isSet("verbose")) {
@@ -381,7 +389,11 @@ template<UnsignedInt dimensions> bool runImageConverters(PluginManager::Manager<
         /** @todo handle image levels here, once GltfSceneConverter is capable
             of converting them (which needs AbstractImageConverter to be
             reworked around ImageData) */
-        if(!(image = imageConverter->convert(*image))) {
+        if(Containers::Optional<Trade::ImageData<dimensions>> converted = imageConverter->convert(*image)) {
+            image = std::move(converted);
+        } else if(passthroughOnConversionFailure) {
+            Warning{} << "Cannot process" << dimensions << Debug::nospace << "D image" << i << "with" << imageConverterName << Debug::nospace << ", passing the original through";
+        } else {
             Error{} << "Cannot process" << dimensions << Debug::nospace << "D image" << i << "with" << imageConverterName;
             return false;
         }
@@ -412,6 +424,8 @@ int main(int argc, char** argv) {
         .addArrayOption('c', "converter-options").setHelp("converter-options", "configuration options to pass to the converter(s)", "key=val,key2=val2,…")
         .addArrayOption('p', "image-converter-options").setHelp("image-converter-options", "configuration options to pass to the image converter(s)", "key=val,key2=val2,…")
         .addArrayOption('m', "mesh-converter-options").setHelp("mesh-converter-options", "configuration options to pass to the mesh converter(s)", "key=val,key2=val2,…")
+        .addBooleanOption("passthrough-on-image-converter-failure").setHelp("passthrough-on-image-converter-failure", "pass original data through if --image-converter fails")
+        .addBooleanOption("passthrough-on-mesh-converter-failure").setHelp("passthrough-on-mesh-converter-failure", "pass original data through if --mesh-converter fails")
         .addOption("mesh").setHelp("mesh", "convert just a single mesh instead of the whole scene, ignored if --concatenate-meshes is specified", "ID")
         .addOption("mesh-level").setHelp("mesh-level", "level to select for single-mesh conversion", "index")
         .addBooleanOption("concatenate-meshes").setHelp("concatenate-meshes", "flatten mesh hierarchy and concatenate them all together")
@@ -879,6 +893,8 @@ well, the IDs reference attributes of the first mesh.)")
        args.value<Containers::StringView>("remove-duplicate-vertices-fuzzy") ||
        args.arrayValueCount("mesh-converter"))
     {
+        const bool passthroughOnConversionFailure = args.isSet("passthrough-on-mesh-converter-failure");
+
         arrayReserve(meshes, importer->meshCount());
 
         for(UnsignedInt i = 0; i != importer->meshCount(); ++i) {
@@ -954,7 +970,11 @@ well, the IDs reference attributes of the first mesh.)")
 
                 /** @todo handle mesh levels here, once any plugin is capable
                     of converting them */
-                if(!(mesh = meshConverter->convert(*mesh))) {
+                if(Containers::Optional<Trade::MeshData> converted = meshConverter->convert(*mesh)) {
+                    mesh = std::move(converted);
+                } else if(passthroughOnConversionFailure) {
+                    Warning{} << "Cannot process mesh" << i << "with" << meshConverterName << Debug::nospace << ", passing the original through";
+                } else {
                     Error{} << "Cannot process mesh" << i << "with" << meshConverterName;
                     return 1;
                 }