doc: now that plugins "just work", we can be honest and document that.

doc/primitives.dox

@@ -183,7 +183,7 @@ we now need some additional libraries, like `MeshTools` and `Primitives`,
 everything else is the same as previously:
 
 @dontinclude primitives/CMakeLists.txt
-@skip find_package(Magnum REQUIRED
+@skip find_package(
 @until Magnum::Shaders)
 
 You can now try using another primitive from @ref Primitives namespace or

doc/textured-triangle.dox

@@ -195,9 +195,10 @@ Compilation is slightly more complicated compared to previous examples, because
 we need to compile our resources into the executable.
 
 The `resources.conf` file lists all resources which need to be compiled into
-the executable --- that is our GLSL shader sources and the texture image. All
-resource groups need to have unique identifier by which they are accessed, we
-will use `textured-triangle-data` as above. As said above, the resource
+the executable --- that is our GLSL shader sources and the texture image (the
+one used in the above screenshot is [stone.tga](https://github.com/mosra/magnum-examples/raw/master/src/textured-triangle/stone.tga)).
+All resource groups need to have unique identifier by which they are accessed,
+we will use `textured-triangle-data` as above. As said above, the resource
 compilation process is explained thoroughly in Corrade's
 @ref resource-management "resource management tutorial".
 
@@ -214,15 +215,45 @@ After that we compile the resources using the
 @ref corrade-cmake-add-resource "corrade_add_resource()" macro and create an
 executable from the result and other source files. Last step is linking to all
 needed libraries. The plugin is loaded dynamically, so it's not handled by
-CMake at all.
+CMake in any way.
 
 @dontinclude textured-triangle/CMakeLists.txt
 @skip corrade_add_resource
 @until Magnum::Trade)
 
-You can now try playing around with the shader source, modifying texture
-coordinates or adding other effects. The full file content is linked below.
-Full source code is also available in the
+@m_class{m-block m-success}
+
+@par Enabling additional Magnum components in your project
+    If you're using the CMake subproject setup described in the
+    @ref getting-started "Getting Started Guide", you'll need to modify the
+    top-level `CMakeLists.txt` to enable the @ref Trade::TgaImporter "TgaImporter"
+    plugin as well. Because the plugins are loaded at runtime, CMake doesn't
+    know we need them to be built --- one option is to list them explicitly
+    like shown below, another (but uglier) is to not use `EXCLUDE_FROM_ALL` on
+    the magnum subdirectory, so everything is always built implicitly. The
+    plugin modules are placed into `Debug/lib/magnum-d/importers` (or
+    `Debug/bin/magnum-d/importers` on Windows) in the build directory and the
+    @ref Trade library will find them there on its own.
+@par
+    @code{.cmake}
+    ...
+
+    set(WITH_SDL2APPLICATION ON CACHE BOOL "" FORCE)
+    set(WITH_TGAIMPORTER ON CACHE BOOL "" FORCE)
+    add_subdirectory(magnum EXCLUDE_FROM_ALL)
+
+    # So the TgaImporter gets built implicitly
+    add_custom_target(plugins ALL DEPENDS Magnum::TgaImporter)
+    @endcode
+@par
+    If you're using a Magnum package, @ref Trade::TgaImporter "TgaImporter" is
+    included by default (and you don't need to do anything in CMake in order to
+    use it); if you build it yourself, make sure you have `WITH_TGAIMPORTER`
+    enabled.
+
+Once the application builds and starts, you can now try playing around with the
+shader source, modifying texture coordinates or adding other effects. The full
+file content is linked below. Full source code is also available in the
 [magnum-examples GitHub repository](https://github.com/mosra/magnum-examples/tree/master/src/textured-triangle).
 
 -   @ref textured-triangle/CMakeLists.txt "CMakeLists.txt"
@@ -240,6 +271,63 @@ contains additional patches for @ref CORRADE_TARGET_IOS "iOS",
 support that aren't present in `master` in order to keep the example code as
 simple as possible.
 
+@section examples-textured-triangle-importers PNG, JPEG and other file formats
+
+In an effort to keep the core Magnum repository small, it has support just for
+the TGA format. But it doesn't stop there, the
+@ref building-plugins "Magnum Plugins" repository provides support for many
+more file formats. Let's try loading arbitrary files instead --- the
+@ref Trade::AnyImageImporter "AnyImageImporter" plugin autodetects a file
+format and then delegates to a plugin that knows how to load PNGs. All you
+need to do is load it instead of @cpp "TgaImporter" @ce and then bundle a
+different file type --- or rewrite the example to take files from the
+filesystem instead:
+
+@code{.cpp}
+Containers::Pointer<Trade::AbstractImporter> importer =
+    manager.loadAndInstantiate("AnyImageImporter");
+if(!importer) std::exit(1);
+
+if(!importer->openFile("/path/to/myfile.jpg"))
+    std::exit(2);
+@endcode
+
+See @ref plugins for more information about how plugin loading and selection
+works. The next tutorial, @ref examples-viewer, expands further on this topic
+and also shows how to open files passed via command-line arguments.
+
+@m_class{m-block m-success}
+
+@par Enabling Magnum Plugins in your project
+    If you're using the CMake subproject setup described in the
+    @ref getting-started "Getting Started Guide", you'll need to modify the
+    top-level `CMakeLists.txt` to add Magnum Plugins as a subdirectory and
+    enable the new plugins. The @ref Trade::StbImageImporter "StbImageImporter"
+    is an universal dependency-less plugin that can handle PNGs, JPEGs and
+    other common files:
+@par
+    @code{.cmake}
+    ...
+
+    set(WITH_ANYIMAGEIMPORTER ON CACHE BOOL "" FORCE)
+    add_subdirectory(magnum EXCLUDE_FROM_ALL)
+
+    set(WITH_STBIMAGEIMPORTER ON CACHE BOOL "" FORCE)
+    # git clone https://github.com/mosra/magnum-plugins.git
+    add_subdirectory(magnum-plugins EXCLUDE_FROM_ALL)
+
+    add_custom_target(plugins ALL DEPENDS
+        Magnum::AnyImageImporter
+        MagnumPlugins::StbImageImporter)
+    @endcode
+@par
+    If you're using packaged Magnum, install
+    @ref building-plugins-packages "Magnum Plugins" the same way as you did with
+    Magnum, all the above-mentioned plugins are included by default (and you
+    don't need to do anything in CMake in order to use them). If you build it
+    yourself, make sure you have `WITH_ANYIMAGEIMPORTER` enabled for Magnum and
+    `WITH_STBIMAGEIMPORTER` enabled for Magnum Plugins.
+
 @example textured-triangle/CMakeLists.txt @m_examplenavigation{examples-textured-triangle,textured-triangle/} @m_footernavigation
 @example textured-triangle/resources.conf @m_examplenavigation{examples-textured-triangle,textured-triangle/} @m_footernavigation
 @example textured-triangle/TexturedTriangleExample.cpp @m_examplenavigation{examples-textured-triangle,textured-triangle/} @m_footernavigation

doc/triangle.dox

@@ -129,14 +129,10 @@ background:
 MAGNUM_APPLICATION_MAIN(TriangleExample)
 @endcode
 
-That's all, now we can compile the whole example using CMake. Apart from the
-standard CMake setup related to version requirements and paths to
-`FindMagnum.cmake`, `FindSDL2.cmake` and `FindCorrade.cmake`, as described in
-the @ref getting-started "Getting Started Guide", the setup is as follows.
-First we require the `Magnum` package with `GL`, `Shaders` and
-`Sdl2Application` components. It's recommended to also use Corrade's set of
-compiler flags to enable additional warnings. Then we create our executable and
-link to all Magnum libraries we requested. See @ref cmake for more information.
+That's all, now we can compile the whole example using CMake. Continuing from
+the @ref getting-started-review "Getting Started Guide", the only addition
+is finding & linking the @ref Magnum::Shaders library that's now being used as
+well:
 
 @dontinclude triangle/CMakeLists.txt
 @skip find_package
@@ -156,12 +152,14 @@ contains additional patches for @ref CORRADE_TARGET_IOS "iOS",
 support that aren't present in `master` in order to keep the example code as
 simple as possible.
 
-@m_div{m-note m-success} There's also an alternative version of this example
-that sidesteps the @ref Platform::Sdl2Application "Platform::Application"
-wrapper classes to show that it's possible to hook into OpenGL context and
-window surface provided by a third party library. See @ref examples-triangle-plain-glfw
-for details.
-@m_enddiv
+@m_class{m-note m-success}
+
+@par
+    There's also an alternative version of this example that sidesteps the
+    @ref Platform::Sdl2Application "Platform::Application" wrapper classes to
+    show that it's possible to hook into OpenGL context and window surface
+    provided by a third party library. See @ref examples-triangle-plain-glfw
+    for details.
 
 @example triangle/CMakeLists.txt @m_examplenavigation{examples-triangle,triangle/} @m_footernavigation
 @example triangle/TriangleExample.cpp @m_examplenavigation{examples-triangle,triangle/} @m_footernavigation

doc/viewer.dox

@@ -318,16 +318,59 @@ to talk about.
 Compilation is again nothing special:
 
 @dontinclude viewer/CMakeLists.txt
-@skip find_package(Magnum REQUIRED
+@skip find_package(
 @until Magnum::Trade)
 
+@m_class{m-block m-success}
+
+@par Enabling model-loading plugins in your project
+    The core Magnum repository contains a very rudimentary OBJ file loader in
+    @ref Trade::ObjImporter "ObjImporter", and you can try it with the
+    `scene.obj` file linked below. For more advanced models,
+    @ref building-plugins "Magnum Plugins" provide
+    @ref Trade::TinyGltfImporter "TinyGltfImporter" that can load the
+    `scene.gltf`, and there are more plugins for various other formats.
+@par
+    If you're using the CMake subproject setup, you'll need to modify the
+    top-level `CMakeLists.txt` to enable these --- expanding on what
+    @ref examples-textured-triangle-importers "was shown in the previous tutorial":
+@par
+    @code{.cmake}
+    ...
+
+    # If you want to load just basic OBJs
+    set(WITH_ANYIMAGEIMPORTER ON CACHE BOOL "" FORCE)
+    set(WITH_ANYSCENEIMPORTER ON CACHE BOOL "" FORCE)
+    set(WITH_OBJIMPORTER ON CACHE BOOL "" FORCE)
+    add_subdirectory(magnum EXCLUDE_FROM_ALL)
+
+    # If you want to load (textured) glTF as well
+    set(WITH_STBIMAGEIMPORTER ON CACHE BOOL "" FORCE)
+    set(WITH_TINYGLTFIMPORTER ON CACHE BOOL "" FORCE)
+    add_subdirectory(magnum-plugins EXCLUDE_FROM_ALL)
+
+    add_custom_target(plugins ALL DEPENDS
+        Magnum::AnyImageImporter
+        Magnum::AnySceneImporter
+        Magnum::ObjImporter
+        MagnumPlugins::StbImageImporter
+        MagnumPlugins::TinyGltfImporter)
+    @endcode
+@par
+    If you're using packaged Magnum, all the above-mentioned plugins are
+    included by default (and you don't need to do anything in CMake in order to
+    use them); if you build it yourself, make sure you have the desired
+    `WITH_*` options enabled.
+
 You can experiment by loading scenes of varying complexity and formats, adding
 light and camera property import or supporting more than just diffuse Phong
 materials. The full file content is linked below. Full source code is also
 available in the [magnum-examples GitHub repository](https://github.com/mosra/magnum-examples/tree/master/src/viewer).
 
 -   @ref viewer/CMakeLists.txt "CMakeLists.txt"
 -   @ref viewer/ViewerExample.cpp "ViewerExample.cpp"
+-   [scene.obj](https://github.com/mosra/magnum-examples/raw/master/src/viewer/scene.obj)
+-   [scene.gltf](https://github.com/mosra/magnum-examples/raw/master/src/viewer/scene.gltf)
 
 The [ports branch](https://github.com/mosra/magnum-examples/tree/ports/src/viewer)
 contains additional patches for @ref CORRADE_TARGET_EMSCRIPTEN "Emscripten"

src/viewer/scene.obj

@@ -0,0 +1,28 @@
+o Cube
+v 1.0 1.0 -1.0
+v 1.0 -1.0 -1.0
+v 1.0 1.0 1.0
+v 1.0 -1.0 1.0
+v -1.0 1.0 -1.0
+v -1.0 -1.0 -1.0
+v -1.0 1.0 1.0
+v -1.0 -1.0 1.0
+vn 0.0 1.0 0.0
+vn 0.0 0.0 1.0
+vn -1.0 0.0 0.0
+vn 0.0 -1.0 0.0
+vn 1.0 0.0 0.0
+vn 0.0 0.0 -1.0
+s off
+f 5//1 3//1 1//1
+f 3//2 8//2 4//2
+f 7//3 6//3 8//3
+f 2//4 8//4 6//4
+f 1//5 4//5 2//5
+f 5//6 2//6 6//6
+f 5//1 7//1 3//1
+f 3//2 7//2 8//2
+f 7//3 5//3 6//3
+f 2//4 4//4 8//4
+f 1//5 3//5 4//5
+f 5//6 1//6 2//6