More helpful README update.
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README.md
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README.md
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@ -5,10 +5,82 @@ venerable [FBX](https://www.autodesk.com/products/fbx/overview) format to
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[glTF 2.0](https://github.com/KhronosGroup/glTF/tree/master/specification/2.0),
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a modern runtime asset delivery format.
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## Building & Running
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Precompiled binaries releases may be
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found [here](https://github.com/facebookincubator/FBX2glTF/releases).
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This tool has been tested on Linux, Mac OS X and Windows. It requires CMake 3.5+
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and a reasonably C++11 compliant toolchain.
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## Running
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The tool can be invoked like so:
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```
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> FBX2glTF ~/models/butterfly.fbx
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```
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Or perhaps, as part of a more complex pipeline:
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```
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> FBX2glTF --binary --draco --flip-v \
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--khr-materials-common \
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--input ~/models/source/butterfly.fbx \
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--output ~/models/target/butterfly.glb
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```
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### CLI Switches
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You can always run the binary with --help to see what options it takes:
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```
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FBX2glTF 2.0: Generate a glTF 2.0 representation of an FBX model.
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Usage:
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FBX2glTF [OPTION...] [<FBX File>]
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-i, --input arg The FBX model to convert.
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-o, --output arg Where to generate the output, without suffix.
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-e, --embed Inline buffers as data:// URIs within
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generated non-binary glTF.
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-b, --binary Output a single binary format .glb file.
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-d, --draco Apply Draco mesh compression to geometries.
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--flip-u Flip all U texture coordinates.
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--flip-v Flip all V texture coordinates.
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--khr-materials-common (WIP) Use KHR_materials_common extensions to
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specify Unlit/Lambert/Blinn/Phong shaders.
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--pbr-metallic-roughness (WIP) Try to glean glTF 2.0 native PBR
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attributes from the FBX.
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--pbr-specular-glossiness
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(WIP) Experimentally fill in the
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KHR_materials_pbrSpecularGlossiness extension.
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-k, --keep-attribute arg Used repeatedly to build a limiting set of
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vertex attributes to keep.
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-v, --verbose Enable verbose output.
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-h, --help Show this help.
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-V, --version Display the current program version.
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```
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Some of these switches are not obvious:
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- `--embed` is the way to get a single distributable file without using the
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binary format. It encodes the binary buffer(s) as a single enormous
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base64-encoded `data://` URI. This is a very slow and space-consuming way to
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accomplish what the binary format was invented to do simply and efficiently,
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but it can be useful e.g. for loaders that don't understand the .glb format.
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- `--flip-u` and `--flip-v`, when enabled, will apply a `x -> (1.0 - x)`
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function to all `u` or `v` texture coordinates respectively. The `u` version
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is perhaps not commonly used, but flipping `v` is recommended. Your FBX is
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likely constructed with the assumption that `(0, 0)` is bottom left, whereas
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glTF has `(0, 0)` as top left. To produce spec-compliant glTF, you will want
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to pass `--flip-v`.
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- All three material options are, in their own way, works in progress. The
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`--pbr-metallic-roughness` switch will be chosen by default if you supply
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none of the others, and is the only one that produces glTF that does not
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depend on an extension. It is documented further below, as is
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`--khr-materials-common`.
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- If you supply any `-keep-attribute` option, you enable a mode wherein you must
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supply it repeatedly to list *all* the vertex attributes you wish to keep in
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the conversion process. This is a way to trim the size of the resulting glTF
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if you know the FBX contains superfluous attributes. The supported arguments
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are `position`, `normal`, `tangent`, `color`, `uv0`, and `uv1`.
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## Building it on your own
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This build process has been tested on Linux, Mac OS X and Windows. It requires
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CMake 3.5+ and a reasonably C++11 compliant toolchain.
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We currently depend on the open source projects
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[Draco](https://github.com/google/draco),
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@ -31,23 +103,11 @@ Compilation on Unix machines should be as simple as:
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```
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> cd <FBX2glTF directory>
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> cmake -H. -Bbuild
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> make -Cbuild
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> cmake -H. -Bbuild -DCMAKE_BUILD_TYPE=Release
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> make -Cbuild -j4 install
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```
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If all goes well, you will end up with a statically linked executable that can
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be invoked like so:
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```
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> ./build/FBX2glTF ~/models/butterfly.fbx
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```
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Or perhaps, as part of a more complex pipeline:
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```
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> ./build/FBX2glTF --binary --draco --flip-v \
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--khr-materials-common \
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--input ~/models/source/butterfly.fbx \
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--output ~/models/target/butterfly.glb
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```
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If all goes well, you will end up with a statically linked executable.
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### Windows
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