What is this
The aim is to implement libopenvr_api.dll/libopenvr_api.so on top of a libre runtime like OpenHMD or OSVR SDK.
Games and applications using the OpenVR API ship the libopenvr_api.so library or rely on it to be present in /usr/lib/.
Valve's libopenvr_api.so is a wrapper. It loads the implementation of the OpenVR classes from their closed source and x86-only SteamVR runtime. However, libopenvr_api is documented and "open source", so other backends than SteamVR can be implemented like OpenHMD or OSVR.
Once this library is finished, the libopenvr_api shipped in any SteamVR application or game can be swapped out with this one and the application can be used with only the OSVR or OpenHMD drivers, Steam and SteamVR are not needed.
Status
Note: hellovr_opengl draws upside down in its preview window. That's not a bug of this libopenvr_api, hellovr_opengl upstream should fix that.
OpenHMD
Rendering
Creates fullscreen window with the HMD's resolution via SDL and displays the textures side by side.
Orientation Tracking
The HMD is hardcoded as deviceindex 0, controller support has to wait until the HMD tracking works.
Three matrices are used by hellovr_opengl:
General setup: GetProjectionMatrix() is glm::perspective() GetEyeToHeadTransform() - currently identity matrix
HMD orientation that gets updated every frame: WaitGetPoses() - hmd quaternion converted to matrix
TODO
- apply OpenHMD's distortion shader before displaying the textures
- Check all the matrices (I think the cubes are too big but could be coincidence)
- Controllers, wait for OpenHMD's controller API
OSVR
Rendering
not much yet
Orientation Tracking
TODO
Check positional tracking in WaitGetPoses.
How to use and hack it
git clone --recursive https://github.com/ChristophHaag/openvr_api-libre
cd openvr_api-libre
cmake .
make -j12
./hellovr_opengl
hellovr_opengl is linked to libopenvr_api.so in the same directory, no special setup needed when you already have it in /usr/lib.
You can customize the build with cmake -DOPENHMD_LIBOPENVR=OFF and cmake -DOSVR_LIBOPENVR=OFF. At runtime you can choose one of the backends with the environment variable OPENVR_BACKEND=OPENHMD or OPENVR_BACKEND=OSVR.
openvr_api_public.cpp is the main file of the library. The implementation of the classes is in openvr_osvr.h and openvr_openhmd.h. Not all classes and many methods are not implemented.