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This guide describes basic testing and performance analysis for Oculus Go development in Unreal.
VR application debugging is a matter of getting insight into how the application is structured and executed, gathering data to evaluate actual performance, evaluating it against expectation, then methodically isolating and eliminating problems.
When analyzing or debugging, it is crucial to proceed in a controlled way so that you know specifically what change results in a different outcome. Focus on bottlenecks first. Only compare apples to apples, and change one thing at a time (e.g., resolution, hardware, quality, configuration).
Always be sure to profile, as systems are full of surprises. We recommend starting with simple code, and optimizing as you go - don’t try to optimize too early.
Before debugging performance problems, establish clear targets to use as a baseline for calibrating your performance.
These targets can give you a sense of where to aim, and what to look at if you’re not making frame rate or are having performance problems.
Below you will find some general guidelines for establishing your baselines, given as approximate ranges unless otherwise noted.
Display Refresh Rate
The Unreal Editor provides a built-in Profiler Tool that provides performance metrics for your app.
Oculus has added the ‘Oculus System Metrics’ section of the Profiler Tool to provide real-time VR specific metrics.
The following metrics are available-
The first step of the performance optimization is often determining if the bottleneck is on the CPU or GPU. This can be difficult to determine on Android applications because of difficulty obtaining GPU timing. When the application is running on the Oculus Go with the Profiler Tool, you are able to read the GPU cost to both the application and the VR compositor. If the total GPU time is close or equal to the frame time, the application is likely GPU bound. Otherwise, the bottleneck is CPU.
Applications can use multiple cores simultaneously on the Oculus Go. The Profiler Tool gathers both the utility percentage on the most occupied CPU core and the average utility percentage among all CPU cores. If the “System CPU Util Worst%” is very high but the “System CPU Util Avg%” is relatively low, that often means opportunity to optimize the application by rebalancing workload among threads.
OVR Metrics Tool reports application frame rate, heat, GPU and CPU throttling values, and the number of tears and stale frames per second. It is available for download from our Downloads page.
OVR Metrics Tool can be run two modes. In Report Mode, it displays performance report about a VR session after it is complete. Report data may be easily exported as a CSV and PNG graphs.
In Performance HUD Mode, OVR Metrics Tool renders performance graphs as a VR overlay over any running Oculus application.
For more information, see OVR Metrics Tool in our Mobile SDK Guide.
Oculus branches of Unreal add support for debugging mobile sessions using ndk-gdb, a small shell script wrapped around GNU GDB that is included with the Android NDK.
Using ndk-gdb from the command line adds convenient features to your debugging workflow by allowing, for example, adding breakpoints, stepping through code, and inspecting variables with a command line interface.
To use ndk-gdb for debugging:
For more information on using GDB for debugging, see the GNU GDB documentation.
Reports complete Android system utilization. It is available here: http://developer.android.com/tools/help/systrace.html
The Oculus Go is based on a Qualcomm chip set, so you can use the Snapdragon Profiler.
Mac OpenGL Monitor
An OpenGL debugging and optimizing tool for OS X. Available here: https://developer.apple.com/library/mac/technotes/tn2178/_index.html#//apple_ref/doc/uid/DTS40007990
For detailed information about Oculus development, go to:
Visit our developer support forums at https://forums.oculusvr.com/developer/.
Our Support Center can be accessed at https://support.oculus.com.