The focus of this guide is on using Streamline to integrate Reflex into an application. For more information about Reflex itself, please visit the NVIDIA Developer Reflex Page For information on user interface considerations when using this plugin, please see the "RTX UI Developer Guidelines.pdf" document included with this SDK.
Here is an overview list of sub-features in the Reflex plugin:
Feature GPU Vendor GPU HW Driver Version Support Check Key Setting/Marker
NOTE:
The sub-features are distinct to each other without any cross-dependencies. Everything is abstracted within the plugin and is transparent to the application. The application should not explicitly check for GPU HW, vendor, and driver version. The application should do everything the same regardless of sub-feature support and enablement. The only 2 exceptions are Reflex UI and Reflex Flash Indicator (RFI). The application must disable Reflex UI based on
sl::ReflexSettings::lowLatencyAvailable
. And the application must not send
sl::PCLMarker::eTriggerFlash
when
sl::ReflexSettings::flashIndicatorDriverControlled
is false.
Call
slInit
as early as possible (before any dxgi/d3d11/d3d12 APIs are invoked)
sl::Preferences pref{};
pref.showConsole = true; // for debugging, set to false in production
pref.logLevel = sl::LogLevel::eDefault;
pref.pathsToPlugins = {}; // change this if Streamline plugins are not located next to the executable
pref.numPathsToPlugins = 0; // change this if Streamline plugins are not located next to the executable
pref.pathToLogsAndData = {}; // change this to enable logging to a file
pref.logMessageCallback = myLogMessageCallback; // highly recommended to track warning/error messages in your callback
pref.applicationId = myId; // Provided by NVDA, required if using NGX components (DLSS 2/3)
pref.engine = myEngine; // If using UE or Unity
pref.engineVersion = myEngineVersion; // Optional version
pref.projectId = myProjectId; // Optional project id
if(SL_FAILED(res, slInit(pref)))
// Handle error, check the logs
if(res == sl::Result::eErrorDriverOutOfDate) { /* inform user */}
// and so on ...
For more details please see preferences
Call slShutdown()
before destroying dxgi/d3d11/d3d12/vk instances, devices and other components in your engine.
if(SL_FAILED(res, slShutdown()))
// Handle error, check the logs
Once the main device is created call slSetD3DDevice
or slSetVulkanInfo
:
if(SL_FAILED(res, slSetD3DDevice(nativeD3DDevice)))
// Handle error, check the logs
As soon as SL is initialized, you can check if Reflex is available for the specific adapter you want to use:
Microsoft::WRL::ComPtr<IDXGIFactory> factory;
if (SUCCEEDED(CreateDXGIFactory(__uuidof(IDXGIFactory), (void**)&factory)))
Microsoft::WRL::ComPtr<IDXGIAdapter> adapter{};
uint32_t i = 0;
while (factory->EnumAdapters(i, &adapter) != DXGI_ERROR_NOT_FOUND)
DXGI_ADAPTER_DESC desc{};
if (SUCCEEDED(adapter->GetDesc(&desc)))
sl::AdapterInfo adapterInfo{};
adapterInfo.deviceLUID = (uint8_t*)&desc.AdapterLuid;
adapterInfo.deviceLUIDSizeInBytes = sizeof(LUID);
if (SL_FAILED(result, slIsFeatureSupported(sl::kFeatureReflex, adapterInfo)))
// Requested feature is not supported on the system, fallback to the default method
switch (result)
case sl::Result::eErrorOSOutOfDate: // inform user to update OS
case sl::Result::eErrorDriverOutOfDate: // inform user to update driver
case sl::Result::eErrorNoSupportedAdapter: // cannot use this adapter (older or non-NVDA GPU etc)
// and so on ...
// Feature is supported on this adapter!
IMPORTANT:
The Reflex plugin includes two distinct functionalities: Reflex Low Latency and PC Latency (PCL) Stats. While the support for Reflex Low Latency is dependent on the GPU hardware, vendor, and driver version, PCL Stats is supported on all GPU hardwares, vendors, and driver versions. The plugin handles all such abstractions; As long as sl::kFeatureReflex
is supported, the application should always make the same slPCLSetMarker
and slReflexSleep
calls without any explicit GPU hardware, vendor, and driver version checks.
To find out what latency modes are available, currently active or to obtain the latest latency stats you can do the following:
// Using helpers from sl_reflex.h
sl::ReflexState state{};
if(SL_FAILED(res, slReflexGetState(state)))
// Handle error here, check the logs
if(state.lowLatencyAvailable)
// Reflex Low Latency is available, on NVDA hardware this would be done through Reflex.
// The application can show the Reflex Low Latency UI. (Otherwise hide/disable the UI.)
// This is for UI only. Do everything else the same, even when this is false.
if(state.flashIndicatorDriverControlled)
// Reflex Flash Indicator (RFI) is controlled by the driver. This means
// the application should always check for left mouse button clicks and
// send the trigger flash markers accordingly. The driver will decide
// whether to show the RFI on screen based on user preference.
To configure Reflex please do the following:
// Using helpers from sl_reflex.h
sl::ReflexOptions reflexOptions = {};
reflexOptions.mode = eLowLatency; // enable Reflex low-latency mode, or eOff to disable, eLowLatencyWithBoost for "On + Boost"
reflexOptions.frameLimitUs = myFrameLimit; // See docs for ReflexConstants
if(SL_FAILED(res, slReflexSetOptions(reflexOptions)))
// Handle error here, check the logs
NOTE:
To turn off Reflex set sl::ReflexOptions.mode
to sl::ReflexMode::eOff
. slPCLSetMarker
must always be called even when Reflex low-latency mode is Off. These markers are also used by PCL Stats to measure latency.
NOTE:
For Reflex "On + Boost" set sl::ReflexOptions.mode
to sl::ReflexMode::eLowLatencyWithBoost
.
NOTE:
slReflexSetOptions
needs to be called at least once, even when Reflex Low Latency is Off and there is no Reflex UI. If options do not change there is no need to call this method every frame.
Call slReflexSleep
at the appropriate location where your application should sleep.
Here is some pseudo code:
// Using helpers from sl_reflex.h
// When your application should sleep to achieve optimal low-latency mode
if(useReflex)
// Sleep
if(SL_FAILED(res, slReflexSleep(*currentFrame)))
// Handle error
Reflex requires you also integrate PCL Stats
Existing Reflex integrations can be easily converted to use SL Reflex by following these steps:
Remove NVAPI from your application
Remove reflexstats.h
from your application
There is no longer any need to provide a native D3D/VK device when making Reflex calls - SL takes care of that, hence making the integrations easier
NvAPI_D3D_SetSleepMode
is replaced with set reflex options
NvAPI_D3D_GetSleepStatus
is replaced with get reflex state - see sl::ReflexState::lowLatencyAvailable
NvAPI_D3D_GetLatency
is replaced with get reflex state - see sl::ReflexReport
NvAPI_D3D_SetLatencyMarker
is replaced with slPCLSetMarker
NvAPI_D3D_Sleep
is replaced with slReflexSleep
NVSTATS*
calls are handled automatically by SL Reflex plugin and are GPU agnostic
NVSTATS_IS_PING_MSG_ID
is replaced with get reflex state - see sl::ReflexOptions::statsWindowMessage
Checklist
Please use this checklist to confirm that your Reflex integration has been completed successfully. While this list is not comprehensive and does not replace rigorous testing, it should help to identify obvious issues.
Checklist Item
Pass/Fail
Download/uncompress Reflex Verification tools
https://developer.download.nvidia.com/assets/gamedev/files/ReflexVerification.zip
Install FrameView SDK
Double click the FrameView SDK Installer (FVSDKSetup.exe
)
Restart the system
Run ReflexTestSetup.bat
from an administrator mode command prompt
This will force the Reflex Flash Indicator to enable, enable the Verification HUD, set up the Reflex Test framework, and start ReflexTest.exe.
Check Reflex Low Latency modes
Run game
Make sure game is running in fullscreen exclusive
Make sure VSYNC is disabled
Make sure MSHybrid mode is not enabled
Check Reflex Low Latency’s default state is On in UI and in the Verification HUD
Use the Reset / Default button in UI if it exists
Cycle through the three (3) Reflex modes in UI ("Off", "On", and "On + Boost") and check that it matches with “Reflex Mode” in the Verification HUD
Running Reflex Tests
For titles with DLSS Frame Generation (FG), turn FG to On
Press Alt + t
in game to start the test (2 beeps)
Analyze results after the test is done (3 beeps)
Test should take approximately 5 minutes
Check for warnings in the ReflexTest.exe output
Press Alt + t
in game to start the test (2 beeps)
Analyze results after the test is done (3 beeps)
Test should take approximately 5 minutes
Check for warnings in the ReflexTest.exe output
Press Alt + t
in game to start the test (2 beeps)
Analyze results after the test is done (3 beeps)
Test should take approximately 5 minutes
Check for warnings in the ReflexTest.exe output
Turn Reflex to Off
Look at the Verification HUD to ensure that the markers are still updating
Test the Reflex Flash Indicator
Verify the Reflex Flash Indicator is showing
Notice the gray square that flashes when the left mouse button is pressed
Verify that Flash Indicator in the Verification HUD increments by 1 when the left mouse button is pressed
Run capturePclEtw.bat
in administrator mode command prompt
Go back to the game. Start game play
Check the Keybinding menu to make sure F13 is not being automatically applied when selecting a key
Go back to the command prompt and press any key to exit the bat
Run ReflexTestCleanUp.bat
in administrator mode command prompt
* This disables the Reflex Flash Indicator and the Reflex Test framework
Test on other IHV (if available)
Install other IHV hardware
Install FrameView SDK and restart the system
Run PrintPCL.exe
in administrator mode command prompt
Run game
Press Alt + t
in game
Look at the PCL value in the command prompt. If the value is not 0.0, then PCL is working
Press Ctrl + c
in the command prompt to exit PrintPCL.exe
Check to make sure Reflex UI is not available
Send NVIDIA Reflex Test report and Checklist results
Send to NVIDIA alias: [email protected]
ReflexTestResults.txt
The Reflex Test Utility iterates through (up to) 10 FPS points, measuring PCL. Here is an example of the report summary:
*** Summary [647e5c14] - Reflex ON, Frame Gen x2, I>S S>Q Q>R R>FG FG>D
252.5 FPS: PCL 23.4 ms is PASS at 5.91 FT! -0.4% FPS impact. 34.0% latency reduction. {0.96 1.42 1.95 0.43 0.66}
236.4 FPS: PCL 24.1 ms is PASS at 5.71 FT! -0.5% FPS impact. 36.0% latency reduction. {0.91 1.33 1.93 0.42 0.62}
213.3 FPS: PCL 26.0 ms is PASS at 5.54 FT! 0.1% FPS impact. 39.7% latency reduction. {1.00 1.16 1.90 0.42 0.57}
197.2 FPS: PCL 27.3 ms is PASS at 5.39 FT! -0.4% FPS impact. 40.3% latency reduction. {0.99 0.99 1.91 0.41 0.58}
177.4 FPS: PCL 28.9 ms is PASS at 5.13 FT! -0.9% FPS impact. 42.8% latency reduction. {0.96 0.85 1.89 0.41 0.52}
160.5 FPS: PCL 32.6 ms is PASS at 5.24 FT! 0.2% FPS impact. 42.8% latency reduction. {1.11 0.74 1.95 0.41 0.53}
145.0 FPS: PCL 33.5 ms is PASS at 4.85 FT! -0.1% FPS impact. 46.7% latency reduction. {0.97 0.70 1.84 0.41 0.43}
121.3 FPS: PCL 38.8 ms is PASS at 4.70 FT! -1.2% FPS impact. 47.5% latency reduction. {1.10 0.47 1.87 0.40 0.36}
59.6 FPS: PCL 68.0 ms is PASS at 4.06 FT! -0.4% FPS impact. 55.1% latency reduction. {0.93 0.21 1.78 0.40 0.23}
44.1 FPS: PCL 94.9 ms is PASS at 4.18 FT! -1.3% FPS impact. 52.6% latency reduction. {1.29 0.16 1.73 0.40 0.16}
PASS/OKAY/WARN
This is a sanity check on PCL. WARN indicates a possible issue with the integration.
PCL expressed in average frame times. (E.g., 23.4 / 1000 * 252.5 = 5.91 FT)
FPS impact
Average FPS difference between Reflex On (+ Boost) vs Off.
A negative value means Reflex lowers/worsens FPS.
Latency reduction
Average PCL difference between Reflex On (+ Boost) vs Off.
A positive value means Reflex lowers/improves latency.
Input to simulation start latency in average frame times.
Simulation start to queue start latency in average frame times.
Queue start to GPU end (or DLSS FG start) latency in average frame times.
DLSS FG start to GPU end latency in average frame times.
R>D/FG>D
GPU end to displayed latency in average frame times.
Reflex Verification HUD
The Reflex Verification HUD can be used to help validate your integration for correctness.
ReflexTestEnable.exe 1 [xpos ypos]
Display the Reflex Verification HUD in your game. Optional arguments xpos and ypos specify the on-screen position of the HUD.
ReflexTestEnable.exe 0
Hide the Reflex Verification HUD.
For the commands to take effect, a restart of the game is required.
NOTE:
Reflex Verification HUD requires 531.18 driver or newer.
If the Verification HUD does not appear, you will need to add the game to the app profile: NVIDIA Control Panel -> 3D Settings -> Program Settings -> Select Program to Customize -> Add -> Select a program -> Add Selected Program -> Apply.
Fields are as follows:
Field
Value
Details
Simulation Interval
Duration
Simulation start time of frame X - simulation start time of
frame X-1
All other timestamps are relative to simulation start time
Simulation End Time
Timestamp
Simulation end marker time
Render Start/End Time
Timestamp
Render submit start/end marker time
Present Start/End Time
Timestamp
Present start/end marker time
Driver Start/End Time
Timestamp
Start = first buffer submission
End = last present submission
OS Queue Start/End Time
Timestamp
Start = first significant buffer submission
End = GPU end time
GPU Start/End Time
Timestamp
Start = GPU rendering starts; End = GPU rendering ends