Resolve Slider Performance Degradation on NI CompactRIO Embedded UI

Issue Details

When using a CompactRIO (cRIO) chassis with an embedded User Interface and a connected display, placing a Slider control on the Front Panel causes a noticeable drop in rendering frame rate. The UI becomes sluggish or visually unresponsive during operation. This is most apparent on a Tab Control that contains multiple Slider controls, where switching between Tab Pages introduces significant loading times. 

Environment: LabVIEW 2020 SP1 or later CompactRIO controller with embedded UI (for example, cRIO 9035) NI Linux Real Time

Solution

The root cause is the way LabVIEW renders Slider controls. On embedded targets with limited processing power and no GPU acceleration, the antialiasing computations for Slider drawing consume a disproportionate share of the rendering budget. This causes frame drops and delayed visual updates on the Image control.

There are two solutions. Use whichever fits your situation.

Option A: Upgrade LabVIEW (Recommended)

1. Upgrade your LabVIEW installation and NI Linux RT drivers to LabVIEW 2026 Q1 or later. This version includes a fix for the Slider rendering performance issue on RT targets.
2. Redeploy your application to the CompactRIO target after upgrading.

Option B: Disable Antialiasing on the RT Target

Use this approach if you cannot upgrade to LabVIEW 2026 Q1.

1. Open a terminal on your host machine and connect to the CompactRIO target through SSH: ssh admin@<target-ip-address>
2. Install a text editor if one is not already present. For nano, run: opkg update opkg install nano
3. Open the lvrt.conf file in the text editor: sudo nano /etc/natinst/shared/lvrt.conf Alternatively, use vi: sudo vi /etc/natinst/shared/lvrt.conf
4. Add the following line on an empty line in the file: SmoothLineDrawing=False
5. Save the file and exit the text editor.
6. Reboot the CompactRIO target to apply the change: sudo reboot

After upgrading (Option A) or disabling antialiasing (Option B), the Slider controls render without the excessive frame rate drop. Tab Page switching with multiple Sliders becomes responsive. 

Additional Information

If you choose Option B, note that disabling SmoothLineDrawing affects all line and shape rendering on the target, not just Sliders. Inspect your UI for any visual quality changes on other controls. If the visual tradeoff is not acceptable, consider upgrading to LabVIEW 2026 Q1 as a permanent fix.

This issue does not occur on desktop targets with standard GPU acceleration. It is specific to embedded Linux RT targets rendering through the software pipeline.