Add Velocity calculation logic and GUI toggle (end-to-end MVP). by M1DNYT3 · Pull Request #1753 · SlimeVR/SlimeVR-Server

M1DNYT3 · 2026-02-17T12:00:27Z

This PR completes velocity transmission end-to-end, adding RPC settings and a GUI toggle on top of the foundation from #1754.

What's added:

Protobuf velocity transmission via ProtobufBridge, per-tracker
RPC settings support - toggle persists across restarts
GUI toggle in General Settings with i18n

Toggle's GUI Path:
Settings > General > Tracker Settings > Toggle is at the very bottom of the section.

Technicalities:
Most of the line count (~400) comes from regenerated ProtobufMessages.java. The handwritten change itself is small.

Depends on SlimeVR/SolarXR-Protocol#202, should be merged only after the submodule is updated to the tracked HEAD.

Addresses the issue: #25

M1DNYT3 · 2026-02-17T12:38:57Z

Force pushes in history are changes made by spotless.
For some reason, one application wasn't enough for it to fix all the issues in Tracker.kt, so I had to push it twice, and I didn't want to make 2 separate commits for spotless alone.

M1DNYT3 · 2026-03-20T22:17:05Z

At some point, I had a conversation with @ButterscotchV in DMs, and there was a recommendation expressed to ship the whole feature (Implying a toggle, nothing overkill) in one PR.

The description is edited accordingly to reflect each affected part of the code.
The handwritten part (meaning not regenerated flatbuf, and not regenerated ProtobufMessages) follows the existing code architecture 1:1 and reuses the methods, styles, and classes, where necessary.

M1DNYT3 · 2026-04-22T16:05:13Z

I had some additional feedback from @ButterscotchV in DMs, addressed it all + rebased to the latest main + also did some changes of my own.

Feedback changes:

drop applyVelocityPolicyTo() in VRServer.kt; initially made for expandability, but turned out to be redundant because VRConfig.applyVelocityPolicy() already covers expandability.
replace System.nanoTime() with Kotlin's TimeSource; self-explaining, did precisely that.

My own improvement:
Noticed that I forgot to wire hasVelocity instead of allowVelocity in the ProtobufBridge.kt; the former was created for a safeguard to not send anything if we don't have any velocity in the tracker. Technically, both calls would result in the same behavior, but hasVelocity follows architecture better and explicitly states that there has to be something for it to be sent, whereas allowVelocity simply states whether the toggle is on or off.

M1DNYT3 · 2026-04-24T11:25:53Z

Review changes were shipped and tested E2E with SteamVR.

One thing to note. Jitter is still noticeable. I may think of a one-euro filter or some velocity smoothing added, but I suggest that to be a separate PR once this one is shipped.

ButterscotchV

Looks fine, SolarXR needs to be merged/fixed before this PR.

ImSapphire · 2026-04-27T22:23:02Z

+	// Disables derived velocity for all trackers. Driver zeroes out velocity if nothing is returned in protobuf message.
+	var sendDerivedVelocity: Boolean = false
+
+	fun updateTrackersVelocityPolicy() {


"policy" is a wording not used in the rest of the codebase and was confusing for me on the first read. This should probably be named updateTrackersVelocitySettings, like in ResetsConfig.

ImSapphire · 2026-04-27T22:35:51Z

+	/**
+	 * Updates the derived velocity of the tracker by differentiating position over time.
+	 *
+	 * This method enforces the [allowVelocity] policy and checks for valid position data before
+	 * proceeding. If conditions are met, it calculates velocity based on the displacement since the
+	 * last update, applying a sanity check on the time delta to filter out noise and ensure data stability.
+	 *
+	 */


Could be shortened

Suggested change

/**

* Updates the derived velocity of the tracker by differentiating position over time.

*

* This method enforces the [allowVelocity] policy and checks for valid position data before

* proceeding. If conditions are met, it calculates velocity based on the displacement since the

* last update, applying a sanity check on the time delta to filter out noise and ensure data stability.

*

*/

/**

* If derived velocity is enabled, updates the derived velocity of the tracker, calculating it based on the position displacement

* since the last update, applying a sanity check on the time delta to filter out noise and ensure data stability.

*

*/

I'm not sure why this is not showing up as an outdated comment, and also doesn't show up in the diff for the PR.
If looking directly at my base branch, you can see the update: https://github.com/M1DNYT3/SlimeVR-Server-NaLo-Support/blob/c9c750230ea73da399fbad0276fd919647b8bea8/server/core/src/main/java/dev/slimevr/tracking/trackers/Tracker.kt#L369

Hell, even a rebase didn't help. Seems like an issue on GitHub's end.

Anyway, both comments are addressed and the branch is rebased to the latest main, so the merge should be clean now.

… latest definition from the Driver's main branch.

…ce, Replace allowVelocity with hasVelocity in ProtobufBridge.

…#1811 # Conflicts: # server/core/src/main/java/dev/slimevr/protocol/rpc/settings/RPCSettingsBuilder.kt

� Conflicts: � server/core/src/main/java/dev/slimevr/protocol/rpc/settings/RPCSettingsBuilder.kt

…timing fix, non-nullable writeTrackerUpdate param

…dVelocity KDoc

M1DNYT3 requested review from ButterscotchV, Eirenliel and Erimelowo as code owners February 17, 2026 12:00

github-actions Bot added Area: Skeletal Model Deals with the model of the skeleton and its pose Area: Server Related to the server labels Feb 17, 2026

M1DNYT3 force-pushed the velocity-mvp branch 3 times, most recently from b502b9c to b83d03d Compare February 17, 2026 12:26

M1DNYT3 mentioned this pull request Feb 17, 2026

Velocity MVP. Protobuf Bridge and Messages Update for Velocity Data Exchange. #1754

Closed

M1DNYT3 changed the title ~~MVP. Add Velocity transmission toggle and calculation logic.~~ MVP. Add Velocity calculation toggle and logic. Feb 17, 2026

M1DNYT3 changed the title ~~MVP. Add Velocity calculation toggle and logic.~~ Velocity MVP. Add Velocity calculation toggle and logic. Feb 17, 2026

M1DNYT3 mentioned this pull request Mar 6, 2026

Natural Locomotion support #25

Open

M1DNYT3 force-pushed the velocity-mvp branch from b83d03d to 501e54e Compare March 20, 2026 21:57

M1DNYT3 requested review from ImSapphire and loucass003 as code owners March 20, 2026 21:57

github-actions Bot added Area: Application Protocol Related to communication with apps like the GUI, overlay, games Area: GUI Related to the GUI Area: Translation Improvements or additions to translations Area: SteamVR Driver Related to the SteamVR Driver labels Mar 20, 2026

M1DNYT3 mentioned this pull request Mar 20, 2026

Added VelocitySettings to RPC schema SlimeVR/SolarXR-Protocol#202

Merged

M1DNYT3 changed the title ~~Velocity MVP. Add Velocity calculation toggle and logic.~~ Add Velocity calculation logic and GUI toggle (end-to-end MVP). Mar 20, 2026

M1DNYT3 force-pushed the velocity-mvp branch 2 times, most recently from b3df88e to fc9c9a6 Compare April 22, 2026 15:58

ButterscotchV requested changes Apr 24, 2026

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M1DNYT3 requested a review from ButterscotchV April 24, 2026 11:26

ButterscotchV requested changes Apr 24, 2026

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Comment thread server/core/src/main/java/dev/slimevr/tracking/trackers/Tracker.kt Outdated

Comment thread server/core/src/main/java/dev/slimevr/tracking/trackers/Tracker.kt Outdated

ButterscotchV approved these changes Apr 24, 2026

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ButterscotchV added Status: Blocked by other issue Progress cannot be made until linked issue is resolved and removed Status: Blocked by other issue Progress cannot be made until linked issue is resolved labels Apr 24, 2026

ImSapphire reviewed Apr 27, 2026

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M1DNYT3 added 12 commits April 28, 2026 12:13

Add Velocity transmission toggle and calculation logic.

6577987

Add Velocity data send via ProtobufBridge. Update ProtobufMessages to…

15aa4f4

… latest definition from the Driver's main branch.

Added velocity transmission toggle to GUI and RPC (NaLo support)

369991a

Remove applyVelocityPolicyTo(), Replace System.nanoTime with Timesour…

3a53ccc

…ce, Replace allowVelocity with hasVelocity in ProtobufBridge.

Add build stubs for solarxr-protocol schema additions pending SlimeVR…

40089e0

…#1811 # Conflicts: # server/core/src/main/java/dev/slimevr/protocol/rpc/settings/RPCSettingsBuilder.kt

Add FBT jitter warning to velocity settings description

3d111ab

� Conflicts: � server/core/src/main/java/dev/slimevr/protocol/rpc/settings/RPCSettingsBuilder.kt

Fix RPC velocity toggle state being sent to response instead of request

6427535

Review: Inlined velocity policy, non-nullable velocityState, markNow …

cfab5bc

…timing fix, non-nullable writeTrackerUpdate param

Review: velocityState direct use and change to val

c8ad726

Solar: sync with the updated head

c2c6675

Update solarxr to track main.

ec178b6

Review: rename updateTrackersVelocityPolicy and rephrase updateDerive…

76d087e

…dVelocity KDoc

M1DNYT3 force-pushed the velocity-mvp branch from c9c7502 to 76d087e Compare April 28, 2026 09:13

M1DNYT3 requested a review from ImSapphire April 28, 2026 09:21

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