[Bug] RigidBody3D stutters/lags when colliding with Continuous CD enabled

[JoshuaWeissTBS]

Describe the bug

When a RigidBody3D collides it appears to stutter or lag. This only happens on the Fast SIMD version of Rapier 3d, and only when Continuous CD is enabled on the rigid body.

Here's a video in the MRP. Notice how it stutters upon one touching the ground before the other side falls:

2026-04-01.16-36-49.mp4

Here's a more obvious video of it in my actual game. Observe how it does not smoothly slide across the floor and how there is a large initial spike where it doesn't move upon colliding with the ground:

2026-04-01.16-43-04.mp4

To Reproduce

Steps to reproduce the behavior:

1. Use the Fast rapier 3D with SIMD version
2. Create a scene tree like this:

3. Enable the RigidBody3D Continuous CD option
4. Move the RigidBody3D somewhere and rotate it a bit, give it some linear velocity so that it is easy to see. See the values I set in the MRP.

Expected behavior

The rigid body should not visibly lag, stutter, or stop moving when thrown/colliding/sliding across a floor. It should remain smooth the entire time, like in the non-SIMD version of the plugin.
To see how it should look, just disable Continuous CD on the RigidBody3D inside the MRP.

Environment:

• OS: Windows 10
• Godot Version: 4.6.stable.mono
• Rapier Version: v0.8.28
• Type: Rapier Physics 3D - Fast Version with Parallel SIMD Solver

Example project(zip)

rapier-laggy-rigid-body-collision-bug.zip

[Ughuuu]

Not much to do with this one, see if any project setting changes anything, or try soft_ccd on the rigidbody. Also, open a bug in the rapier itself repo, and see if you can create a repro there as well (you would need to write rust code for that, so if that's not easy for you to do, just open a bug there and link this issue)

[Ughuuu]

This might be solved in latest version, where there was a ccd bug fixed in rapier. Try again with latest version.

[JoshuaWeissTBS]

Tried it on Rapier3D v0.8.30 SIMD, bug still happens

[Ughuuu]

As a workaround, try setting max_ccd_substeps to 2 or higher. See if it improves.
Other than that, the issue is present in rapier, and that would need a fix on their side.

[Ughuuu]

Made issue on rapier side also to track: dimforge/rapier#932

[JoshuaWeissTBS]

Tried setting max_ccd_substeps to 2 and 4 versions on SIMD 0.30 and 0.31, same issue

[Ughuuu]

Then there is no workaround for this, though the issue isn't that bad, but there is nothing that can be made on godot-rapier side to fix it.