Port the physics in fixed timestep example to 3D #20089
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
janhohenheim
added
A-ECS
Jondolf
reviewed
Jul 14, 2025
Co-authored-by: Joona Aalto <[email protected]>
Co-authored-by: Joona Aalto <[email protected]>
kristoff3r
reviewed
Jul 14, 2025
Comment on lines
+342
to
+363
| #[derive(Resource, Debug, Deref, DerefMut, Default)] | ||
| pub struct DidFixedTimestepRunThisFrame(bool); | ||
|
|
||
| /// Reset the flag at the start of every frame. | ||
| fn clear_fixed_timestep_flag( | ||
| mut did_fixed_timestep_run_this_frame: ResMut<DidFixedTimestepRunThisFrame>, | ||
| ) { | ||
| did_fixed_timestep_run_this_frame.0 = false; | ||
| } | ||
|
|
||
| /// Set the flag during each fixed timestep. | ||
| fn set_fixed_time_step_flag( | ||
| mut did_fixed_timestep_run_this_frame: ResMut<DidFixedTimestepRunThisFrame>, | ||
| ) { | ||
| did_fixed_timestep_run_this_frame.0 = true; | ||
| } | ||
|
|
||
| fn did_fixed_timestep_run_this_frame( | ||
| did_fixed_timestep_run_this_frame: Res<DidFixedTimestepRunThisFrame>, | ||
| ) -> bool { | ||
| did_fixed_timestep_run_this_frame.0 | ||
| } |
There was a problem hiding this comment.
This feels like something that should be built in to bevy instead? Seems pretty widely useful.
There was a problem hiding this comment.
Agreed lol.
Can PR after this is merged.
Jondolf
approved these changes
Jul 14, 2025
kristoff3r
approved these changes
Jul 14, 2025
janhohenheim
added
S-Ready-For-Final-Review
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Objective
Since I originally wrote this example, many people on Discord have asked me specifically how to handle camera movement in and around fixed timesteps. I had to write that information up maaaany times, so I believe this is an area where the example falls short of.
Solution
Let's port the example to 3D, where we can better showcase how to handle the camera. The knowledge is trivially transferable to 2D :)
Also, we don't need to average out continuous input. Just using the last one is fine in practice. Still, we need to keep around the
AccumulatedInputresource for things like jumping.Testing
Screencast.From.2025-07-11.20-41-28.mp4
Notes