Introduction
Unreal Engine 5 (UE5) has introduced a multitude of advancements and features that enhance game development. However, transitioning from UE4.27 to UE5 can introduce unexpected challenges, particularly regarding physics and collision detection. One notable issue that developers have encountered is the phenomenon of actors with physics enabled passing through the floor, even when Continuous Collision Detection (CCD) is activated.
In this article, we'll delve into this problem, examine a real-world example from the Stack Overflow community, and provide insights on how to address this frustrating issue effectively.
The Problem
As highlighted by a developer on Stack Overflow, after transitioning their project from UE4.27 to UE5, they noticed that objects with physics simulation enabled would frequently fall through the floor upon being thrown. The collision was set up correctly, but the problem persisted:
"Since I've ported my project from UE4.27 to UE5 I've had this bug on every actor that has Simulate Physics enabled. I have a mechanic where the player can grab an object and then throw it to the floor. This worked perfectly on UE4.27, but on UE5 the actor will go through the floor most of the time." - Source
Understanding the Issue
Continuous Collision Detection (CCD)
Continuous Collision Detection is designed to prevent fast-moving objects from passing through other objects, particularly when frame rates are low or the timestep is not able to handle fast motions accurately. However, the introduction of new physics and collision systems in UE5 may necessitate adjustments to ensure that CCD functions as intended.
Collision Settings
In UE5, it’s essential to double-check collision settings on both the object being thrown and the floor. Mesh collision settings can sometimes differ after a port, causing unexpected behavior.
Potential Solutions
1. Review and Adjust Collision Settings
Ensure that both the physics object and the floor have the correct collision settings:
- Collision Presets: Verify that the collision settings on your physics actor are set to "Block All" or the appropriate preset.
- Collision Complexity: Consider setting the floor mesh's collision complexity to "Use Complex as Simple," which may improve collision detection accuracy.
2. Adjust Physics Settings
Increase Physics Substeps: Increasing the substeps in the physics settings can help the simulation handle fast-moving objects better. Go to the Project Settings > Physics > Subdivision Settings, and increase the substeps value.
Modify Mass and Gravity Scale: Reducing the mass or the gravity scale on objects that are causing issues might yield better results in the simulation and prevent them from falling through the floor.
3. Utilize Additional Collision Geometry
While the developer mentioned the inconvenience of adding invisible collision beneath floors, in some complex situations, it's worth exploring:
- Box Colliders: Placing box colliders strategically can help catch errant objects and prevent them from falling through floors.
- Trigger Volumes: Implement trigger volumes that can detect objects before they fall through the floor and adjust their positions accordingly.
4. Update to the Latest UE5 Version
If you have not already, ensure you are using the latest version of UE5. Developers are continuously patching bugs, and it’s possible that a hotfix addresses this collision issue.
Additional Resources
- Unreal Engine Documentation: Review the official Unreal Engine physics and collision documentation for best practices on setting up and debugging collision issues.
- Community Forums: Engaging with the UE5 community on forums like the Unreal Engine Forum or Reddit can provide insights from other developers who have faced similar challenges.
Conclusion
Transitioning from UE4.27 to UE5 can unveil various bugs and issues, particularly regarding physics and collision. While encountering problems like actors falling through the floor can be frustrating, understanding how to adjust settings, apply additional collision geometry, and utilize community resources can greatly enhance your development experience.
By following the aforementioned solutions and continuing to engage with the community, developers can work toward resolving such issues and improving the performance of their UE5 projects. Happy developing!
This article incorporates insights from the original Stack Overflow discussion, optimizing it for SEO by including keywords like "UE5", "Actors with Physics", "Collision Issues", and "Continuous Collision Detection". For more technical details, refer to the official Unreal Engine documentation linked throughout.
