High-Speed Collision Detection Limitation

[FrostyFlame1]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When the speed of objects is significantly increased, the collision detection fails. In my case the issue begins to occur when I set the scale to around 71 pixels per meter. Despite using the bullet option and implementing raycasting, the issue persists.

Steps to reproduce

link to the game: https://gdevelop.io/game-example/free/spherez

GDevelop platform

Desktop

GDevelop version

5.3.195

Platform info

No response

Additional context

No response

[AlexandreSi]

Hi @FrostyFlame1,
Thanks for opening an issue.
I'm not surprised by this result: there is a compromise to find between a performant game and a correct simulation. And if the speed is significantly increased, this compromise might not be satisfying.
Have you seen a different result in other engines?

If you want to discuss about the values between the word "significant", I recommend you publish a game on gd.games with a control on the scale and a test case so that we can have solid grounds during the discussion.

[tristanbob]

@FrostyFlame1 I'm the one who made that Spherez template, which uses the Physics behavior (powered by Box2d)

Box2d uses continuous collision detection (CCD) for dynamic objects against static objects, so it should never miss.
The "bullet" setting also enables this CCD between other dynamic objects.

What do you mean by "collision not detected"? Are you using Physics collision or non-physics collision conditions? The non-physics condition only triggers when the objects happen to be touching during the frame (no CCD). My first guess is that you are using the wrong condition.

[FrostyFlame1]

I am using the Physics collision condition. When I changed the position of the specified event, the issue was resolved. So, the issue is not caused by the physics engine.

I deeply apologize for reporting this as a bug. and I am so grateful for your time and assistance.