Inversed impact normal collision for very small objects with enabled ccd

Development World Creation
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1

Hi,

I found an issue with impact normal reporting from Event Hit for small object with enabled ccd.

https://www…com/watch?v=fTb77W-qv4Y

Look on debug lines, especially on floor, first impact normal is turned down almost every time.

I’m observing this issue since the beggining of development of my project > 4.2.

First of all You have to create a physically based projectile with static mesh as collider, then turn on CCD, then scale down staitcmesh’s Build scale, the scale values must give approximately collision size around 10x10x10.
Then spawn this projectile, enable collision, turn on simulation and observe the issue.

Of course turning off CCD isn’t solution here, because the projectile will fly through geometry without collision :wink:

I’ve created a sample project:

where You can reproduce this issue, the project is compatible with 4.6.1.
Just spawn player and shoot some projectiles with LMB.

Any clues how can I fix this issue? Thanks in advance.

Regards

2

Hi ,

Thank you for your report. I was able to reproduce this and have entered a bug report, UE-7093 to be assessed by the development team.

3

Rather than using physics simulation and CCD, did you try using the projectile movement component? That always performs sweeps to avoid passing through the world, and that is why we use it by default in the First Person template.