Help dealing with impact normal in unexpected direction on impact in UE4 vehicle simulation

[PhilMaguire]

Hi there,

Please could you help with some advice on how to improve/work around a collision detection normal case I am experiencing?

I have a case where 2 vehicles are hitting one another head on. The collision shapes are (deliberately) quite blocky to try and avoid too much variation in normal direction from similarly located impacts. I have also enabled CCD on the two components.

I have captured 2 pvd files to try and illustrate my problem. One is a case where I get a contact normal that I would expect from this kind of collision, which is basically horizontal, and the other is the unwanted case where the contact normal is much more downwards. I couldn't seem to upload the pvd files here so I have uploaded them to my google drive here https://drive.google.com/file/d/1ddB-jy-GvKWLCChxUM4Kt5MmNjas1aSn/view?usp=sharing

Around 80% of the time my impact normal from the initial impact is basically horizontal, which is what I would expect from a collision like this. The file "HeadOnCollision_ExpectedNormal" shows this. The impact occurs on frame 9 between component id 21322/pxshape id 21333 and component id 22608/pxshape id 22619.

Around 20% of the time my two shapes end up penetrating one another to a much greater degree and I get an impact normal that is much more downwards facing. The file "HeadOnCollision_UnwantedNormal" shows this. The impact occurs on frame 18 between component id 17547/pxshape id 17558 and component id 18746/pxshape id 18757.

Any advice would be greatly appreciated on how I could get the contact normal come back in a much more reliable, horizontal way in this case.

Thanks,

Phil