# Shield collides with own ship when going too fast

**URL:** <https://forums.unrealengine.com/t/shield-collides-with-own-ship-when-going-too-fast/228137>\
**Category:** Blueprint\
**Tags:** unreal-engine\
**Created:** [May 7, 2021, 4:16am UTC](https://forums.unrealengine.com/t/shield-collides-with-own-ship-when-going-too-fast/228137 "2021-05-07T04:16:16Z")\
**Posts on this page:** 1\
**Showing post:** 7

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**Author:** ![Everynone](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/everynone/32/1135017_2.png) [@Everynone](https://forums.unrealengine.com/u/Everynone)\
**Post date:** [May 7, 2021, 9:06am UTC](https://forums.unrealengine.com/t/shield-collides-with-own-ship-when-going-too-fast/228137/7 "2021-05-07T09:06:14Z")

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> [@WhiteRaven\_000](#):
>
> Here they explain that, when using physics, you must ignore all collisions.  
> Sounds crazy, but actually it seems that the physics engine will take care of collisions by itself.

It’s not crazy, it’s simply not true. 🙂 There’s some confusion here. You can’t have physics simulation with no collision, for example:

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/3X/d/1/d111b97d4bc939340845fb3aaf9810c31f071cf4.png)

- above, I’ve removed collision from that cube; it will never simulate physics _on its own._ That’s unless it’s attached to something that does have collision and is simulating, here - the root. That’s referred to as _welding_ in UE4.

Do note that having and using collision are 2 different things!

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/3X/a/8/a8c01a0ff9602760d94fd8456aec0a5dba233d6a.jpeg)

Simplified is used for physics sim.

* * *

In your case you had a root mesh simulating physics and an attached Shield Static Mesh that also simulates. The latter _can_ have collision but _should not_ be simulating physics separately. That’s the job of the root component to account for the welded on component:

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/3X/d/3/d3119a3da3ce3eabb3937134bf59bcccddb96865.png)

In short:

- root static mesh (yellow small box) - has collision and simulates physics  
– shield static mesh (big box) - has collision but does not sim physics

The yellow box is using its own & the blue box’s collision when simulating. This way, theoretically, those 2 entities should never interact with one another (unless overlapping ofc) but can interact with the world using their own collisions.

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