Gravity and Simple Collision (UE 4.27)

For now.

  • create a new actor
  • add static mesh - make sure it’s the root (drag it there)
  • enable physics simulation
  • make sure the mesh you’re using has collision (double click the mesh in the content browser)

The above is not an actor, it’s just a mesh that a component of an actor can use. This is the asset. If its collision is set up correctly, you will not even need additional collider shape.

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So, by root you mean a parent object? Because this is a puzzle demo that I have gotten help elsewhere on this forum and have had done some tinkering with, and most of the objects have BPs that give them particular behaviors when touching one another and move when pushed by the player. So, the objects are children and parent object is more of a base BP for those objects.

Also, that editor window is different from when I double-click an object from the content browser. Do I need to browse for a static mesh actor on a different kind of Content Browser?

Edit: I’ve found that menu for static mesh objects, such as the 1M Cube that is used for most objects. I can set the Collision from there; I’ll just need to look back at the screenshots. I’ll continue working on this in the morning, since it’s 3:00 AM where I live right now. Thanks for your help, so far!

No. Every actor has a root element. Since we’re inheriting from the Conductor actor, open it, drag the mesh to the root.

  • in the conductor actor

This bit is important in certain scenarios when simulating physics.

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After looking over the last few posts, here’s what I did:

  1. I made the Static Mesh the root element of each actor. Since I have a parent actor, doing this automatically changes all child actors so that their roots are also the Static Mesh itself.

  2. I have modified the 1M Cube asset by removing its default collision and replacing it with a Box Simple Collision.

  3. I have also locked all three rotation axes on the moveable actors.

  4. So far, when I push a cube off a higher platform, it will sometimes start to fall but won’t go further down until you step onto the cube. Other times, it will just float in front of the player and in midair, not going downwards at all. UPDATE: I found out why: if a cube is slightly above the ground then pushed, it will start to fall down but stop when it’s low enough for the player to step on it.

  5. I have also fixed the collision box on the RubberCube that I showed a screenshot of; now, that collision box surrounds the cube.

With all that done, what do I need to do next?

I’ve posted an update from yesterday, though I’m not sure if you noticed, since the post wasn’t made as a direct reply to your last one.

That’s it. Setting up physics sim takes 1 click and it just works - test it out in a clean project with a simple cube simulating physics and nothing else. You don’t even need additional collision shapes. See for yourself. My 1st post in this thread shows just that.


It’s impossible to tell what else you have in your project that could be causing this unheard of behaviour. :slight_smile: I, for once, have yet to hear about having to jump on something in order to make it go down (?!)

At this point you’re asking us to fix behaviour caused by something we don’t know about. What else is there in the project?


Rather than using the actors that give you grief, could you test it with a brand new, minimalistic one - does it work? At least it will narrow down where to look for the culprit.

Judging by how the previous setup was done, I would not be totally surprised if more oddities were present there. At this point, it’s a guessing game.

I could send you a copy of the project, if you want. It’s for a third-person puzzle demo I have been working on and asked questions relating to elsewhere. I do have the main mechanics done, but I wanted to see about including gravity that would involve pushing objects onto a lower floor just to try and come up with a level idea within the five-level demo.

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Sent you a PM

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