Picking up objects issue and bug

Hi again,

I’ve got two problems:

  1. I made a blueprint for the first object (for example ball) according to this video at 2:20: Unreal 4.13 VR Tutorial - Picking up New Objects - YouTube
    When I want to make the second object’s blueprint, I cannot use anymore the two red nodes in the left side of the picture so the second object isn’t liftable.

  1. When I pick up the ball and throw, it disappears or vanishes in the ether where I cannot find it. I think it’s the bug. However, if I release it gently, it bounces on the ground or table.

Thank you for your help in advantage!

Janos Csaszar

Problem 1. In order for the two events to be available in your new object (actor), the actor’s blueprint has to implement the Pickup interface. Open the object’s Blueprint, click on Class Settings in the menu bar, then add the interface through the Details panel on the right side. After that you should be able to add the two event nodes.

It may be easier to duplicate the blueprint for the working object and just change the reference to the mesh inside it.

Problem 2. Check the mass of your ball. If a physics actor has a too small mass, when you throw it will accelerate very fast and quickly disappear in space. Increase its mass and it should solve the problem.

The first problem is SOLVED.

About the second problem, I checked it but nothing. I’ve added the physical material to the object under the Collision’s Phys Materrial Override.

The parameters of the ball:
Friction 0,7
Override Friction Combine Mode: disabled
Restitution: 0,8
Restitution Combine Mode: Max
Override Restitution Combine Mode: enabled
Density: 1,0

And the MassInKg is 1,0

When I drop the ball to the ground, it sometimes pops up unrealistically high. If I throw it away further than 2-3 metres it disappears. The ground’s Collision Presets is set to BlockAll.

What did I miss?

Did you try to increase the mass of the ball even further? How did you setup the collision mesh for the ball?

Yes, I increased the Mass Scale and MassInKg even to hundred but not really changed and the ball still disappear somehow on the ground too.

Collision parameters:
Simulation Generates Hit Events: enabled
Generate Overlap Events: enabled
Can Character Set Up On: Yes
Collision Presets: PhysicsActor
Use CCD: enabled
Can Ever Affect Navigation: enabled

In the Static Mesh Editor:
Simple Collision Physical Material: None
Collision Complexity: Project Default
Collision Presets: PhysicsActor
Customized Collision: enabled

Ok, then it is not a mass issue but very likely a collision volume issue. In the mesh editor, can you try to remove all collisions and manually add a sphere collision volume? Then use simple collisions as complex.

This problem is almost solved. Every objects work perfect with simplified collisions like capsule, sphere and box. However, I would like to add 10-DOP, 18-DOP, or 26-DOP collision for my complex objects and with these they behave oddly. Why don’t they work with these collisions? Shall I import customized collisions for complex objects?

It difficult to diagnose further without seeing your project. It could depend on your frame rate, on physics substepping or on the geometry of the collision volumes. In general simpler collision volumes have better performances. You can try to generate a custom collision volume and see if that helps. You can also add multiple simple collisions to a single mesh and arrange them in the shape of a more complex one.

I tried with several collisions for example Auto Complex Collision and customized complex collision but these are don’t work. In 3D editor software like Maya, I created the simple box around the complex mesh with UBX prefix and it works but not a more complex one. So I concluded that the issue is about the geometry of the collision volumes. In the picture the mug behaves weirdly with this collision. So what’s the ideal geometry of the collision volumes of complex meshes like mug?


What do you mean by “behaves weirdly”? Can you make at least a video for us to see? Or can you share a reduced version of your experience to show the issue?

I mean that after I drop the mug to the table or ground it pop up suddenly and fly away to anywhere where I cannot find it. With simple box collision, everything is okay and I didn’t changed the parameters.

Sounds strange to me. If you are willing to create a test project with just your mug and few other objects I am happy to look into it. I am sure either your physics materials or something else is off.