Objects in scene that should not be moving are

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:bust_in_silhouette: Asked By JimG

Wow, this is annoying. I was just about to save and publish this and it got deleted before I got to the button.

Anyways, I’m working through a 3D introduction (same as another one, but with a different name, author, etc., and easier to follow than the first). In both of these, I’ve seen a common issue that I don’t understand.

The scene (floor, StaticBody) has several inherited objects, all RigidBody. Their mesh instances all have a single convex collision sibling attached (that includes the floor).
Some of these objects however, when the floor scene is played, are moving around (only the barrels are supposed to move). One (a platform, front-left) just falls into the floor.

I’ve double-checked each one of these, and they are all RigidBody and parented to the top-level Spacial scene. Most are stable, some not so stable. I’ve also deleted and re-imported all of them, just to be sure. No change, same objects.

You can see what’s happening here.

Does anyone have any idea what might be going on here? All of the objects are from the Kenny platform kit, using the type with the .glb extension.

:bust_in_silhouette: Reply From: Coxcopi

It seems like there is something wrong with your collisions, can you show the specific scenes for the objects that are behaving weirdly?

Sure. Just one question: How do I upload an image file from my computer?

Until then, here’s what’s there (note: I’m using “>” to indent (just figured that out by accident, but it’s creating blank lines that don’t exist, so ignore those)… also, anything in is information I’m adding after confirming it:




platformClone [mesh]

CollisionShape [single convex collision sibling]

Errors in debugger (asked about in previous question, no idea what they are):

core/math/quick_hull.cpp:402 - Condition “O == __null” is true. Continuing.
core/math/quick_hull.cpp:428 - Condition “!F2” is true. Continuing.




blockslopeClone [mesh]

CollisionShape [single convex collision sibling]
Errors: same as platform




spikeslargeClone [mesh]

CollisionShape [single convex collision sibling]
Errors: same as platform




ladderClone [mesh]

CollisionShape [single convex collision sibling]

Errors: same as in platform

I’d asked about these mystery errors in a previous post. I’ve now
noticed something new about them. After opening the scene tabs above,
that get errors, I now get errors opening scenes that never had errors
before. And the most popular one is:

core/math/quick_hull.cpp:402 - Condition “O == __null” is true. Continuing.

Often, I’ll see this one error show up multiple times for some scenes. And if I didn’t already mention this, I’m clearing the error messages each time before opening another scene to make sure the errors I see are for that scene (or at least, I THINK that’s how it works).


JimG | 2020-08-01 13:54

So you have the collision shapes and the meshes in the scene, and then add the scenes as children of RigidBodys?

Coxcopi | 2020-08-01 14:26

Here’s the exact process:

I start in Scene, making sure the top-level Spatial (which everything else is a child of) is selected. Then, I double-clicking on the sprite I want to import (all .glb). Then click on New Inherited, make sure it’s set to RigidBody in the Import tab and, if necessary, set it to RigidBody and re-import. Then, back in Scene, I make sure it’s RigidBody (I discovered that sometimes, no matter how you import it, it still wants to be a static body) and change its type if it isn’t. I click on the Clone (mesh), and in the Mesh tab, I add a single convex collision sibling.
Then I save the scene.

After that, I click on floor, then the chain link and instance the above new scene into the floor scene.

Most of the time, that works just fine. But for a few, well, they like to move around on their own. Now, in the previous (scrapped after I gave up with this, certain that I’d done something horribly wrong, one of those was the spikessmall … and this time, it’s spikeslarge. Could it be something in the sprites themselves? It does only seem to happen with specific ones.

I think I mentioned this, but these are all from the Kenney Platform Kit, using the GLTF format.

JimG | 2020-08-01 18:02

Sorry if I don’t understand but what do you mean by Sprites? Sprites are referred to as 2D Canvases. Also, how exactly do you set up the RigidBody, can you upload another video or something. I’m really trying to help you, but I don’t quite understand your workflow, so any video or picture (you need to upload pictures somewhere else and send a link btw) are really helpful.

Coxcopi | 2020-08-01 18:44