These physics object wont fall straight down

Question

I'm not using any actual Animation, so I'm just trying to get my Physics objects to fall straight down. But for some reason no matter what they always just fall straight through the floor, and at an angle. I simply want them to fall down, and hit the ground and land exactly how they are, maybe some bouncing but otherwise, just straight down. But whenever I hit play they always just fall through the ground at record pace too because they will be gone by frame 2. Any ideas on how to fix this? I've tried adding collisions, messing with the mass, but it always ends up just not being anything. The plane is set to be passive so it wont move, allowing for it to be used as a floor. Otherwise, i have tried setting the physics objects to be animated, and hope that they wont fall at a circle, but that didnt work out so well. I still dont know why they are falling in a circular motion, because thats the only reason why they are falling through the ground. I even tried turning the rotation of the physics down to 0 and it changed basically nothing. It just goes in the opposite direction. I am including a dropbox file so that yall can check out the actual thing yourself so that i can get the help I need https://www.dropbox.com/s/2a46e6au8p78g3s/Crown%202.blend?dl=0 I had gotten them to fall straight once too, but insteadof the crown falling and colliding with the inside of the K and just laying on the top right portion like a hook, it landed on the top and sat there as if the K was just a flat plane too, and I dont understand it

Update: Thank you to chris i believe is the name, your answer was helpful, however with every change i made, i tried to follow your instructions to a T and it just didn't work, it just ended up having the cylinder falling and getting all jumbled up, i was hoping you might have a solution for this? I had recorded a video of it but it appears that it wont let me add it, I have added it to the drop box under the link https://www.dropbox.com/s/ulz1x3wzymxyyem/2023-06-01%2017-36-42.mkv?dl=0

Answer 1

If you are using rigid bodies, you have to understand the concept of convex hull. Convex hull means: your mesh will be simplified as if it would wrapped with plastic.

So your ground plane, which shape you did set to convex hull, will be calculated by this shape here:

And as in real world, two rigid body cannot exist "overlapping" each other without harming each other.

So this cannot work.

If you check "animated" in rigid body, this means: there will be no physics at all for this object -> you have to manually animate it.

That's why your "K" isn't moving at all.

If you change your ground to shape "mesh" and "passive" you will get this:

--- update

to let the crown fall "into" the K, i changed the K to rigid body passive, shape: mesh.

Because the crown has a ridiculous amount of vertices (over 1.7 Mio) and this takes a long time for rigid body simulation to calculate, i created a simple cylinder, gave that a rigid body and parented the crown to that cylinder. I removed rigid body for the crown itself. Then i moved the K and the crown over each other and let the rigid body simulation do its work:

and that's how the rigid body cylinder looks like: