[OpenGL] How to make terrain deformation with properties?

Sorry, I don't know about jMonkeyEngine.
However, I'd like to understand how much deformation you need.
If the system is heightmap-based, it will likely break.
Minecraft takes it easy with its grid/voxel/block-based approach: that allows easy deformation and under/overhangs. Remove that constraint and the problem becomes much more complicated. There are indeed systems supporting voxel-based editing without blockiness but I am not well aware if jMonkeyEngine supports that.

What i want is kind of like Minecraft, but without it being blocky, not sure if it's possible though, like you said.

I don't need random generation right now though, so don't worry about that.

What i was thinking was to make it like a bunch of models stuffed together like Minecraft where it's just a bunch of squares all over the place, not sure how well it would work though.

Do you have any idea on how it can be done?


PS. jMonkeyEngine is just like using LWJGL, but with an IDE to use.
So it doesn't make any difference in the code.

Make it like minecraft but with smaller voxels and smooth out the cubes based on their surroundings?

What i was thinking was to make it like a bunch of models stuffed together like Minecraft where it's just a bunch of squares all over the place, not sure how well it would work though.

Do you have any idea on how it can be done?

I had a quick glance at jME3 javadocs. I'm not 100% sure but it appears to me it only supports heightmap-based terrain. I cannot understand if it supports dynamic terrain.
My best bet would to look into "isosurface reconstruction" algorithms for voxel based structures. Asking on jME3 user forum is your best bet I suppose.

I spent quite some effort in the past in allowing multiple heightmap based terrains to be joined together like "a bunch of models". It didn't quite work out, not automatically at least... so I'm afraid I have no idea on how it can be done. For full 3D deformation, I'd go for voxels and reconstruction systems.
However, if each point can only be deformed in the sense of going up/down (not "pushed in") then heightmaps will still do. Like minecraft without blockiness? Won't do.