How to make Two Spatial Models collision?

General Discussion
1

I am trying to make a (j3o) dragon model run on a terrain which I created by scene composer (j3o). I’ve learned the tutorial 9 hellocollision but I am not sure why it doesn’t work for my project. They dont have any collision. They submerged all the time. How do I fix my code?

    world=assetManager.loadModel("Scenes/earth.j3o");
    CollisionShape sceneShape =
            CollisionShapeFactory.createMeshShape(world);
    landscape = new RigidBodyControl(sceneShape, 0);
    world.addControl(landscape);
    rootNode.attachChild(world);
    bulletAppState.getPhysicsSpace().addAll(world);
    
    dragon = assetManager.loadModel("Models/grog5k.j3o");
    CapsuleCollisionShape capsuleShape = new CapsuleCollisionShape(1.5f, 6f, 1);
    dragon_phy = new RigidBodyControl(capsuleShape, 0f);
    dragon.addControl(dragon_phy);
    
    rootNode.attachChild(dragon);
    bulletAppState.getPhysicsSpace().addAll(dragon);
2

https://jmonkeyengine.github.io/wiki/jme3.html
https://jmonkeyengine.github.io/wiki/jme3/advanced/collision_and_intersection.html
https://jmonkeyengine.github.io/wiki/jme3.html#physics-integration

You are saying the dragon is static, like a terrain because you set the mass to 0f.

Search is in top right corner of forum,
https://hub.jmonkeyengine.org/search?q=model%20sinks

Either use an offset node or set the mesh origin and rootbone base to be at the bottom of the model.
https://jmonkeyengine.github.io/wiki/jme3/external/blender.html#model-checklist