Terrain with vegetation

Hello, i try to search panda3d sample with terrain and vegetation
like this video

but only demo found is this : https://github.com/tobspr/RenderPipeline-Samples/tree/master/08-Terrain

but this demo is not like youtube video, and this demo have no forest and 3D grass

Where found sample terrain with three and grass ?
i’m started with panda3d, i have a medium experience with unity engine but i want to use open source and freedom engine,
I hesitate between panda3D and orgre 3D

My project, i want to create (easily, i want to code with hight level langage like python or lua, no opengl),
i want to create just a 3D map no game, with 3D terrain (with mountain, water, grass and three) and add road and building for simulate cars in city

*i see how create 3D terrain with multi texture (for create snow in mountain, road…)

*i see how can i load object (building tower for example) and export object to egg/bam or gz compressed with blender3D

but i have 3 problems :

  1. i don’t found any example for create three and 3D grass

  2. i found basic water sample but is there a more realistic example? water with waves?
    like this :
    water surface simulation with fshader

  3. Actualy i try to create collision detection with terrain then put my objects there without crossing the map…
    I’m currently working on the ODE or bullet physics engine, I don’t know which is the most interesting to use for my project?
    I would like my objects to detect the map and not cross it
    I would like my objects to collide with each other
    which physics engine should I use?