In simple terms...
DOPs work differently then the SOP context.
Dops is collecting data its then trying to solve in each timestep using a... solver.
![](/static/djangobb_forum/img/smilies/smile.png)
If you look in your geometry spreadsheet when in DOPS. You will see your objects and the assigned data.
kodra
The ground plane object is not connected to RBD Solver. How does RBD Solver know its existence? Why does RBD Solver know its a collider?
If you look at the merge node. Its set to create a collision relationship between the connected objects.
kodra
And even more confusingly, they all eventually connect to a Gravity DOP. Then why the RBD Object is affected by gravity, but the ground plane isn't?
The ground plane doesnt have a solver attached to it. You will see this if you expand the objects in the geometry spreadsheet.
Each type of DOP object also got different types of data attached to it by default, wich you can see if you dive inte the rbd or ground plane nodes. You cant just plug any solver to any object, since you most probably will be missing data for the solver to work on..
So much is simplified around DOPs now adays and some of the hacks you had to do to minipulate these data tree to get what you wanted was crazy.
I think there are a few really old threads + hips from jeff wagner with examples and explanations floating around here or on odforce if you are interested.