How to apply gravity on selected objects

[shilpesh]

Hi all,

I am new to Houdini and whole RBD system. I am facing problem with gravity force. I have copied box on the grid to create multiple boxes on the grid. Then I have assigned RBD glue object to this geometry. With Sphere applied with RBD object force I am breaking this box structure into pieces. Since the whole box structure starts falling when gravity gets activated I have put another set of boxes by making them as static object which helps holding box structure and avoids falling them on the ground. But for my scene I am creating roof top for the house using same copy method. Now the problem is since I keep entire box structure on an angle, the moment gravity gets activated whole box structure starts sliding down. I want to use gravity only for the boxes which gets hit by the sphere and rest all boxes should maintain their position. Till now I was using Group dynamic objects method where I was selecting few boxes to put them in a group. Till now I was using this method and it was kind of helping me with some cheat in the comp but still I am not satisfied with the results because after grouping few objects when sphere hits the boxes and all the boxes starts flying in the air but few boxes instead of falling on the ground starts behaving like anti gravity effect and you can see them rotating in the air but moving very slowly towards the ground.Can someone please tell me the right method to achieve the effect which I am trying to do. Please take a look at attached file which will give you better idea about the problem.

Thanks,

Shilpesh.

HowToControlGravity.hipnc