Trying to fix the object

[josemendez]

Hi! Sry to bother you again...yesterday I didn't see the message

In fact, in my task, the softbody objects are actually similar to the rigidbody, that the deformation is very small. So what I want to do, is to fix the center of the mass, so that the center wouldn't move from like (0, 0, 0) to (1, 0, 0). 

Fixing the center of mass wouldn't do what you want: The center of mass is the mass-weighted average of all particles' positions, so if you fix the center of mass, moving one particle to the right would move all other particles to the left.

I think you just want to attach some particles in place, which is what attachments do.

Again take the barrel in the demo as an example. Now if we use the ball to hit it, it would fly and the surface would deform. Instead of that, I was trying to stick the barrel on the floor, like using a glue, so that when we hit it again, it would only occur deformation on the surface, and stay put. In most cases in my task, the objects are very similar to the barrels.

To achieve this, you can just use attachments. Check out the RubberDragon sample scene, as it does what you describe here: the bottom part of the dragon is attached in place using an attachment component, so that you can drag to deform it, but it doesn't move around.