It is a relaticvely known fact that physics in blender is about 1m per bu. But how important is this? In a quick study I did, I discovered that the scale in comparison to real objects isn’t important but the overal size of objects is.
First up, here’s my test blend:
physicsscale.blend (481 KB)
In it I drop cubes onto triangle meshes at a variety of scales from a 20bu cube to a 0.02bu cube. I apply a global force to make gravity be the same for each cube’s scale (so they all hit the triangle mesh at the same speed).
Summary:
- Don’t make any physics object smaller than about 0.1bu if you want stability
- Don’t make single face bigger than 20x20 bu if you don’t want flat faces to cause bumps
- All objects in blender have a 0.01 bu physics boundary around them, even if you set the margin to zero.
- Setting the margin smaller makes small objects more stable but big objects less stable
- Setting the margin bigger makes big objects more stable but small objects less stable
- The scale setting in scene properties does not effect physics at all.
Conclusions:
- If you’re going to be dealing mostly with 2cm objects, scale everything up by 10
- If you’re going to be dealing mostly with 2km objects, scale everything down by 10