The answer is probably “you can’t get there from here.”
Two complicated shapes (think broken glass). The edges align perfectly, which is probably the insolvable problem. Intuitively, I would expect these to drop straight down. Instead they rotate away from each other approximately along the z axis.
Blender 3.6.1
Rigid body settings: collision margin set to 0, tried both convex hull and mesh, bounciness set at 0.
Collision settings: tried a variety of settings, but didn’t expect them to do much at the start of the simulation.
Frame 1:
Frame 3:
My plan was to pre-fracture the glass, collide it with the ground, and then use Cell Fracture on some of the smaller fragments. Cell Fracture doesn’t look good at the macro level since plate glass doesn’t fracture in a Voronoi pattern.
Potential Answer #1:
Step 1: Don’t extrude the depth, leave the shapes as 2d
Step 2: Bake the simulation
Step 3: Add the depth
Problem #1:
Adding the depth later will cause shapes that land face up to extrude up, but face down shapes will extrude into the bottom collision surface. Extruding the shapes in both dimensions will minimize this. The thinner the extrusion the less noticeable it will be from a distance. Or manually tweak the end of the animation moving the shapes to rest on top of the surface.
Problem #2:
2d shapes don’t collide well. The active 2d shapes penetrate the passive surface. setting collision margin on the passive surface doesn’t seem to help. EDIT: This seems to be fixed by subdividing the surfaces a fair amount.
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Have you looked at Rigid Body Constraints?
Another thing to try… In the Rigid Body settings there is an Animate tick box. You can keyframe the tick box on/off. So you can animate the glass until one frame before it hits the ground, then turn off the animate tick box so the Rigid Body sim takes over.
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Thanks for mentioning rigid body constraints. I’m looking into that next.
Okay, lets blame this on my inexperience with physics in blender.
Why was I using Collision physics? Because Rigid body makes it rigid and collision lets them bang together, right?
Wrong!
Collision is more properly named SOFTBODY Collision.
Turn that off and my animation works how I wanted it to.
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