I have a complex (i.e. irregular, concave) shape obtained by photogrammetry. Now, I'd like to put it flat on a table. How to achieve this? (It ridiculously balances one point now. )

  1. Is there a smart way (method, heuristic, approach) of manipulating it using Blenders' transform tools?
  2. Can it be done using physics?

(I tried using physics. It works when I choose a 'box' for collision bounds, but when I choose 'triangle mesh', it wobbles on the table and then falls throug :D )

  • $\begingroup$ Related: blender.stackexchange.com/q/22888/599 and blender.stackexchange.com/q/5213/599 $\endgroup$ – gandalf3 Jun 18 '15 at 9:02
  • $\begingroup$ Thanks! The second link is indeed a more complicated version of my problem. The first one lacks the rotation of the object: the cilinder mentioned already has its axis paralel to the XY plane. $\endgroup$ – Ideogram Jun 18 '15 at 9:24
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    $\begingroup$ In my answer to the first question I mentioned the drop to ground addon, which takes some rotation into account. Transform snapping can also auto-rotate objects, but likely not the way you want.. You might want to try convex hull if you haven't already. Triangle mesh is pretty unstable, but you might be able to get it to work by increase the number of iterations $\endgroup$ – gandalf3 Jun 18 '15 at 9:25
  • $\begingroup$ Thanks. With help of both your comments, I fixed it. If you'd like, post them as an answer, so I can mark it as 'the' answer. $\endgroup$ – Ideogram Jun 18 '15 at 9:40
  • $\begingroup$ Looks like you beat me to it ;) $\endgroup$ – gandalf3 Jun 18 '15 at 10:16

For simple situations you can probably get away with snapping or the drop to ground addon.

For more complex situations, rigid body physics can be used:

enter image description here

You can probably use the convex hull collision shape (also see unexpected reactions in a quiet simple rigidbody physics simulation), but if you need concave collisions then you'll have to use the Mesh collision shape.

The mesh collision shape can be quite unstable, mesh to mesh collisions in particular.

One way to mitigate this is by increase the number of simulation steps in Properties > Scene > Rigid Body World:

But this doesn't always work completely. If you need to use the mesh collision shape, try to have it collide with a non-mesh shape if possible.

Also see Tips for making Mesh Rigid-body collision shapes more stable


The second comment by gandalf3 lead me to the correct answer: the Blender Game engine isn't needed anymore. I was put on the wrong track by the dominos example on the Blender wiki page (http://wiki.blender.org/index.php/Doc:2.6/Tutorials/Physics/Rigid_Bodies). Using 'enable physics' in the properties --> physics using Blender Render, I was able to drop the thing on the floor using the convex hull.

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    $\begingroup$ Yes, the wiki is old and mostly outdated. The new (still a work in progress) docs are here. $\endgroup$ – gandalf3 Jun 18 '15 at 10:16

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