I need an object to not collide with only one other object, yet still collide with any other object.
Use collision groups and masks. They’re available in the physics panel. The group of the object is what group it’s in, and the mask is what groups it can collide with. Note that this is in Blender 2.5+, so grab a recent build from the buildbot or from the homepage if you can’t find it.
I am running 2.7, but I don’t understand dhow I would set this up. Can you explain in detail? I have never used the collision groups before.
Okay.
The collision groups and masks options both have 8 buttons. You can press them one at a time, or hold shift to set multiple groups.
Place the object you want to collide with everything in the same group as everything else (the default one is fine). Set the one you don’t want it to collide with in another group.
Set the first object’s mask to be all but the second object’s group. The main point is that the mask is what collision groups this object collides with, so you want it to collide with all other objects in the same group as itself, and none from the second object’s group.
It sounds more complex than it is - just set them to be in different groups, and deselect the second object’s group in the first object’s mask (i.e. the collision mask for the first object doesn’t have the second object’s group set).
If you don’t get it, just play around a bit with the settings. It should be pretty easy to pick up. Hovering your mouse over the buttons explains them well enough.
Thank you.