Many of us saw the Half-Life 2 videos showing off the physics engine- perhaps most notably, barrels being shot off a ledge, and bouncing down through a series of metal bars, pachinko-style. This tutorial will be updated as we learn more, but for now will give a brief outline of how to get physics "working" in your levels.
You can quickly get physical models that you can shoot around- such as barrels- into your level with the prop_physics entity. Simply load up an appropriate model, such as models/props_c17/oildrum001.mdl (they have to be compatible with this entity- if the model you have chosen does not appear in-game then you need to use a different type of prop_ entity with it!)
Now, making solids into objects which obey the laws of physics is achieved using the func_physbox entity- you don't need to use any origin brushes or the like. And that's all you need to know!
For example, we could make a see-saw, simply by placing a func_physbox on top of a solid fulcrum:
Unfortunately, you can't use this method to make a human catapault- it will think you've just been hit by a fast moving block and knock off a bit of health. You can launch prop_ and physbox entities, though!
If you give the entity prop data then you will make it destroyable. Note also that falling heavy items will cause a shudder when they hit the ground!
We could also create a platform, with barrels on top, that sits on top of a func_breakable support beam. However, to do so you must tick the "don't take physics damage" flag, otherwise the sheer weight of what's on top will break them.
Yes, you will get hurt if you stand underneath- though, sadly, the hostages won't- and I expect to see a lot of maps with traps like this in pretty soon!
Note that the prop_physics entity can also be nudged around; however, it seems that this entity is used for breakable items such as computer screens.
You can quickly get physical models that you can shoot around- such as barrels- into your level with the prop_physics entity. Simply load up an appropriate model, such as models/props_c17/oildrum001.mdl (they have to be compatible with this entity- if the model you have chosen does not appear in-game then you need to use a different type of prop_ entity with it!)
Now, making solids into objects which obey the laws of physics is achieved using the func_physbox entity- you don't need to use any origin brushes or the like. And that's all you need to know!
For example, we could make a see-saw, simply by placing a func_physbox on top of a solid fulcrum:

Unfortunately, you can't use this method to make a human catapault- it will think you've just been hit by a fast moving block and knock off a bit of health. You can launch prop_ and physbox entities, though!
If you give the entity prop data then you will make it destroyable. Note also that falling heavy items will cause a shudder when they hit the ground!
We could also create a platform, with barrels on top, that sits on top of a func_breakable support beam. However, to do so you must tick the "don't take physics damage" flag, otherwise the sheer weight of what's on top will break them.

Yes, you will get hurt if you stand underneath- though, sadly, the hostages won't- and I expect to see a lot of maps with traps like this in pretty soon!
Note that the prop_physics entity can also be nudged around; however, it seems that this entity is used for breakable items such as computer screens.