Adding obstacles and pushing physics

While we were in the Platformer scene, let's look at one more important concept. You've probably noticed that your character isn't able to push aside the rocks. It's not that they have too much mass, it's just that Character Controllers aren't set up to be able to push things. That would require a lot more overhead. We can, however, give him a script that will give in that behavior with a lot less overhead. It finds out what direction he's going when he hit something, then it applies a physics force to the object in the same direction.

This script comes straight out of the docs when you search OnControlColliderHit. Let's go ahead and look for that. Help > scripting Reference, and we're going to search OnControllerColliderHit and enter, and we can see it says it's called when the controller hits a collider while performing a move. This is the code we're going to be using, but it doesn't have any carriage returns. So I am going to go out to the snippets file and get my version. Exercise Files12/12-04/snippets. I'll highlight them, right-click, and Copy.

Now let's tab back to the editor, create a new script, and name it Platformer_Push. In the Game Scripts, right-click > Create > Javascript Platformer_Push and Enter. We'll go ahead and open it up in the Script editor, and we can just replace what's in there and use Ctrl+V to copy in our new script. The first of var pushPower, that's going to be the force we are going to use, and then on the OnControllerColliderHit function, we're going to feed in a local variable hit, and that's the ControllerColliderHit type, and from that we're going to get the body or the rigid body of the object that was hit.

So if body equals no, that means it doesn't have a rigid body or isKinematic is checked then we're going to return. In other words, it wasn't a valid object. Otherwise, in the next section we are going to make sure that we're going to right direction, and if not we'll return, and then we need a variable for the direction, and we get that from our original local variable hit. Once we have got all that, we put it together, and body--that was the one that got hit--velocity equals the pushDir * pushPower.

Let's go ahead and save this guy and back into the editor, and we'll need to drop it on the Platform Character, and we'll be able to see it down here at the bottom. Next, we are going to need stacked crates to check out our pushPower. Let's import the CrateSmall package. Right-click > Import Package > Custom Package > 12-04 > Assets > CrateSmall, and we'll click Open and Import. Let's drag into the Hierarchy view from the Prefabs folder, here it is, and let's go ahead and focus in on it.

Double-click, and now I want to switch back to perspective view, and it seems to be missing its mesh. When this happens, sometimes you can get the mesh back by clicking on the browser and looking for the original object, Crate, and there we go. Let's make sure it's centered, so it doesn't get stuck on the wall colliders, and if I use Alt and my left mouse button it looks pretty good. And I think I want to drag mine down here about like that. And then here's what we are going to do with this guy.

He already has a Box Collider, and if we look here he already has a Rigidbody. In our Platformer level we are going to take advantage of the Rigidbody's constraints to prevent the box from going sideways. First, we are going to freeze the position X, and then we're going to freeze rotation Y and rotation Z. This will make it so our box can only roll along the platform, and it can't move sideways. I am going to spend a few moments here rearranging my power-ups. I am going to move my Key higher, and I've also got my Heart inside my lift.

So I need to get that back, and I want to put it up a little bit higher here, and then I'm going to use Ctrl+D to duplicate my crate a couple of times. Now our little character is going to have to climb up on the crates to get to the Heart. Let's click Play and test. So I am going to move him and jump him, and there we go. He fell off. So I'm going to exit Play mode, and in the Platform Asset Start I am going to turn my invisible walls back on. That should prevent him from falling off.

So now, let's do one more thing. Let's take a minute to go back and finish the DeathZone script. Now that we have objects that can be pushed off the platforms, we'll need to tell the DeathZone to destroy them. Back up in a Game Scripts folder I'm going to open the DeathZone script, double-click it, and in the script editor where I have my comment here, we're going to replace that with Destroy(victim.gameObject), and that should take care of random things like rocks and crates that fall down into the chasm.

I'll save the script and head back to the editor. We now have a very simple platformer where the player can get power ups, lose points, and push things around. Our little platformer scene is ready to become a level.