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‫Hello and welcome.

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‫In this lecture, we're going to be actually restricting the amount of ammo that we have so that once

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‫we have used it all up, we can no longer spawn projectiles.

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‫I've run out of projectiles and I'm even getting a message saying that I'm out of ammo, I can't spawn

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‫anymore.

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‫So let's dive in and see how we do this.

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‫So ideally what we want to happen is when our ammo goes down to zero, we are no longer able to spawn

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‫new projectiles.

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‫But how do we control the flow of our code via values in our variables?

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‫Well, the solution to this conundrum is something called the branch node.

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‫So branches, let us check if something is true or not and then do something based upon the result.

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‫So you might have a branch node that looks like this that says If I am hungry, so the condition is

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‫I'm hungry, then eat junk food while the wife isn't watching.

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‫And if that is not true, then keep playing video games.

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‫So these branch nodes allow us to do one thing in if a condition is true and another thing if it is

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‫false.

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‫Either one of these options could actually not do anything.

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‫So you could only connect up the false node, or you could only connect up the true node.

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‫Either one of these is going to work.

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‫So you'll remember that.

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‫Or you you may remember that the color red was associated with boolean type variables in unreal.

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‫So let's remind ourselves what is a bull?

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‫A bull is short for boolean and there are types that can be store one of two values either true or false,

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‫yes or no.

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‫They're often used with if statements or branches.

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‫So in the future we're going to in C++, we're going to be calling branches if statements.

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‫But it's that the same thing, same concept.

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‫And they can control whether or not something happens and certain nodes can return booleans.

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‫So what kind of nodes could return booleans?

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‫What kind of answer do we want?

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‫Well, when is it that we want to allow the spawn actor to happen?

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‫When do we want a new projectile to be created?

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‫We only want a new projectile to be created if the amount of ammo we have is greater than zero.

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‫So fortunately, if you right click in your event graph and search for greater, there is a node for

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‫that.

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‫Is these types of operators or nodes are called comparison because they take in two values and create

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‫a comparison between them and allow us to have a boolean answer.

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‫So greater is one example, less is another example.

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‫You've also can see this less equal, which means it's less than or equal.

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‫There's also equal that is it's that is one as well.

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‫Equal or not equal.

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‫If two values are the same, then return true.

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‫Otherwise return false.

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‫So let's update our glossary a little bit.

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‫We've figured out that a branch is a do something or don't based on a bull.

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‫We've figured out that bulls or booleans are a yes no data type, and that comparison is things like

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‫less than greater than equal, etc. that crucially return a boolean.

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‫So let's have a go at using one of these comparisons.

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‫I'm going to right click and add the greater comparison in here.

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‫Then I'm going to control click the ammo variable and drag it in to the first node of our comparison

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‫node.

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‫And then you can see the default here is actually greater than zero.

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‫So that's exactly what we want.

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‫We've got a node that says Is the ammo greater than zero and the return value is a boolean saying yes

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‫if it is and no if it isn't.

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‫So what we want to do is take this bool return value, drag off of that and search for branch.

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‫Then we can add in a branch node and it automatically connects up the input condition to the boolean

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‫that we were dragging.

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‫Now I'm going to drag back my space bar event and drag in its pressed node execution pin into the input

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‫for the branch.

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‫So that's going to execute our branch.

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‫Then we want the branch, if it's true, to go ahead and spawn the projectile and otherwise it's going

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‫to do nothing.

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‫So let's try this out.

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‫If we hit play and then we spawn lots of projectiles, we make our projectile value go down to zero.

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‫You can see that now, no matter how much I hit the spacebar, I'm not getting any more projectiles.

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‫So I'd like to challenge you to print out of ammo.

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‫So use the false branch so that we add a print node in there.

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‫And basically when we're out of ammo, I would like you to print out of ammo.

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‫So test your code and check that that's happening.

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‫Pause the video and have a go.

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‫Okay.

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‫Welcome back.

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‫So we've got this second branch of our branch node.

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‫Let's just drag this back so we don't get our lines crossing with these execution pins.

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‫And the false branch should come down to here where it's going to do a print string.

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‫And the string I want it to print is simply going to be out of ammo.

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‫Now, if we go ahead and play and fire off all 20 rounds of our cannonball ammo, you can see that each

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‫time I hit the spacebar, it just prints out the message that I'm out of ammo, giving the player the

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‫indication of why no more balls are spawning into the scene.

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‫That's it for this lecture.

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‫I will see you in the next one.