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In this lecture, we're going to take a closer look at how to manipulate physics in Roblox Studio by

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manipulating the assembly linear velocity property of parts, as well as using a couple constraints.

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One is called vector force and the other is called linear velocity.

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Before we get started, we should first differentiate between these three things and when you would

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want to use them.

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If you need to apply a one time initial force on an object, then this is where you would use the assembly

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linear velocity property or use a function on base parts called apply impulse to apply a one time force

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onto your object.

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This of course, will take into account the different properties for your objects, such as the mass

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of the object and any type of friction acting upon your object.

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And if you need to apply a constant force instead of a one time force on your object, then instead

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you would use something called a vector force instance, which will constantly apply a force over and

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over on your object.

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And since this constantly applies a force, these forces can build up over time, which could result

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in very high speeds on your object if you don't have any other forces acting on it.

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And then lastly, if you need to have a constant velocity on your object instead of a constant force,

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then you would use a linear velocity instance, and this will have your part constantly move at a consistent

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velocity, regardless of its mass or its size.

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So let's go ahead and first take a look at assembly linear velocity and using a function called apply

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impulse on parts.

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Every single part in your game is going to have an assembly linear velocity.

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And they're also going to have a function to apply an impulse on that part.

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Now we can set the assembly linear velocity of a part directly through the property menu.

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So no matter what the mass of our object is, if we were to update the value of the assembly linear

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velocity to ten, then that's going to be the force applied.

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So my mass is currently at 44.8.

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And then if I hit enter here, as you can see my part jumped a little bit.

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But if I were to decrease the mass, let me enable custom physical properties and set the density all

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the way to 0.01.

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I'm going to have a very tiny little mass, and you would think that me applying this same force would

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mean that my part would jump up higher.

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But you're going to be wrong.

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It still only jumps the same amount, and that's because we're keeping the assembly linear velocity

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the same.

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The previous one had an assembly linear velocity of ten or positive ten force in the y axis.

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And so also was the force that we applied on this part with a smaller mass.

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So the assembly linear velocity is a property that represents the movement of our part in how many studs

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per second.

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So basically you could think of me applying a force of ten means my part would move ten studs per second

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positive in the y axis.

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Now of course, we didn't move ten studs because our part still has a mass to it.

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And this was also a one time force that was also being pulled back down by gravity.

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But if we were to imagine that there was no gravity in the game, there was no friction and I were to

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set the assembly linear velocity to ten, my part would be moving ten studs per second in the y axis

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or in the positive y direction, because this value actually represents the direction of the force based

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on the global axes.

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So if I were to apply a positive force on the y axis, it's always going to be up.

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It doesn't matter what the orientation of the part is.

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Now, setting the assembly linear velocity directly may result in unwanted behavior, because maybe

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you want parts that have more mass to move less, while you want to have parts that have little mass

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to move more.

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Well, if you were to set the assembly linear velocity and always set it to the same value of, let's

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say ten in the positive y axis, no matter what the mass of the part is, it's always going to move

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the same amount.

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So in order to solve that, we can use a function called apply impulse to apply a force on our object.

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And that will take into consideration the mass and let's say the friction, uh, that is being applied

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on our object.

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So I'll make a reference to my physics part in the workspace.

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And I can apply an impulse.

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And my impulse is going to be a vector 3.nu.

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And we'll do let's say a value of ten on the y axis.

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Now let me increase the density back to 0.7 so we can get our mass of 44.8.

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And if I hit enter, what you're going to notice is that my part didn't move at all, because this was

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a very small force that just couldn't stand up against this mass.

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It basically didn't move my part at all.

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Now, if I were to reduce the density all the way down to 0.01, we should see our part move a little

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bit.

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So if I hit enter, there we go.

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Our part bounced up just a little bit because.

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It's basically almost massless.

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If I bring the density back to point seven and I apply a greater impulse, let's say an impulse of 500,

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then now my part bounces a little bit.

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But if I were to swap the density back to 0.01 and apply this impulse, you're going to see that my

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part just shot straight up into the air, because it's basically massless.

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And we applied a huge force onto that part.

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So this function is great for when you need to just apply a one time force on an object in a particular

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direction.

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And if you need to take into account the mass of your object, if you want to be able to set the linear

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velocity directly without having to worry about the mass of the object, maybe you always want it to

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move in the same direction, the same amount.

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Then you would set the assembly linear velocity property directly.

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Now there's another property here called assembly angular velocity, which is basically the exact same

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thing as the linear velocity.

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But instead this is representing rotational velocity.

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So if I want my part to apply a rotational force, let's say a positive rotational force around the

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y axis, if I were to do like 100.

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As you can see, my part spun a lot and then eventually that force went back down to zero due to friction.

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I can also take into account the mass of the object when I'm applying a rotational force.

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By using the apply.

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I believe it is.

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Is it angular?

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Yeah.

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Apply angular impulse property.

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So if I need to apply a rotational force on my object, and I want to keep it consistent across multiple

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different objects with different masses, you can set the property directly.

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Otherwise, if you need to take into account the mass of your object, then you would want to use the

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apply angular impulse function.

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So I could apply an angular impulse here.

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Let's say uh a value of ten on the x axis.

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And if I were to do this it only moves a little bit because, um, we're basically fighting against

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this jagged object.

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It's not going to be very easy to rotate it.

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So let me try maybe a value of 100.

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Okay.

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There we go.

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We got it to flip.

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And then if I were to increase the density to like a value of one, make it really heavy and then apply

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this force.

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As you can see it does absolutely nothing because this object is too heavy to rotate with this current

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force that I'm applying.

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But if I bump that up and make it a big value now, I'm able to actually spin my object.

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And if I have that density, go back down to 0.01 and then apply this force.

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My part is gone, because that was just way too much force to apply on such a light object.

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All right, the next thing we're going to go ahead and take a look at is going to be a vector force,

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which applies a constant force on an assembly.

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So I need to add an attachment into my part.

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This is going to be where the force is being applied.

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And then I can go ahead and add a vector force.

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And then I need to define what attachment I need to apply a force at.

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Let me go ahead and actually set the force to zero first of all.

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So that way it's not going to apply a force right away.

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But now I have defined this vector force as applying a force at this attachment.

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And currently it's going to apply a force relative to the orientation of my attachment.

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So this force vector right here is going to be dependent on what way my attachment is facing.

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If I want to instead have this force be applied based on the global axes of the world, then I can just

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switch this relative to property to world.

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And then let me go ahead and try to apply a force of, let's say, ten on the y axis.

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If I do that, you're going to see my arrow appear and it's trying to apply a force of ten on the y

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axis, and it's constantly applying this force.

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But of course, because my object is too heavy, nothing is happening.

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But if I decide to bump up this value a bit more, maybe to 100.

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Nothing's going to happen yet.

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Maybe I'll try a thousand.

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Still nothing.

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How about about 10,000?

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Okay, there we go.

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And now my object is starting to fly away.

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And let me bring that value back down.

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And eventually I had to get to a point where my force went beyond the force of gravity.

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I think the force of gravity.

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What is it?

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Where can I find.

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Okay, gravity is 196.2, so I should be able to overcome gravity when this force here goes beyond that.

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So if I set this to 192 or 193.

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That actually still might not be enough because my object is too heavy.

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So let me try reducing the density.

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Okay.

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Yeah, there it goes.

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A little bit too much force.

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Let me bring that back down to zero.

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Come back.

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But what you should be noticing is that as I am applying this constant force to my objects, it is getting

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faster and faster and faster because there's nothing stopping it.

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It's constantly applying a force and that force is building upon each other.

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All right.

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So considering that the amount of force that we need to overcome gravity with is going to be equal to

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the mass of the object multiplied by the gravity in our game, uh, we should take into account our

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mass, which is 0.64.

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And we should multiply that by our gravity, which should give us a value that perfectly counteracts

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gravity.

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Which means if I were to move this part upwards, it should float in the air because it's fighting against

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gravity perfectly.

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So 196.2, which is the gravity in the game multiplied by 0.64, which is the mass of our object, will

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yield us a value of 125.568, which should be the force required to not have this object fly away,

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but be basically still wherever we put it, because it's perfectly balancing out against gravity.

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So if we set this to 125.568.

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As you can see, nothing is happening.

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But as soon as I lift my object up.

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Look at that.

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Our part is unanchored, but it's floating.

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And that's because this vector force is constantly applying a force that's perfectly counteracting gravity,

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which means I could take another part like this and I could knock it into my object.

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Let me see if I can change this.

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Maybe to no, I can't change it to physical.

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How could I, how could I knock this object into the other object here if I put.

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Okay, there we go.

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That kind of worked.

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So as you can see now, our object is basically acting like there's no gravity in the game because I

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can knock it around and it doesn't matter because this force inside of it is constantly working against

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gravity.

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This is basically now zero gravity, so any outside force I apply on it, it's going to completely disregard

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gravity, which is really, really cool.

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Now you keep hearing me use the terms assembly when we're talking about these different properties of

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applying mass.

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So let's go ahead and learn what an assembly is.

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And I think the best way to learn what an assembly is, is by actually going to the official Roblox

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documentation and reading what they have to say.

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So inside of the Roblox documentation, they state that an assembly is one or more parts welded by a

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rigid well constraint, or connected through movable joints like motor six DS.

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You can group an assembly of parts in a model container to quickly organize the parts and related objects

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as a single asset.

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So basically, an assembly is just a bunch of parts that are connected together through welds or other

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types of joints that basically act as one big body of objects.

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And because you have the possibility of multiple parts being welded to other parts, you also have to

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take into account the mass of those other objects as well when you're calculating physics.

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So it says from a physics perspective, an assembly is considered a single rigid body, meaning no force

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can push or pull the connected parts from each other, and they will move as a single unit.

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All forces applied to a specific base part are applied to its assembly.

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For instance, base part.

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The apply impulse function applies impulse to the assembly at its assembly center of mass.

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So if you had one single part not welded to anything else, then the center of mass would obviously

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be within the center of the part.

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But if you had maybe two parts that were, let's say, ten studs away from each other, welded to each

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other, then the center of mass would obviously be within that distance between those two separate parts.

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The Roblox documentation states that every assembly has a root part indicated by its assembly root part

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property.

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This is the part that doesn't move when the motor 60 transforms are updated, as well as the part used

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to keep consistent physic replication and network ownership.

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You cannot explicitly set the root part, but the following factors affect probability from highest

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to lowest.

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So the Roblox game engine automatically picks what the root part of an assembly is going to be, and

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it does it in this order.

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An anchor part will always be assigned as the root part, which makes sense.

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Parts with massless set to false take precedent.

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Higher root priority values take precedent, and then finally precedence based on the part size with

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multipliers for parts with specific names.

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So basically parts that have higher masses are going to likely be the parts set as the root part of

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the assembly.

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Back inside of studio.

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If we currently look at the assembly section, you will see the assembly center of mass, which is going

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to be the central position of my object, which is why this value also matches the position of my object

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and also matches the origin of my object.

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And then it also gives the assembly root part.

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Now, since this is only one single part, obviously the assembly root part is the part itself.

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But let's say I were to duplicate this part.

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And I were to call this my physics part number two.

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And let's say I made this one super heavy.

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Let's increase the density to like ten.

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So now I have a mass of 640.

230
00:15:11,790 --> 00:15:15,060
And then let's go ahead and weld.

231
00:15:16,240 --> 00:15:18,490
This part to my other part.

232
00:15:18,490 --> 00:15:21,610
And now this is my assembly of two parts.

233
00:15:21,610 --> 00:15:27,040
And if you take a look at my second part and we were to look at the assembly route part, obviously

234
00:15:27,040 --> 00:15:32,410
now the new assembly route part is going to be my second physics part, because it is much heavier.

235
00:15:32,410 --> 00:15:38,470
And you can also see the total mass of the entire assembly, which includes the mass of this part and

236
00:15:38,470 --> 00:15:40,480
the mass of this part added together.

237
00:15:40,900 --> 00:15:46,630
Now, if I were to add an attachment inside of my first physics part, and then let's say I added another

238
00:15:46,630 --> 00:15:52,030
vector force, and I wanted to start applying forces relative to the world.

239
00:15:52,030 --> 00:15:54,490
And let's go ahead and assign it this attachment.

240
00:15:55,600 --> 00:15:58,930
As you can see, nothing is happening.

241
00:15:58,930 --> 00:16:04,240
And that's because the amount of force I'm applying is not enough to overcome the amount of friction

242
00:16:04,240 --> 00:16:06,850
with the ground due to the weight of this assembly.

243
00:16:06,850 --> 00:16:08,740
So let's actually bump this up a bit more.

244
00:16:08,740 --> 00:16:09,940
How about 10,000?

245
00:16:10,560 --> 00:16:11,190
No.

246
00:16:11,190 --> 00:16:12,300
Doesn't want to work.

247
00:16:12,300 --> 00:16:13,470
Is it still too heavy?

248
00:16:13,470 --> 00:16:16,980
Okay, then how about we do a hundred thousand?

249
00:16:18,660 --> 00:16:19,830
Okay, there we go.

250
00:16:20,040 --> 00:16:20,730
Oh, no.

251
00:16:20,730 --> 00:16:21,510
Come back.

252
00:16:21,510 --> 00:16:21,990
All right.

253
00:16:21,990 --> 00:16:23,790
That was obviously way too much force.

254
00:16:23,790 --> 00:16:26,460
And it was going in that direction we defined in the world.

255
00:16:26,460 --> 00:16:30,480
So let's actually let's swap this relative to the attachment.

256
00:16:30,480 --> 00:16:35,130
So that way when it starts applying the force um, once the force becomes greater enough, this should

257
00:16:35,130 --> 00:16:40,350
start spinning in a circle because it's no longer going to apply the force based on the axes of the

258
00:16:40,350 --> 00:16:40,980
world.

259
00:16:40,980 --> 00:16:44,220
So let's actually try increasing okay.

260
00:16:44,220 --> 00:16:44,910
There we go.

261
00:16:44,910 --> 00:16:48,480
See, now my part is spinning, uh, faster and faster.

262
00:16:48,480 --> 00:16:49,230
I'm.

263
00:16:49,320 --> 00:16:50,670
This is not good.

264
00:16:50,670 --> 00:16:53,190
Let me let me decrease that force.

265
00:16:53,190 --> 00:16:54,060
Okay, there we go.

266
00:16:54,060 --> 00:16:55,350
It's slowed down.

267
00:16:55,620 --> 00:17:00,510
But as you can see, it started spinning in a circle because we're applying the force relative to the

268
00:17:00,510 --> 00:17:01,290
attachment.

269
00:17:01,290 --> 00:17:04,800
And that's going to be based on the orientation of our attachment.

270
00:17:04,800 --> 00:17:10,530
So as we're applying a force our part is obviously going to start rotating because this one's lighter

271
00:17:10,530 --> 00:17:11,520
and this is the heavier part.

272
00:17:11,520 --> 00:17:13,590
It's going to rotate around this part.

273
00:17:13,590 --> 00:17:19,800
And it's going to keep building up force and more force and more force until eventually it spins so

274
00:17:19,800 --> 00:17:24,060
fast that it'll probably let's actually see how fast we can get it to spin.

275
00:17:24,940 --> 00:17:31,540
So this is applying constant force and it's going to get faster and faster and faster until eventually

276
00:17:31,540 --> 00:17:35,890
we might make some kind of particle accelerator or a nuclear bomb or something.

277
00:17:35,890 --> 00:17:39,640
I don't know, but it's going to keep getting faster and faster, faster.

278
00:17:41,500 --> 00:17:43,840
Um, let's actually make it really fast.

279
00:17:43,840 --> 00:17:45,460
Let's apply more force.

280
00:17:47,370 --> 00:17:48,900
How about more force?

281
00:17:50,860 --> 00:17:56,830
And eventually, at this point, we'll get to, uh, a point of no return and we might break the physics

282
00:17:56,830 --> 00:17:57,580
engine.

283
00:17:57,580 --> 00:17:59,860
Hopefully this thing will calm down.

284
00:18:02,210 --> 00:18:04,490
But I don't think it wants to come down.

285
00:18:04,520 --> 00:18:05,330
Uh oh.

286
00:18:06,050 --> 00:18:11,000
But we should basically be noticing is that, of course, it's applying the force relative to the attachment.

287
00:18:11,000 --> 00:18:16,760
And since our second part over here is the bigger, heavier and badder part out of this assembly, that

288
00:18:16,760 --> 00:18:22,550
force is being applied, uh, basically, uh, currently where the attachment is now, we can actually

289
00:18:22,550 --> 00:18:26,690
change where this force is going to be applied if we tick apply at center of mass.

290
00:18:26,690 --> 00:18:32,510
So instead of applying the force at where this attachment is and to demonstrate that, let's move this

291
00:18:32,510 --> 00:18:38,330
detachment way far out like over there because we have apply at center of mass enabled, it's going

292
00:18:38,330 --> 00:18:42,770
to apply the force wherever the center of mass is for this assembly.

293
00:18:42,770 --> 00:18:49,370
And that means if we were to increase the value to like 25,000, actually that's not great enough.

294
00:18:49,370 --> 00:18:51,020
Let's try 30,000.

295
00:18:51,350 --> 00:18:51,890
Nope.

296
00:18:51,890 --> 00:18:53,270
How about 40,000?

297
00:18:54,350 --> 00:18:55,130
50,000.

298
00:18:55,130 --> 00:18:56,000
Okay, there we go.

299
00:18:56,000 --> 00:19:02,450
As you can see, it's no longer going to rotate because it's applying the force at the center of mass

300
00:19:02,450 --> 00:19:03,710
of this assembly.

301
00:19:03,740 --> 00:19:04,670
Pretty cool.

302
00:19:04,910 --> 00:19:10,790
So definitely one of the very useful features of a vector force is because it applies a constant force.

303
00:19:10,790 --> 00:19:17,090
You can manipulate gravity for individual players without having to manipulate the gravity for the entire

304
00:19:17,090 --> 00:19:19,550
workspace or other physics in your game.

305
00:19:19,550 --> 00:19:24,650
For example, if I want to have my player to have reduced gravity and only this particular player,

306
00:19:24,650 --> 00:19:30,830
I can add a vector force to their root part and assign it to some kind of attachment that I've placed

307
00:19:30,830 --> 00:19:32,780
at the center of the root part.

308
00:19:32,780 --> 00:19:37,610
And then I have applied a force or a constant force of 2000 relative to the world.

309
00:19:37,610 --> 00:19:40,610
So it's going to be always upwards that force.

310
00:19:40,610 --> 00:19:47,840
And now when I go and jump, as you can see, it's acting like I'm in a place that has very low gravity.

311
00:19:48,920 --> 00:19:53,990
And then, of course, if I wanted to have zero gravity in the game, then I would need to simply refer

312
00:19:53,990 --> 00:20:01,970
to the total assembly mass and then multiply that according to the gravity in the game, and then set

313
00:20:01,970 --> 00:20:07,550
that value inside of the vector force to basically have no gravity for my player.

314
00:20:08,450 --> 00:20:13,280
The last instance that we're going to take a look at here is going to be the linear velocity, which

315
00:20:13,310 --> 00:20:17,660
applies a constant velocity on an object regardless of its mass.

316
00:20:17,690 --> 00:20:25,160
So instead of needing to apply a constant force, if you need to apply a constant velocity and you want

317
00:20:25,160 --> 00:20:31,010
an assembly to always move at the same constant speed, then this is going to be a useful constraint

318
00:20:31,010 --> 00:20:31,490
for that.

319
00:20:31,490 --> 00:20:35,210
So let me add an attachment into my physics part.

320
00:20:35,780 --> 00:20:37,550
Let me set the attachment.

321
00:20:38,450 --> 00:20:40,040
Right there and then.

322
00:20:40,040 --> 00:20:43,550
Now I can go ahead and define a vector velocity here.

323
00:20:43,550 --> 00:20:45,650
Currently it's set relative to the world.

324
00:20:46,040 --> 00:20:53,420
And then maybe I want my part to always move one stud every single second in the x direction.

325
00:20:53,420 --> 00:20:55,220
So if I apply that force.

326
00:20:55,880 --> 00:20:59,870
Currently nothing is working because there is force limits enabled.

327
00:20:59,870 --> 00:21:05,000
But if I disable that, as you can see, it's going to start moving my object in that direction.

328
00:21:05,000 --> 00:21:08,930
It doesn't care about any physics or anything because we don't have force limits enabled.

329
00:21:08,930 --> 00:21:12,920
And now my object is always going to move one stud every single second.

330
00:21:12,920 --> 00:21:18,170
And of course I can increase the speed to two studs, and then I can increase it to three studs.

331
00:21:18,170 --> 00:21:24,080
And it's going to always constantly apply that force to try and move that direction that we have defined,

332
00:21:24,080 --> 00:21:24,920
which is positive.

333
00:21:24,950 --> 00:21:27,410
Two in the X direction.

334
00:21:27,410 --> 00:21:34,340
And as you can see, it even lifted up the entire mass just to just to go in that particular direction.

335
00:21:34,730 --> 00:21:40,880
Now, an interesting thing about this constraint is if I were to set the vector velocity to zero, and

336
00:21:40,880 --> 00:21:47,240
I have this enabled with no force limits, you can basically now think of this part as anchor.

337
00:21:47,240 --> 00:21:53,150
You can't move it because I've explicitly defined the velocity for this object to always be zero.

338
00:21:53,150 --> 00:21:56,990
So that means even if I were to raise it into the air.

339
00:21:57,520 --> 00:22:01,810
I think I broke the well, actually, no, it's still working.

340
00:22:02,970 --> 00:22:08,730
If you notice, my object is not, uh, actually, it is moving.

341
00:22:09,060 --> 00:22:10,800
It is very slowly moving.

342
00:22:10,800 --> 00:22:12,810
Let me let me move it up a little bit more.

343
00:22:13,970 --> 00:22:17,300
So if I were to do that and then let's say I did that.

344
00:22:21,460 --> 00:22:27,220
Okay, you can basically see that my object is stuck in the air because I've explicitly defined the

345
00:22:27,220 --> 00:22:28,900
vector velocity to be zero.

346
00:22:28,900 --> 00:22:31,330
Now that doesn't affect the angular velocity.

347
00:22:31,330 --> 00:22:36,070
As you can see, it's still kind of rotating around, uh, the point at which this vector velocity is

348
00:22:36,070 --> 00:22:37,060
being applied.

349
00:22:37,060 --> 00:22:42,250
But since I want the vector velocity to be zero, my part is basically now stuck in the air, even though

350
00:22:42,250 --> 00:22:43,270
it's unanchored.

351
00:22:43,270 --> 00:22:45,010
And then maybe I could be like, okay, you know what?

352
00:22:45,010 --> 00:22:51,400
I want to apply a constant velocity upwards, or I want to have a constant velocity and on my object

353
00:22:51,400 --> 00:22:58,150
will always move positive one studs upwards every single second, regardless of even if I change the

354
00:22:58,150 --> 00:22:59,350
mass of this object.

355
00:22:59,350 --> 00:23:04,300
So if I want to make this even heavier, as you can see, it doesn't do anything, it's still moving

356
00:23:04,300 --> 00:23:06,700
at that same velocity if I.

357
00:23:06,850 --> 00:23:07,210
All right.

358
00:23:07,210 --> 00:23:08,500
Actually, I think that's the limit.

359
00:23:08,500 --> 00:23:09,610
Can I make it any higher.

360
00:23:09,610 --> 00:23:09,850
No.

361
00:23:09,850 --> 00:23:10,480
Okay.

362
00:23:10,480 --> 00:23:17,500
So even though the density of my object is 100 and the mass is 6400, it's still moving up at the same

363
00:23:17,500 --> 00:23:18,010
speed.

364
00:23:18,010 --> 00:23:22,000
And even if I were to set the density all the way to 0.01.

365
00:23:22,740 --> 00:23:27,840
Still nothing happens because it is applying a constant force.

366
00:23:27,840 --> 00:23:31,260
It doesn't care about the mass or friction in the game.

367
00:23:31,680 --> 00:23:36,540
There is one last thing I would like to go over in this lecture, which is network ownership.

368
00:23:36,570 --> 00:23:42,630
There were some additional properties that I did not go over in those other constraints.

369
00:23:42,630 --> 00:23:47,190
If you want to learn more about them, there will be articles linked to this lecture that you can go

370
00:23:47,190 --> 00:23:51,660
ahead and take a look at and mess around with those constraint instances a little bit more.

371
00:23:51,660 --> 00:23:55,890
But on the topic of network ownership, I think this is very important to understand.

372
00:23:55,890 --> 00:24:02,370
And network ownership is basically this idea that something has to calculate the physics for unanchored

373
00:24:02,370 --> 00:24:03,000
parts.

374
00:24:03,000 --> 00:24:08,010
Because these two parts are unanchored, they're going to have physics such as gravity and the like

375
00:24:08,010 --> 00:24:08,910
acting upon it.

376
00:24:08,910 --> 00:24:15,540
And in order for the game or the server that is hosting the game to save resources, it will outsource

377
00:24:15,540 --> 00:24:20,970
that computation to any players that are nearby to unanchored parts.

378
00:24:20,970 --> 00:24:26,340
So what I'm going to do is I'm going to launch a one player server and show you exactly how this network

379
00:24:26,340 --> 00:24:27,510
ownership works.

380
00:24:27,630 --> 00:24:30,480
So here I have my view on the client.

381
00:24:30,480 --> 00:24:33,600
And then here I have my view on the server.

382
00:24:33,600 --> 00:24:40,080
And right now by default, because these two unanchored parts are close to my player, my player has

383
00:24:40,080 --> 00:24:47,460
automatically gained network ownership over them, which means my computer is handling the physics calculation

384
00:24:47,460 --> 00:24:51,150
for these parts, and I can replicate that information to the server.

385
00:24:51,150 --> 00:24:55,020
And the server replicates that information back to all the other clients in the game.

386
00:24:55,020 --> 00:25:00,300
Now, this means that if I were to try to move these parts, actually they might be a little bit too

387
00:25:00,300 --> 00:25:01,800
heavy for me to move.

388
00:25:01,800 --> 00:25:05,880
Let me reduce the mass for these objects, okay?

389
00:25:05,880 --> 00:25:08,490
I've reduced the mass for this particular assembly.

390
00:25:08,490 --> 00:25:14,310
And as you can see as I move this object, I'm actually calculating the physics for that on my, uh,

391
00:25:14,310 --> 00:25:20,010
my computer, which is why me interacting with this particular assembly is actually really smooth.

392
00:25:20,040 --> 00:25:23,880
It's because I'm handling the physics and I'm giving that information to the server.

393
00:25:24,030 --> 00:25:29,010
And in the server view, the server also gets to see that I am moving these objects around.

394
00:25:29,850 --> 00:25:36,060
Now, an issue with network ownership or a vulnerability is because I have control over the physics

395
00:25:36,060 --> 00:25:37,590
of this part on my client.

396
00:25:37,590 --> 00:25:44,910
That means there is really nothing stopping me from manipulating the position or the forces being acted

397
00:25:44,910 --> 00:25:46,650
on these parts.

398
00:25:46,920 --> 00:25:51,000
So as an example, what I'm going to do is I'm going to open up the explorer window.

399
00:25:52,040 --> 00:25:55,520
And let me go ahead and select, let's say this part here.

400
00:25:55,520 --> 00:25:57,800
And let me just start moving it with the move tool.

401
00:25:59,890 --> 00:26:01,480
Actually, it's not working, is it?

402
00:26:01,480 --> 00:26:03,190
Because it might be because they're welded.

403
00:26:05,530 --> 00:26:10,360
Okay, so it's a little broken on my client side, but I am moving.

404
00:26:10,360 --> 00:26:14,110
I believe this should be the, uh, part that has.

405
00:26:14,110 --> 00:26:14,440
Okay.

406
00:26:14,440 --> 00:26:14,770
Yeah.

407
00:26:14,770 --> 00:26:19,870
So because this is the, I guess, root part for this assembly, that's why I'm moving.

408
00:26:19,870 --> 00:26:24,340
The other part wasn't working because this is not the root part for the assembly.

409
00:26:24,340 --> 00:26:25,420
This is.

410
00:26:25,420 --> 00:26:32,080
But as I start moving it, what you'll notice is that the server is also seeing those changes of me

411
00:26:32,080 --> 00:26:33,010
moving this part.

412
00:26:33,010 --> 00:26:39,490
I have control over where this part is positioned, or I even have control over the rotation for this

413
00:26:39,490 --> 00:26:40,090
part as well.

414
00:26:40,090 --> 00:26:44,980
So if I start rotating it, you're going to notice that those changes also replicate to the server.

415
00:26:44,980 --> 00:26:48,220
And that's because I have network ownership over this part.

416
00:26:48,550 --> 00:26:54,010
If I want to be able to manually set the network ownership of a part, that's easy to do, there's a

417
00:26:54,010 --> 00:26:55,000
function for that.

418
00:26:55,510 --> 00:27:01,810
So what I'm going to do is in the workspace, I'm going to get my physics part number two, and there's

419
00:27:01,810 --> 00:27:03,760
a function called set network owner.

420
00:27:04,180 --> 00:27:11,860
And to have the network ownership be given to the server and the server alone, I need to pass nothing

421
00:27:11,860 --> 00:27:12,880
or basically nil.

422
00:27:12,880 --> 00:27:14,890
And once I do that and I hit enter.

423
00:27:14,890 --> 00:27:19,810
Now the physics for this part is going to be handled by the server and not my client, which means,

424
00:27:19,870 --> 00:27:24,850
as you can see, I'm no longer able to rotate it and replicate those changes to the server, even if

425
00:27:24,850 --> 00:27:27,280
I were to move this part around.

426
00:27:27,280 --> 00:27:29,890
So let me pull out the move tool and start moving it.

427
00:27:29,890 --> 00:27:32,290
And as you can see, this is not working.

428
00:27:32,290 --> 00:27:37,750
It's being weird on my client, but you can see that the position is not updating on the server at all.

429
00:27:38,690 --> 00:27:44,900
And it's also going to be a little bit wacky because as I move this object, I mean, obviously it's

430
00:27:44,900 --> 00:27:52,190
bugged on my view, but you'll notice that this the physics for this part is not exactly responsive.

431
00:27:52,190 --> 00:27:55,400
And that's because I'm not calculating the physics for it on the client.

432
00:27:55,400 --> 00:28:00,740
The server is so it's being a little bit unresponsive and it's being a little bit slow.

433
00:28:00,740 --> 00:28:02,360
And this kind of sucks.

434
00:28:02,360 --> 00:28:09,860
So this is also the reason as to why even our character models, uh, we have a network ownership over

435
00:28:09,860 --> 00:28:11,870
them, which is why they're really responsive.

436
00:28:11,870 --> 00:28:17,150
If I move them around, I'm actually calculating all the physics for my character model on my client

437
00:28:17,150 --> 00:28:22,400
side, and I'm replicating that information to the server, which means if I were to actually refer

438
00:28:22,400 --> 00:28:23,900
to my character model.

439
00:28:23,900 --> 00:28:29,930
So this is player one and I were to get the character or actually the humanoid root part, I believe.

440
00:28:29,930 --> 00:28:30,080
Yeah.

441
00:28:30,080 --> 00:28:34,640
Let me get the humanoid root part and let me set the network owner to the server.

442
00:28:34,640 --> 00:28:40,040
Once I do that, I have lost control over the physics calculation for my character.

443
00:28:40,040 --> 00:28:46,070
And as I start, oh gosh, it is extremely delayed and unresponsive.

444
00:28:46,070 --> 00:28:52,580
So right now I'm pressing W and it took about a second for it to respond to my input.

445
00:28:53,240 --> 00:28:57,680
And if I were to press spacebar, as you can see, it's really slow.

446
00:28:57,680 --> 00:28:59,300
My player is lagging around.

447
00:28:59,300 --> 00:29:03,230
And that's because I don't have network ownership over my character.

448
00:29:03,230 --> 00:29:04,700
This really sucks.

449
00:29:05,360 --> 00:29:08,570
Of course, I am able to set the network ownership back to my player.

450
00:29:08,570 --> 00:29:15,140
I just need to pass it a player instance so I could do game dot players that player one and update the

451
00:29:15,140 --> 00:29:16,880
network owner for my humanoid report.

452
00:29:16,880 --> 00:29:21,830
And now everything's smooth again, because I have network ownership over the physics of my character

453
00:29:21,830 --> 00:29:27,770
model, I can also set the network ownership to be automatic, again using a function called set network

454
00:29:27,770 --> 00:29:28,970
ownership auto.

455
00:29:28,970 --> 00:29:34,520
So if I do that, then the network ownership for my character is now automatic, which will still be

456
00:29:34,520 --> 00:29:38,810
set to my computer because it's my character model.

457
00:29:38,810 --> 00:29:45,440
But as for like these parts in the workspace, I could do workspace dot physics part two and set the

458
00:29:45,440 --> 00:29:47,240
network ownership back to automatic.

459
00:29:47,240 --> 00:29:52,850
So now it should have alleviated the control over the physics of that part from the server, and it

460
00:29:52,850 --> 00:29:56,450
should have given it to my player because my player is like right next to it.

461
00:29:56,450 --> 00:30:01,430
So now if I start interacting with it, you can see how much more smooth and responsive it is.

462
00:30:02,240 --> 00:30:04,700
You can see that the physics is working just fine.

463
00:30:05,180 --> 00:30:09,080
But if I were to set network ownership back to the server.

464
00:30:10,390 --> 00:30:16,990
Or set network owner, I believe set network, set network owner back to the server and then try interacting

465
00:30:16,990 --> 00:30:17,530
again.

466
00:30:17,830 --> 00:30:21,280
You can see it's really buggy and glitchy and it doesn't work that well.

467
00:30:21,280 --> 00:30:26,110
So network ownership is a really crucial idea to understand when you're making anything in your games

468
00:30:26,110 --> 00:30:32,950
relating to physics, for example, vehicles in your game, the driver of the vehicle should have network

469
00:30:32,950 --> 00:30:39,880
ownership over it, because if it doesn't, you'll likely end up with laggy, unresponsive, and kind

470
00:30:39,880 --> 00:30:43,780
of crappy vehicles that aren't responding to your input that well.

471
00:30:43,780 --> 00:30:50,320
Like if you had the physics solely be calculated by the server, then your vehicles might not even work

472
00:30:50,320 --> 00:30:50,950
at all.

473
00:30:51,250 --> 00:30:57,310
Now, I'm not an expert on physics, but just by learning and experimenting with the assembly linear

474
00:30:57,310 --> 00:31:02,800
velocity of parts, messing around with linear velocities and vector forces, and understanding the

475
00:31:02,800 --> 00:31:08,950
concept of network ownership allows you to really make whatever kind of strange and wacky physics related

476
00:31:08,980 --> 00:31:12,100
type stuff you want in your game, maybe like a Ferris wheel.

477
00:31:12,100 --> 00:31:18,190
Or you could make like a moving platform, or add zero gravity for specific players in your game and

478
00:31:18,190 --> 00:31:19,030
stuff like that.

479
00:31:19,030 --> 00:31:23,920
So if you're interested in learning more about these different instances and how you can use them to

480
00:31:23,920 --> 00:31:29,440
manipulate physics in your game, all the documentation for them will be linked in this lecture, as

481
00:31:29,440 --> 00:31:32,320
well as documentation for a network ownership.

482
00:31:32,320 --> 00:31:36,520
Other than that, I hope you enjoyed this lecture and I will see you next time.