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When wanting to include a deformable- type object in a dynamic simulation, Reactor, before allowing that object in as a legitimate member of a deformable body collection, will insist that that object first have one of three specific types of modifiers applied to it-- that modifier type being determined by the way in which we are wanting the object to react or specifically respond during the simulation. In this video, we'll take a look at those three special modifier options. In the scene that I have on the screen named Soft Body Modifiers, I have created three different objects wanting each to respond in a different way as they deform during a dynamic simulation.
There's a curtain on the left, a rope in the middle, and a foam toy over on the right-hand side. Starting with the curtain, if we create a cloth collection and attempt to add the object to it, you'll notice that Reactor won't allow it to happen. Now in a previous video, we discovered that if an object is first selected when a collection is added, that object will be included in that collection. So let's see how this will work. We'll select our curtain, then head over to the Reactor toolbar on the left. You will find the Cloth Collection second one down. Let's go ahead and click on that.
Now, something's wrong here. In the past when we had an object selected, then added the collection, the Collection icon would rest directly on top of whatever we had selected. You don't see that in our situation here. The Cloth Collection is basically saying, "I'll accept your curtain geometry, but before I do so, I am going to first need you to apply the appropriate modifier." So let's go ahead and do that. In the Reactor toolbar, a little further down, we'll find the Cloth Modifier. The icon will look like a shirt with a M in its middle. Once we find that button, with the curtain still selected, we'll go ahead and click.
If we now focus our attention over in the Modify settings, you'll see, indeed, in the stack, the Reactor cloth has been added in. Now that we have the needed modifier in place on our curtain, we can now go back and try to add that Cloth Collection one more time. Back up to the icon and we'll click. Okay, there is the Cloth Collection icon that I was expecting. Why don't we now go back and select the Curtain and we'll check out the Modifier Settings over on the right? Looking at the Cloth Modifier controls, you'll see that we've got a setting for the weight of the Curtain. Reactor calls that Mass.
Directly below that, Friction would determine how the Curtain would respond if it rubbed up against something else in the scene. The Air Resistance setting would control how the Curtain would respond if coming into contact with a wind force. In the sections called Force model and Fold Stiffness, these are going to be your controls that would control how the Curtain would stretch and fold when moving. And a little further down below, you've got a series of attachment or constraining methods if you wanted to secure your curtain to something else in the scene.
So basically, a handful of controls that would allow our curtain geometry to specifically react during an animation as if it was made of cloth. For things like ropes or chains, we've got another modifier type to work with, something Reactor calls a Rope Modifier. Let's see if we can't apply that to our rope geometry, then throw the object into our rope collection. Now I've been using the Reactor toolbar over in the right. This time I am going to change gears using the Quad menu. For that, I'll simply hold down the Shift+Alt keys and right-click. With the rope object selected, I'll select Rope Modifier up at the upper left-hand quadrant.
Now that we have our modifier in place, let's also add the Rope Collection. That again can be done using the Shift+Alt+Right-click. With the Rope Modifier, we have settings for the geometry's weight, thickness, and friction. There is also a Stiffness control and something called Damping, which determines how quickly an object settles back into its original position when bent or twisted around. Also, like we saw with the Cloth Modifier, a little further down in the controls, we've got several different methods to constrain our rope to another object in our scene.
We'll be looking at the specific options for gluing things together when we get to our projects. Lastly, for the foam toy, it, too, before making its way into the appropriate soft body collection, we'll need a special modifier-- in this case something referred to as a Soft Body Modifier. With that toy selected, I'll again Shift+Alt+Right-click. Up in the menu on the top left, you'll see the Soft Body Modifier. Let's go ahead and apply that. Then to get into a collection, again, we'll use the Quad menu. Staying up on the top left, but a little further down, let's click on, this time, Soft Body Collection.
Okay, back to selecting the foam toy. With the Soft Body Modifier, you've got similar settings for measuring and simulating an object's mass, stiffness and friction. You also have a couple of different options, or methods, as to how Reactor will go about actually deforming the object's geometry, using either a mesh-based calculation--which works well when changing the shape of an object that isn't extremely heavy as far as its mesh weight-- or use instead a type of free-form deformation lattice control to direct the movement of the underlying mesh.
As a rule of thumb, the FFD-based way of going about doing things will typically be your best option when working with objects having 200 or more faces. And as with the two modifiers we saw just prior, the Soft Body Modifier also offers the same constraining controls when wanting your object locking onto something else in your scene--those controls being found a little further down. So those are your three soft body modifiers and a few other things you need to be aware of when wanting to include deforming mesh surfaces in a simulation.
Remember, unlike rigid body objects, soft body geometry will always need a special modifier applied to it before being allowed in the game.
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