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In Getting Started with Reactor in 3ds Max, Steve Nelle shows how to create realistic dynamic simulations that have objects recognize, collide and react to coming into contact with each other in 3ds Max animation projects. This course includes a detailed explanation of both rigid and soft body dynamics, reactor's various collection types, using constraints and soft body modifiers, and how to adjust and control a dynamic simulation's accuracy. Four start-to-finish projects are also included in the course, which show practical techniques for breaking objects apart, creating cloth simulations, adding rippling water effects to a scene, and more. Exercise files accompany the course.
Let's get our project started by setting up our cloth simulation. We're going to be using a file named Cloth Curtains. All the geometry needed for our scene has been modeled and ready to go, which will give us an opportunity to concentrate on setting up the actual dynamic simulation. Now, although a deforming cloth type object would seem a logical candidate for a soft body simulation, Reactor offers a special collection and modifier type for cloth-type sims. Let's start by taking our front view full screen, then zooming in specifically on our right-hand side curtain.
We'll make the viewport changeover using the Alt+W keyboard shortcut. Okay, let's talk about geometry real quick. In simulating cloth, Reactor can use any 2D surface: polygons, patches, NURBS-- it makes no difference. What does make a difference is that that geometry needs to be two-dimensional. So whatever you use, it's got to be flat. Another thing that's important is the amount and the layout of the lines, as both influence how well the cloth will fold and stretch. Because of the way that our curtains are going to fold and be pulled to the side, in our situation here we'll be able to get away with using a wireframe design that's very evenly laid out.
By that, I mean that all of our mesh edges run straight acrossed, both up and down, and left or right. Most of the time though, when simulating a cloth surface, you'll find that your mesh will fold and stretch more realistically if your wire design isn't too contiguous, meaning that having your edges traveling in a bunch of various directions will actually make for a better-deforming cloth object. The reason for that is that cloth has a tendency to fold along the pattern of its edges. So for something like a shirt or bed sheet, evenly spaced and squared-off edges just don't typically make for as realistic-looking cloth deformation.
Our curtains though, will fold just fine with a more standard wire layout. Now behind the curtain and in front of the orange curtain rod, you'll see a series of what look like yellow circles. They're actually cylinders that are going to serve as the clips that'll end up pulling each of our curtains to the side. The clips, which will be identified as rigid body objects in our sim, will need to somehow be secured to their respective curtain. We're going to do that using a constraining mechanism on the cloth modifier that we'll be assigning to each curtain.
Once the individual curtains are assigned to the appropriate clips, we'll then be able to animate the position of the clips, which will in turn pull the curtains back to the side, having them bunch up or gather together as they do. After the clip attachments have been made, we can then get our curtains into a collection--that collection being the ticket to being able to run our sim. So let's set things up. We'll select the curtain on the right, assigning a Cloth Modifier from the Reactor toolbar. The Cloth Modifier, located a little further down in the toolbar, will look like a t-shirt with a small M to its side.
Now, I'd like to run this through a preview. That's going to require us though, to put this guy into a collection. What type? That's right. Cloth surfaces go into Cloth Collections. With the curtain still selected, back in the toolbar on the left, we'll go to the top. Once we are there, we'll find the Cloth Collection. It will be the second one down, the icon looking like a shirt with a C on it. Once you find that, you can go ahead and click. Okay, let's run a quick preview here and see what happens. To get to the Preview window, we'll simply use the Shift+Alt+Right-click shortcut.
Now, because the curtain is resting a little bit low in the Preview window, I'll use the left and middle mouse buttons to better position my object. Now, I'll demo that. Once I have it in better position, I'll go ahead and press P for playback. Well, that's not going to cut it. The curtain, not having anything to hold on to, simply drops like a rock. This is where the curtain rod clips will come in to play.
Each clip will be assigned to a series of individual vertices on the curtain's surface, the verts chosen being the ones that are encloses proximity to each clip, and that'll be what it'll hold each curtain in place: certain vertices on the curtain being constrained to certain clips hanging in front of the rod. Now in order to be able to make our vertex identifications on the curtain, we're going to need to be in Vertex mode on our Cloth modifier. Let's go ahead and get there. We'll select the curtain. Then head over to the right-hand side of the screen.
In the Modifier stack, the top entry, reading Reactor Cloth, has a Plus sign to its left-hand side. Go ahead and click on that. When you do so, you'll see the Vertex subobject level. You'll then want to select that. Okay, now we can drop little further down to the Constraints area on the modifier. The Cloth modifier gives you four different ways to constrain a cloth surface to something else in your scene. Being that our curtain clips are going to be seen as rigid body objects in our simulation, we'll click on the button that says Attach To Rigid Body.
That will open up a box directly below with that new RigidBody entry showing in the list. Because we're going to be having several of these attachments on each curtain, let's go ahead and rename our entry. To do that, you'll simply single-click on it a couple of times until you get into the naming mode. Once we're there, let's go ahead and name this RT, then a space, then the number One. You can then press Enter to lock in the new name. We'll then want to go back and click on that new name as a way of telling Reactor that it's the newly created attachment that we are wanting to work on.
When you select it, it'll highlight with the blue background. Now back in the viewport, we'll want to select at least a couple of vertices around the specific curtain clip that will bind back to that area on the curtain. Now, we're working on the curtain clip on the far right side. In Vertex mode, let's now window-select the six vertices that surround that clip. After doing so, the vertices should turn red. Okay, a little higher up in the modifier in a section called Attach To Rigid Body, click on the None button, then in the scene click on the clip that's right underneath that vertex selection.
If you've made a good connection, you should now see the name Clip RT 1 under where it says Rigid Body. So that's how the attachment is made. We can now do the same thing for the other two clips on the right-hand curtain. I'll drop back down to the Constraints category, clicking again on Attach To Rigid Body. That'll create a second attachment. Now let's rename this. We'll call it Right Two. We'll then go back and select the attachment, then drop back into our scene. Now for the second middle yellow clip, we'll again select the six vertices that surround it.
For that last row, you can either go to the left like I've done or to the right; it shouldn't make much difference. To now identify that second clip, we'll go back up to where it says Attach To Rigid Body, click on the None button, then back in the scene, clicking on that second middle yellow clip. Now once you've done so, go back to the right and verify, under Rigid Body, it reads Clip Right Two. Let's now go ahead at our third attachment. For this one, I'll name it Right Three.
We'll reselect it, then go in for our vertices. Now for the clip on the left, why don't we grab let's say the eight vertices that surround it. We'll start on the upper left-hand corner, pulling down to the second row, then over four. Very good! Now we'll go back up in the Modifier column, making that identification back to our clip. We'll click on None, then we'll click on the clip itself. Now after doing so, again, for verification purposes, we'll go back to the right-hand side and verify under Rigid Clip it reads, Clip RT 3.
Okay, let's now run another preview and see what happens. I'll right-click using the Shift+ Alt combo to get to my preview. As the warning message is telling us, we need to get our curtain clips into our rigid body collection of their own being that they are going to be a needed part to our simulation. So we'll close the message box, hitting H to go to select by name. From the list, we can then drop halfway down, selecting Clip RT 1, RT 2, and RT 3. Once we've done that, we'll click OK, down in the bottom-right corner.
Now that will give us our selection. Now, we're going to have to create that rigid body collection. In the Reactor toolbar over in the left, there it is, way at the top. We'll verify the name of the icon, then click. Okay, let's see what happens this time going through a preview. Even in the preview goes a little bit slow due to the calculations taking place, now I am playing things back, you see the curtain definitely has a little more stretch to it than we probably want. We'll be able to adjust that, but the good part about the Preview is the cloth is staying attached to the clips.
Let's now do the same thing for our left-hand curtain. Adding a modifier, making the attachment assignments and adding it to the Cloth Collection. We'll close the window, then go back into our scene. Once I have better situated the left- hand curtain, I'll go ahead and make the selection and add the Cloth Modifier. This time around, I'll use my Quad menu with the Shift+Alt+Right-click selection. Okay, back to the Modifier column. Let's get into Vertex mode. Working in the Constraints category down below, we can now click on Attach To Rigid Body.
Okay, same thing here. We'll rename the attachment Left One. We'll then, working again in Vertex mode, select the six vertices that surround that right-hand clip. Let's go to a little closer in, so we can better make our selection. Once we've got those vertices and our crosshairs, we can then go back and make the attachment back to that right-hand-side clip. Let's do the same thing for the middle clip. Down to Attach To Rigid Body.
This one we'll name Left Two. We'll then reselect the attachment entry, going back to make a Vertex selection. Again, why don't we select the six verts that surround the middle clip? We can then go back up on the right and identify the middle clip as what we want these vertices to attach to. Again, before going on, make sure to return to a right-hand side, verifying that the Rigid Body reads, in this case, Clip Left 2.
Very important, you don't want to be dropping that vertex selection somewhere along the road. Let's now slide over and work on the clip on the left. Once in position, we'll return to Attach To Rigid Body, naming our third attachment Left 3. We'll then go identify in this case the eight vertices that'll be attached to the selection. And as a final step, we'll then identify the clip on the left. Okay, once we've finished up with our attachments, we'll get out of Vertex mode, then head back to our scene to select the Cloth Collection.
With the Collection selected, back on the right using the Pick button, we'll now click on that left-handed side curtain. Before running another preview, we're going to want take these three clips, getting those also into our Rigid Body Collection. Using H, I'll select the RBCollection, then over on the right click on the Add button. From the list, we'll simple go about halfway down, identifying the three clips. Okay, let's run another preview and see how things turn out.
On play, you'll see the things are turning out looking pretty good. Now, with that second curtain coming into action, we're getting a little bit now even slower version of our playback. So let's do this. As a setup, because we really don't even want to work on one curtain at time, let's go back to our Rigid Body Collection, this time deleting--at least temporarily--the right-hand curtain. I'll need to go back and then select the Cloth Collection, then on the right click on the name Curtain Right.
Once I've got that highlighted, I'll go down below on the right-hand side clicking on Delete. Okay, that'll, at least for the time being, take that right-handed side curtain out of the simulation. So I am liking the way things are turning out. Both curtains now seem to be holding together fairly well. Now, the next thing to do is going to be to animate the clips pulling back the curtains. We'll do that keyframing in our next video. Let's save our scene up as Cloth Curtains01, so we can take the file with us.
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