Understanding the dynamics engine
Video: Understanding the dynamics engineThe dynamics module in CINEMA 4D is part of the Studio bundle, and it allows CINEMA 4D to simulate the behavior of objects as if they were in the real world affected by gravity. Anytime you hear that word Simulate or Simulation, it means that the computer is trying to recreate behavior from the real world. Because of that recreation, the calculations that go on behind the scenes are incredibly complex. It also means that you lose a certain amount of control that you have over your scene. There's a lot of things that you can do with simulations that you can't do with keyframes, but you often lack the control that you have with keyframes.
- Final thoughts
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CINEMA 4D Essentials with Rob Garrott is a graduated introduction to this complex 3D modeling, rendering, and animation program, which breaks down into installments that can be completed within 2 hours. In this installment, Rob introduces particles, a cluster of objects used to simulate effects like snow, sparks, fog, or fire, and dynamics, which allow you to define how objects interact with their environment. The course covers creating a splash effect with particles, working with more advanced Thinking Particles, and how to understand the difference between the dynamics system's rigid bodies and soft bodies.
- Working with particle forces and the Emitter object
- Using Thinking Particles with the MoGraph Tracer
- Understanding the Dynamics engine
- Combining Thinking Particles with Dynamics
- Creating dangling objects with spline dynamics
Understanding the dynamics engine
The dynamics module in CINEMA 4D is part of the Studio bundle, and it allows CINEMA 4D to simulate the behavior of objects as if they were in the real world affected by gravity. Anytime you hear that word Simulate or Simulation, it means that the computer is trying to recreate behavior from the real world. Because of that recreation, the calculations that go on behind the scenes are incredibly complex. It also means that you lose a certain amount of control that you have over your scene. There's a lot of things that you can do with simulations that you can't do with keyframes, but you often lack the control that you have with keyframes.
It's a lot like trying to bowl a ball down the lane. You know you can throw the ball down the lane but you don't always know that you can hit those pins. And that's what the Dynamics Engine is like, it's just like bowling. So how does the Dynamics Engine work? Let's add a very simple cube to the scene. And at the heart of the Dynamics Engine is the Dynamics tag. Let's right-click on the Cube and go to Simulation Tags, and then go to Rigid Body. All of these options--Rigid Body, Soft Body, Collider, and Ghost--are all contained under the same tag. Even though their icons are different, they're all based on the same tag.
The tags icon changes, depending on what type of settings you put under it. So let's start off with a Rigid Body. And when we add that to the scene it looks like nothing happened, except that when I hit Play, my cube falls away. It's now being affected by gravity. And that gravity is controlled by the Project Settings. Let's hit Cmd+D or Ctrl+D on the keyboard, and underneath the Project Settings, under the Dynamics option, is the gravity in the scene. And I can control that gravity. I'll leave it at 1,000 for now. Let's rewind back to zero, and you can see that my cube falls away.
And that cube would keep on falling off to infinity, unless it collides with something, and that's a very important aspect of the Dynamics Engine is that it allows for object collision. Let's go to the Primitives icons and add a Plane to the scene, and let's make that Plane a Collider. So we go to the Plane and right-click, and go to Simulation Tags, and then add Collider Body. Let's rewind and hit Play, and you can see that my cube falls but, it falls even faster. The reason that it falls even faster is that when two dynamic objects start off the scene in the exact same location, the Dynamics Engine doesn't know how to resolve it and so it freaks out and just throws the objects off.
You never know what direction they're going to fly off in but they do take off in strange ways. So what we need to do is rewind back to zero, let's grab the cube and raise it up on the Y axis, let's drag it up out of frame and let's expand out a little bit, and then hit Play. And you'll see that now the cube falls down and it strikes the Plane as if it were a solid floor. Let's rewind back to zero. Because our Cube and the Plane are directly lined up, when it hits the Plane it just bounces and stays flat. If I rotate my cube, let's rotate it a little bit so that the point is down first, rewind back to zero and hit Play.
You'll see that the cube point now hits the Plane, and it bounces and rolls around and tumbles. Let's hit Stop. That illustrates another important point about the Dynamics Engine, is that it allows you to adjust the starting positions of your objects. Now all of this dynamic simulation and calculation is being contained within the Dynamics tag, let's take a look at that. And under the Dynamics tag, we've got the Dynamics Properties. So the Enable option determines whether or not the tag is active. And I'll turn that off.
And because this is the Plane, when I hit Play, you'll see that the cube will fall but it will no longer make contact with that collider. The Plane's ability to interact with Dynamic objects has been disabled. Let's turn that back on and rewind back to zero. Now let's select the Cube's Dynamics tag, and when I click on that one, you notice that the Dynamic option has reverted to on. So on the Plane, if I click on that tag, you can see that this is Off. If I go to the Cube, it's on again. Off and on.
And you notice that the icons are different. If you watch that location right there on the screen, the icon will change. So the only difference between the two tags, the one on the Plane and the one on the Cube, is this Pull Down: Off, On, and Ghost. Ghost Objects allow you to create invisible objects in the scene that will behave with dynamic ways. And that's a great way to create a collision with something that doesn't necessarily need to be seen. Underneath the Collision options, you have the ability to adjust how the object interacts with other Dynamic objects in the scene. I'm going to go the Bounce Settings and change that from 50 to, say, 100.
And I'm on the cube, and so when I rewind and hit Play, the cube's going to bounce higher. You can scrub that value even higher, it can go beyond 100%, I just clicked and dragged. And because I did that while the cube was playing, you saw it froze for a minute while I was scrubbing the value. And then when I let go, the cube bounces down and then springs off, it's got way too much energy. It's returning way more energy than it had when it started. Let's bring that back down to 100%, it's a little more realistic value. Friction determines how sticky the surface that the object is bouncing off of.
If I make this Plane really large, let's select the Plane and hit T on the keyboard to bring up the Scale Tool, and make the Plane really large and rotate it. When I rewind back to zero and hit Play, you'll see that the object kind of bounces and slides off. Let's stop that. Now we'll go to the Plane object, and on its Collision options, we'll change the Friction from 30 to something like 100. Let's rewind back, and let's look at this from the side so we can see it a little bit better, and let's hit Play.
You see that it's not sliding off quite as quickly. Let's go to the Cube object and do the same thing for its Friction. You can see that now, it feels like the Plane is maybe made out of sand paper or something like that. It's grabbing on to that cube and they're interacting a little bit more dynamically with each other because they have more stickiness to them. The Forces section allows you to add forces to the scene, and those refer to the Particle Forces under the Simulate Menu.
So let's rewind back to zero and rotate the Plane under the Coordinate Properties back to zero. And then hit Play to confirm we still have the correct reaction, and we do. Let's rewind back to zero. And go to the Simulate Menu and under the Particles Submenu, let's add in a Wind Object. Now the Wind Object blows along its Z Axis. If I Drag this up out of the floor -- let's grab the Axis Band and drag it up out of the floor, you can see that it is oriented along the Z Axis.
Now because the Falloff is set to Infinite on the Wind object, it's going to blow in the entire scene. So it really doesn't matter where it is in relationship to the cube. The only thing that matters is the direction of the Z Axis. Now let's go back to the Cube, and under the Force tab, you see because this mode is set to exclude, any forces that I add to the scene, when I hit Play will automatically start to affect the cube. Let's go to the Wind object and crank up, under its Object Properties, the Wind Speed. You see that it blows the cube so hard that it never even makes it to the ground.
Let's rewind back to zero and change the Wind Speed from 100 back down to something like 50 or so. Hit Play. The Dynamics Engine in CINEMA 4D is both incredibly powerful and easy to use. The key is that all of that power and ease of use is contained within those tags. The properties there will help you do amazing things.
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