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Adding joints to rigid bodies

From: Unity 4.3 Essential Training

Video: Adding joints to rigid bodies

When we're working with physics, one of the powerful Now with the spherical colliders on, I'll get box colliders on the rods.

Adding joints to rigid bodies

When we're working with physics, one of the powerful things we can do is to chain objects together. What this will let us do for example, is take this mobile sculpture, and link the pieces together, so it hangs from the ceiling. And when the player knocks into it, it will wobble back and forth. The pieces can rotate, and will move, but are fixed by their rods on that wooden hanger. It's a collection of sphere, and very very small cylinders for the rods. And a roughly modeled series of arcs in wood. WIth a wood base that goes onto the ceiling.

I've already put in the correct materials. So the eyes are on the spheres. There's chrome, and there's the same dark wood we've used elsewhere. I'm ready to get the colliders on. In this object, I've avoided putting on a mesh collider in the FBX. And so instead I'm going to put on custom sphere and box colliders, so it collides with the rigid bodies correctly. I'll start out by getting the spherical colliders on all the eyes, picking them, choosing Component > Physics and Sphere Collider. Now with the spherical colliders on, I'll get box colliders on the rods.

They're actually five sided cylinders made in Maya and then softened so that they look round. But they're small enough that a box will work nicely. I'll pick the first one, choose component, physics, box collider, and then I'll repeat it with the other three. Finally, I'll get a box collider on the hanger. Although it's actually two boxes that are bent, one big box that work nicely because it is at the same level all the way around roughly. I'll put a box collider on the hanger right at the top and finally one on the top mounting block. Now get rigid bodies on everything. It's simply a matter of going through and picking each one and putting a rigid body component on.

Once all the pieces have a rigid body component on, I can go through and set up the hinges. I also should get a material on. So that they react correctly with the right friction and the right mass. It’s really up to you, what order you'd like to do it in. As long as everything is on, it’ll work nicely. One note here on the top, this mounting block. Although, it’s a box collider, and has that rigid body onto it, I’m going to turn off gravity and freeze the position. This way, it’s fixed at ceiling, and I’ll freeze position on all three axes, and rotation.

Its supposed to stick in place, but let that first hangar rod hang from it correctly. Now I'll get my hinge joints on. I'll start out with the first sphere and I'm going to turn off the lighting so I can see a little better. On this sphere then, I'll choose component, physics and hing joint. We've got a couple different joints here. Hing joints, Fixed joints, spring joints. And then Characters and Configurables. A hinge is one of the simplest ones. It simply allows freedom of movement and rotation on multiple axes, as needed.

Things can be hinged together. A fixed joint, then, joins rigidly, rigid bodies. And finally, a spring, as the name suggests. Is springy and allows objects to snap out and come back. I'll pick Hing joint here and in that Hing joint, we can see it's got an anchor. It's got a spring and a motor. And there's also limits for breaking force. If we need objects to actually break and fly apart, we can put in that force there. Right now, the break force and torque are infinity, meaning it can't be broken.

This way we'll knock into it, but it can't come apart. The Hing joint is noticeable by the small orange arrow and its right up here at the base of the connecting rod. This is where I had set the pivot for that sphere and so it defaults to there until we move it around using the anchor or axis. Now in the connected body in the hinge joint I'll pick that connecting rod. This is IO1, and so it connects to hanger rod 01. I'll click to select, and the only thing that's available in the rigid body section are objects that I put a rigid body on to.

So, I'll pick hanger_rod1. And now there's that connection. Then I'll pick the hanger rod and do the same. Component, physics, Hingd joint. I had put the pivot for this up at the top, and that's where that Hing joint originates. Then I'll pick it's wood hanger as it's connecting piece. I'll repeat this process with the other ones, and then connect in the top hanger. I've added hing joints onto all of the eye's hangars, wood hanger, rods and up to the ceiling base. This way everything should hang, and I'll give it a quick test once I turn back on the building.

And then see what I need to add in my physic materials. I'll pick the master building, and turn on its visibility again. I'll make sure that this is up at the ceiling by selecting that whole sculpture, and pulling it up. Now, I'll press Play and see how it looks. The sculpture bobbles gently. It's already wobbling and the eyes will come over and look around. I may want to start those in a different position. But it looks kind of neat. It works. And when I jump, I can bang into it. And cause them to move around considerably. It does need a little damping.

We can see in here it's getting a little crazy in the motion and that's because those objects really don't have much mass. It's going to sit there and sort of bobble forever and the colliders will freak out a bit and collide with each other. I'll put in some damping. I'll start out with the eyes. Scroll down and look in the rigid body, there is a drag there, and i'll put up the drag to 0.5. I'll add the drag to the other eyes and see how it looks. I've added drag onto all the eyes and I'm ready to add drag and a little bit of resistance on the wood hanger and other connecting rods.

Part of dealing with physic materials then in our rigid bodies is making sure things don't fly around. So I'll put some drag on this hanger too. It's a little heavier so a drag of one should work. I'll give it a test before I put the drag on the chrome hanger rods and I'll see if it behaves any better. It looks better so far. The eyes look around and it's not quite shaking in such a jittery way. I like the way it's looking. And we can just probably bump these as we go by. And they'll knock around a bit without getting too crazy.

We should probably add drag on the other objects, so that they really are kind of A little more stationary, but it looks like the drag is slowing it down nicely. Finally, let's get some physic materials on to complete this. I'll click on the eyes and go into the material in the Sphere collider, and in my physic materials, I'm going to choose rubber. I'll put the rubber material on the other eyes here, and then try this one more time. Finally, before I try it, I'll get a physic material of wood on the hanger. We should really go through and make sure we have materials on anything that really counts here.

These rods are probably okay on their own. Now in a test, my mobile is a little less jittery. I should probably bring up the mass and a few other things, but I like how it's moving. And when I knock into it, it definitely gets a little crazy, but then settles down. So, it's kind of neat to be able to bounce off the art a bit, knock into it accidentally. We can use our physics to add some life to the game. Adding the ability to, fling things. Knock into things, push stuff over, and otherwise affect our world and let the animation happen very naturally.

Being generated by the physics engine.

Show transcript

This video is part of

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Unity 4.3 Essential Training

78 video lessons · 10269 viewers

Adam Crespi

Expand all | Collapse all
  1. 2m 57s
    1. Welcome
    2. What you should know before watching this course
    3. Using the exercise files
      1m 24s
  2. 21m 21s
    1. Designing the game
      4m 39s
    2. Setting the project
      4m 9s
    3. Exploring the Hierarchy, Scene, and Inspector windows
      5m 45s
    4. Creating and transforming objects
      6m 48s
  3. 21m 34s
    1. Organizing the Assets window
      2m 55s
    2. Exporting objects from 3D modeling programs
      8m 33s
    3. Importing and configuring models and textures
      4m 54s
    4. Setting properties for models and textures in the Inspector
      5m 12s
  4. 29m 8s
    1. Introducing the game environment
      4m 27s
    2. Placing the player controller
      4m 29s
    3. Publishing project settings
      5m 32s
    4. Adding sky and fog
      8m 17s
    5. Fine-tuning the First Person Controller
      6m 23s
  5. 57m 25s
    1. Creating the terrain geometry
      3m 29s
    2. Forming the topography
      9m 54s
    3. Painting the terrain textures
      7m 9s
    4. Painting trees and forests
      10m 55s
    5. Painting grass, shrubs, and 3D geometry
      9m 38s
    6. Painting detail meshes
      8m 46s
    7. Adjusting terrain settings
      7m 34s
  6. 39m 45s
    1. Creating materials and assigning shaders
      8m 56s
    2. Handling multiple materials
      7m 13s
    3. Adding textures to a material
      3m 57s
    4. Manipulating textures
      5m 20s
    5. Adding reflections to materials
      8m 1s
    6. Creating lit materials
      6m 18s
  7. 47m 12s
    1. Creating GameObjects
      5m 2s
    2. Understanding components
      6m 15s
    3. Using colliders for barriers
      6m 22s
    4. Using colliders for triggers
      8m 1s
    5. Exploring physics
      8m 22s
    6. Working with Physic materials
      5m 3s
    7. Adding joints to rigid bodies
      8m 7s
  8. 20m 33s
    1. Setting up prefabs for animation and batching
      5m 8s
    2. Animating an object
      6m 32s
    3. Adjusting timing in an animation
      3m 50s
    4. Animating transparency and lights
      5m 3s
  9. 11m 58s
    1. Importing skinned meshes
      4m 51s
    2. Separating animations into clips and states
      3m 14s
    3. Creating transitions between states
      3m 53s
  10. 30m 22s
    1. Customizing ambient light
      2m 59s
    2. Creating the sun using a directional light
      5m 49s
    3. Using layers and tags for lighting
      3m 32s
    4. Adding spot and point lights
      4m 25s
    5. Using point lights for fill
      4m 30s
    6. Adding and fine-tuning shadows
      5m 10s
    7. Creating lighting effects with cookies
      3m 57s
  11. 9m 15s
    1. Adding scripts to GameObjects
      2m 42s
    2. Using correct script syntax
      6m 33s
  12. 23m 7s
    1. Setting up a 2D project
      3m 13s
    2. Importing sprites
      2m 30s
    3. Slicing in the Sprite Editor
      3m 6s
    4. Layering sprites and setting the sorting order
      5m 12s
    5. Creating 2D colliders
      3m 12s
    6. Adding 2D physics
      2m 25s
    7. Animating 2D elements
      3m 29s
  13. 30m 25s
    1. Creating light shafts and sunbeams
      5m 20s
    2. Using ambient occlusion to add gravity
      4m 37s
    3. Adding depth of field
      8m 40s
    4. Applying motion blur
      5m 46s
    5. Tuning color for mood
      6m 2s
  14. 38m 16s
    1. Exploring water effects
      7m 36s
    2. Working with wind zones
      2m 8s
    3. Using an audio source
      4m 3s
    4. Creating a sound zone
      5m 59s
    5. Triggering audio
      3m 37s
    6. Adding audio effects
      3m 13s
    7. Creating particle systems
      2m 26s
    8. Adjusting particle systems
      9m 14s
  15. 25m 23s
    1. Setting up occlusion culling
      5m 52s
    2. Enabling batching to reduce draw calls
      3m 28s
    3. Testing in the game window using statistics
      4m 27s
    4. Building a development build and debugging
      6m 0s
    5. Building the executable
      5m 36s
  16. 49s
    1. Next steps

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