Any GameObject must contain a Rigidbody to be influenced by gravity, act under added forces via scripting, or interact with other objects through the NVIDIA PhysX physics engine A system that simulates aspects of physical systems so that objects can accelerate correctly and be affected by collisions, gravity and other forces. More info See in Glossary.
Rigidbodies allow your GameObjects to act under control of the physics engine.
Video Game Physics Tutorial - Part III: Constrained Rigid Body Simulation | Toptal
This opens the gateway to behaviors such as realistic collisions and varied types of joints A physics component allowing a dynamic connection between rigidbodies, usually allowing some degree of movement such as a hinge. Manipulating your GameObjects by adding forces to a Rigidbody creates a very different feel and look than adjusting the Transform Component A functional part of a GameObject. A GameObject can contain any number of components.
Unity has many built-in components, and you can create your own by writing scripts that inherit from MonoBehaviour. More info See in Glossary directly. The biggest difference between manipulating the Transform versus the Rigidbody is the use of forces. Rigidbodies can receive forces and torque, but Transforms cannot. Transforms can be translated and rotated, but this is not the same as using physics. Every GameObject has a Transform.
This is why you should only be using one or the other. Changing the Transform while using physics could cause problems with collisions and other calculations. Rigidbodies must be explicitly added to your GameObject before they will be affected by the physics engine. Now your object is physics-ready; it will fall under gravity and can receive forces via scripting, but you may need to add a Collider An invisible shape that is used to handle physical collisions for an object.
More info See in Glossary or a Joint to get it to behave exactly how you want.
When an object is under physics control, it moves semi-independently of the way its transform parents move. If you move any parents, they will pull the Rigidbody child along with them. However, the Rigidbodies will still fall down due to gravity and react to collision events. To control your Rigidbodies, you will primarily use scripts A piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like.
More info See in Glossary to add forces or torque.
For some situations, mainly creating ragdoll effects, it is neccessary to switch control of the object between animations and physics. For this purpose Rigidbodies can be marked isKinematic. While the Rigidbody is marked isKinematic , it will not be affected by collisions, forces, or any other part of the physics system. This means that you will have to control the object by manipulating the Transform component directly. Kinematic Rigidbodies will affect other objects, but they themselves will not be affected by physics.
For example, Joints which are attached to Kinematic objects will constrain any other Rigidbodies attached to them and Kinematic Rigidbodies will affect other Rigidbodies through collisions. Colliders are another kind of component that must be added alongside the Rigidbody in order to allow collisions to occur. If two Rigidbodies bump into each other, the physics engine will not calculate a collision unless both objects also have a Collider attached.
Collider-less Rigidbodies will simply pass through each other during physics simulation. View the Component Reference page of any individual Collider for more specific information:.
Video Game Physics Tutorial - Part III: Constrained Rigid Body Simulation
Compound Colliders are combinations of primitive Colliders, collectively acting as a single Rigidbody. They come in handy when you have a model that would be too complex or costly in terms of performance to simulate exactly, and want to simulate the collision of the shape in an optimal way using simple approximations. To create a Compound Collider, create child objects of your colliding object, then add a Collider component to each child object.
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This allows you to position, rotate, and scale each Collider easily and independently of one another. When the Rigidbody parent is moved around by forces, the child Colliders move along with it. The typical solution is to use primitive Colliders for any objects that move, and Mesh Colliders for static background objects.
Note: Compound colliders return individual callbacks for each collider collision pair when using Collision Callbacks. Continuous collision detection is a feature to prevent fast-moving colliders from passing each other. This may happen when using normal Discrete collision detection, when an object is one side of a collider in one frame, and already passed the collider in the next frame.
To solve this, you can enable continuous collision detection on the rigidbody of the fast-moving object. Set the collision detection mode to Continuous to prevent the rigidbody from passing through any static ie, non-rigidbody MeshColliders. A complete spec like this is great for some use cases and useful to have as meshula mentioned , but I believe a simpler spec also has its uses easier to implement, still covers a lot of cases. As a separate conversation, I noticed your spec does not have a way to lock motion on particular axes.
Bullet calls this linear factor and angular factor, and may be useful to include. PhysX supports locking motion as well, but I didn't think that was a generic concept. Every object in the spec is a 'Node' and every node can have a set of 'additional properties'. The idea is that engine specific concepts can be expressed under the additional properties fields.
That said, if locking motion on an axis is a generic enough concept, it could be added to the base spec. To clarify what my task at hand is. For an internal project at work I need a way to express rigid body physics in a generic way that can be run on multiple physics engine backends. I believed this was also a goal of the GLTF project, so I felt there was an opportunity to 'kill two birds with one stone', since the goals seemed largely the same.
I do not think my current spec is complicated, in fact I thought it was quite simple and generic, but capable of expressed many complex rigid body systems. If there is no desire for this effort to be integrated into GLTF, I can stop contributing to this effort here. My tasks for my work project remain the same. I believed this was also a goal of the GLTF project, so I felt there was an opportunity to 'kill two birds with one stone', since the goals seemed largely the same In my opinion jratcliff 's proposal is both simple and generic for the expressed goal of providing a superset of physics engines' capabilities.
This has the advantage that glTF assets can be expected to work very broadly, but is clearly less expressive. Whether that same "subset" approach is right for physics, I don't know. There are features described here that cannot be expressed in JS physics engines like Cannon.
Having both may be a reasonable compromise. Or perhaps there is some way for one to "extend" the other? I'm not quite sure how to handle the protobuf and XML requirements, and would defer to you on that. The alternative is that some things may be expressed as higher-abstraction wrappers around glTF, as 3D Tiles do to combine geospatial metadata and glTF assets, rather than as extensions. I am just one voice, and I find a more limited physics subset to work better for my current needs. I am sure other people would love a more complete physics spec. Also, I would not say that your spec is complicated; it just includes more e.
I would say "complete" or "comprehensive" is a better description than "complicated. I agree with meshula in that maybe trying to add any kind of rigid body representation to glTF might go beyond what's really needed. Sometimes we must remember the KISS philosophy. Good things are tiny. Let's think in terms of Model-View-Controller; Everybody would consider having "Employee" profile information embedded within the photography of that employee as a crazy design.
That being said. Having rigid body information embedded in the glTF file makes more sense from the point of view of how current artistic pipelines work today: I can see a 3D artist creating a 3D model, and including a rigid body layer so the artist can export everything in a single shot. Another matter is whether to include the rigid body information within the gltf schema or not The same happens for the graphics engine, it needs to skip the rigid body information data. With separated files, each domain would load exactly what it needs, without interferences from the other. Based on donmccurdy 's comment , it sounds like it could be fine to have a very simple Blender physics extension and the full-featured extension - if the former isn't easily designed as a subset of the later, or the former can be done much more quickly.
europeschool.com.ua/profiles/xorunofy/sexyz-hombre-come-solo.php Does this make sense or not? It's not a perfect analogue, but perhaps this is like glTF common materials vs. Both are valuable and expected to be widely implemented. The group is OK with having two extension, especially this early in the glTF physics ecosystem where we need to get more implementation experience to flush things out - it could benefit from different approaches.
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Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. New issue. Copy link Quote reply. The basic components of any rigid body system can be described in the following outline: Simulation properties Each physics engine defines certain global properties which control how that system performs. Many of these properties tend to be unique for each different physics engine supported.
Includes things like gravity, solver iteration count, and other global settings. Data Resources objects with large amounts of binary data Triangle meshes Convex Hulls Heightfields Physics Materials Defines physical properties of a material surface, friction, etc. Geometries physical geometric representations for rigid bodies or parts of a compound rigid body Plane Box Sphere Capsule Cylinder Triangle Mesh Convex Hull Heightfield Rigid Body can be static, dynamic, or kinematic Each rigid body has one, or more, geometries and their associated unique properties; such as what material to use, what scale, etc.
When Emission In World is on, Maya makes extra computations to convert world space to object space coordinates. To disable dynamics for all rigid bodies controlled by a solver. This turns off the effect of fields, collisions, and rigid body constraints for the rigid bodies it controls. Show in Contents. Add to Favorites. Home: Maya User's Guide.
Related Guide to Dynamic Simulations of Rigid Bodies and Particle Systems
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