so I have this dynamic body, that I just want to know when an object collides with it, but even if this object collides with it, the dynamic body will always move at the same time and will only affect by gravity and the floor.
I tried kinmestic bodies and sensor, but it's not affected by gravity. I can add gravity but how can I add also that it will collide with the floor and stop?
I don't care what, but I most find a solution for that. Thanks.
There is no need for sensor in your case. You have to implement the b2ContactListener. Here is the manual how to do it: http://www.box2d.org/manual.html
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player and object both have colliders and rigidbodies, object has position and rotation locked, player has only rotation locked. When the player goes to the blocks, the player goes through the blocks, although they do give a bit of resistance. To move the player im setting the rigidbody's velocity, and doing that in FixedUpdate.
i have no idea why this is happening, any ideas?
main part of the code is:
rigidBody.velocity = new Vector3(direction.x, rigidBody.velocity.y + (-Gravity * Time.deltaTime), direction.z);
(direction is determined by the WASD keys, and i'm using my own gravity)
First of all, you do not need to multiply the velocity by time.DeltaTime, because you are moving your object in the FixedUpdate() method; Which uses fixed time intervals since the physics engine does not run in sync with the regular game engine. Also, both objects do not need rigidbodies in order to collide with one another. I suggest looking at your collision matrix in settings and verifying that everything you need collision for is checked correctly. As others have said as well, check your kinematics on the rigidbody.
A last suggestion for working with your own gravity. Do not change the actual gravity value of the game engine. It is typically recommended that you use a multiplier variable and apply it to the constant gravity already set by the physics engine. If you are completely editing the gravity, than maybe consider using a character controller instead.
I guess it has something to do with what the documentation says "In most cases you should not modify the velocity directly, as this can result in unrealistic behaviour".
Try to use AddForce() or similar functions to alter the properties of the rigid body. Colliders etc will then work as expected.
I have a cube with Rigidbody attached to it would slide slightly whenever I pressed the play button. If I leave it for awhile, it would slide to other side of the screen.
Anyone know how to solve this problem without using the "freeze position"? I don't know what I messed up in my project...
This is what the object looks like:
Note: I need to use the gravity.
Thank you!
Heh! The solution here is:
You had a rigidbody on the floor :)
You don't do that :) Never.
If the "floor" surface is flat, then,
it will not slide.
You've got something strange going on, such as
"floor" is NOT flat
a feature like "Wind" turned on
perhaps other objects invisible in the scene you have forgotten about are nudging it
PhysX does not have a "mind of it's own". There is some simple reason it is moving.
Let's say the "floor" is indeed on an angle, so it SHOULD move, but you WANT it to NOT move.
What you obviously do:
Just as in the real world, put something there to stop it moving.
A small invisible wall will do the trick. That's PhysX!
Usually rigidbody sliding happens when a lower rigidbody has lower mass than a higher rigidbody (forcing down the lower rigidbody). Typical problem with player having say mass 80 jumping on a cube with mass 1. In this case the collision is so violent that the cube will probably fly out (not only slide).
The situation is very similar to the real world. Try to stay on a box of milk if you have 120 kg (ok, ok, 80 :) ).
When you try to eliminate this behavior, you need either increase the mass of the lower object or decrease the mass of the higher one or set the lower rigidbody to kinematic.
The solutions above is not proper way of solving the problem. Unity has more features of physics than mass. If you get sliding on movement or because of other objects you should add proper drag value on your rigidbody. For example , lets say you have blocks spawning over top of other blocks and this creates horizontal sliding. In my case I add drag of 1 to the objects which has mass of ~ 1 kg. It depends on the scene and you should try different values on your case. Do not use bigger values and angular drag if it is not important.
I have an object that, after receiving its respective input, it moves this way:
mov = new Vector3((Input.GetAxis("Horizontal") * vel), 0, 0);
transform.position += mov;
But, I want it to bounce back, once it collides with an object.
I´ve made the procedures already (OnCollisionEnter2D(Collsion2D col){bla bla...}), but I need help with what happens on the collision (bouncing back the object)....
I´ve tried giving the collided object a bouncing material, but it just slows it a bit, my guess is that because of the constant force given by the acceleration.
Greetings.
If you move the object with transform.position what you are doing is basically a "teleport" so it will ignore the bouncing material. If you want it to bounce you have to write the physics code to detect a collision and change the movement or you can do addforce to move the object and it will detect collisions and react automatically.
you are teleporting the object at the current time. instead you should use the Rigidbody.addForce this will add a force in the specified direction thus if you do the opposite direction will "bounce" of the object. Another option would be to create a physics material then not bother with the code.
You are not using materials, right?
See if the content of this post may help you, the OP is using a formula using Raycast and the answer guides him to use the Raycast with Layers Maks:
2D bouncing formula doesn't work properly
There is this one also with fixed angles (like Pong), but it uses material (with values: friction: 0, bounciness: 1):
https://gamedev.stackexchange.com/questions/70294/get-gameobject-to-bounce-of-colliders
But if nothing makes sense and you are going crazy and might want to start from zero, there is this official video tutorial on bouncing and sliding in 2D:
https://unity3d.com/learn/tutorials/modules/beginner/2d/sliding-bouncing-2d
I have a sphere build from multiple objects. What I want to do is when I touch/click an object, that object should find all adjunctive objects. But because none off them are moving, no collision detection can be used.
I can't find a way to detect these adjunctive objects even when the colliders do collide with each other, as I can see that in the scene. I tried all the possibilities, but none off them are working, because no objects are moving.
Is there a way to check for manual collision detection, or is there some sort of way to let Unity3d do the collision detection automatically?
You could keep a list of all those objects, then when your event happens you can send messages to all them to do what you want them to do.
Lets assume you want your sphere to break into little pieces. You send a Force message to the sphere. Then you use Newton's Laws of motion and find out how much velocity each piece gets. Remember velocity is a vector thus it has direction.
This is how I would do it and still keep the right amount of control over what happens in my game/simulation. Remember F = ma.
you could use RaycastHit (http://docs.unity3d.com/Documentation/ScriptReference/RaycastHit.html) for your collision, this also works on non-moving objects but it needs more performance
You can add rigidbody to every objects; when you touch one of them, give a force onto it, then it is going to move and trigger event of the adjacent objects.
for the reason you do not want to move the object you touch, you can cancel movement in the OnCollider or OnTrigger event handler function.
I managed to work around this by checking the distance from the selected object and all other objects that are part of the sphere. If the distance is below a certain value, then it is an adjunctive object.
Although this is certaintly not fool proof, it works without problems so far.
I am sorry I was not clear enough. Thanks for all the advice what so ever.
newbie to iPhone game development and Box2D here.
I'm developing a game in which I can move (drag) otherwise stationary objects that can collide with other objects.
How do I make these objects stationary in a Box2D world with gravity while maintaining their ability to collide with dynamic bodies?
One random thought is to exert a force equal to gravity on these objects all the time. Any better or simpler approaches? Will static bodies help?
Static bodies will collide with dynamic objects but not other static objects. That sounds like what you want, but it's not clear from your description what the "other bodies" in question are.
You cannot disable gravity on a per-object basis; exerting a force equal to the opposite of gravity will usually work but can, due to rounding errors, accumulate small velocities. A better approach is to set gravity to 0 and manually apply a gravitational force on the objects you do want affected by gravity.