I've searched for quiet some time now around the web for a solution to my problem, and couldn't find any sufficient enough resource to help me.
I'm developing a co-op RPG game in Unity 3D, using the UDP library https://github.com/RevenantX/LiteNetLib , and I managed to do a client-server connection, where I send vector of my player movement (time calculation is not applied- so the server can handle it on its own tick) to the server, and it calculates the new position where the character should be, and afterwards I broadcast to all players the new same vector that I sent to the server so they can also calculate the physics by themselves.
The problem I'm running into is that the movement seems very laggy and sometimes miscalculated.
I'm not sure if its due to my local PlayerController script or due to bad network, or bad design where I should actually send the new absolute position of the client.
I know this is a hard question, I am hoping for some guidelines or expertise of developers who tried to create multiplayer games themselves,
I should also note, that cheating doesn't concern me because it is a coop game and not a competitive one.
Thanks in advance for any help.
Here is a snippet of my local PlayerController code:
void Update()
{
// Get Input for axis
float h = Input.GetAxis("Horizontal");
float v = Input.GetAxis("Vertical");
// Calculate the forward vector
Vector3 camForward_Dir = Vector3.Scale(UnityEngine.Camera.main.transform.forward, new Vector3(1, 0, 1)).normalized;
Vector3 move = v * camForward_Dir + h * UnityEngine.Camera.main.transform.right;
if (move.magnitude > 1f) move.Normalize();
// Calculate the rotation for the player
move = transform.InverseTransformDirection(move);
// Get Euler angles
float turnAmount = Mathf.Atan2(move.x, move.z);
transform.Rotate(0, turnAmount * RotationSpeed * Time.deltaTime, 0);
if (_characterController.isGrounded)
{
_moveDir = transform.forward * move.magnitude;
_moveDir *= Speed;
}
_moveDir.y -= Gravity * Time.deltaTime;
var delta = _moveDir * Time.deltaTime;
_characterController.Move(delta);
if (!IsMoving())
{
//_wasMoving = false;
return;
}
// we send the move direction so that the server and other client`s can calculate for themselves
OnPlayerMoved?.Invoke(_moveDir, Time.deltaTime);
}
As I mentioned in my comment, people who still need help with this topic might want to view this demo https://github.com/RevenantX/NetGameExample it demonstrates how to create 2D player sync which can easily be applied for 3D, the code belongs to RevenantX,
and it relies on a UDP library which he also created for the community.
Related
I have implemented the following tutorial in Unity (2D) attempting to create a rope swinging platformer: https://gamedevelopment.tutsplus.com/tutorials/swinging-physics-for-player-movement-as-seen-in-spider-man-2-and-energy-hook--gamedev-8782
void FixedUpdate()
{
Vector2 testPosition = playerRigidbody.position + playerRigidbody.velocity * Time.deltaTime;
Hooked(testPosition);
}
private void Hooked(Vector2 testPosition)
{
Vector2 t = new Vector2(tetherPoint.position.x, tetherPoint.position.y);
Debug.DrawLine(tetherPoint.position, playerRigidbody.position);
float currentLength = (testPosition - t).magnitude;
if (currentLength < tetherLength)
{
currentLength = (playerRigidbody.position - t).magnitude * Time.deltaTime;
}
else
currentLength = tetherLength;
if ((testPosition - t).magnitude > tetherLength)
{
Vector2 x = (testPosition - t).normalized;
testPosition = new Vector2(x.x * currentLength, x.y * currentLength);
playerRigidbody.velocity = (testPosition - playerRigidbody.position) * Time.deltaTime;
playerRigidbody.position = testPosition;
}
}
It seems to function correctly on the downward swing but when the player begins to travel upwards they become stuck floating in the air and don't drop to the middle of the arc. The swing also does not propel them very high on the other side even when dropped from height.
EDIT (Further clarification): Interestingly When the player is dropped from the other side of the tetherPoint it stops in the same spot, this time only half-way down. It's as if the player is being pulled toward a single position even when manually moved in the editor while playing no matter the direction.
EDIT: User John cleared up my concerns about deltaTime.
I've tried examining the change in variables during play but I just can't figure out why it's not working correctly. I think the issue lies somewhere in my interpretation of the original psudeo-code to C#.
Another question on the same tutorial has been asked previously but unfortunately that users implementation was very different than mine: Game rope swing physics acting weird
EDIT: Since posting I've updated the code to use AddForce and MovePosition instead but it's still the same.
playerRigidbody.AddForce((testPosition - playerRigidbody.position) * Time.deltaTime);
playerRigidbody.MovePosition(testPosition);
It looks like you're using Time.deltaTime from a method that is called from FixedUpdate. What you want to use instead is Time.fixedDeltaTime.
FixedUpdate is called at a set interval (eg. 50fps) for physics updates, but regular Update is called at a different varying frequency (up to hundreds of times a second if you've got a fast computer/simple game).
Time.deltaTime is used for the Update method, and so the value of it can be different each time Update is called, as the time between Update calls varies.
However, because FixedUpdate is called at the same interval each time, Time.fixedDeltaTime is constant and (normally) much larger than Time.deltaTime. Your code doesn't work well with Time.deltaTime, as it doesn't represent the actual difference in time between each FixedUpdate call, but Time.fixedDeltaTime should work.
As a side note, you're correct that you should be multiplying by the time delta rather than dividing. the time delta should be multiplied when calculating positions (eg. for the Vector2 testPosition assignment and the currentLength calculation), but for calculating the velocity you should be dividing the time delta (because velocity = distance/time).
I'm trying to figure out simple custom 2D physics for platformer. At the moment I'm using ray casts to figure out collision between the player and map. However using ray cast has some problems. For example, if the player is falling (has somewhat high downwards velocity) its unable to pick up holes in the wall because it moves past them due to going too far down to be detected as empty space.
One solution is to move to tile based system instead of using ray casts but I would preferably not to do so.
So I'm wondering is there some kinda solution to figure out empty holes in wall, even small edge ones without huge performance impact.
High quality drawn illustration, assume leftwards velocity:
Physics2D.BoxCast is how I would tackle this. It does what you expect, instead of a ray it calculates as if a full box was traversing the distance.
Usage is very similar to raycasting. Example:
public Collider2D mainCollider;
public Vector2 velocity;
void Update() {
Vector2 origin = new Vector2(transform.position.x, transform.position.y);
Vector2 size = mainCollider.bounds.size;
Vector2 direction = velocity * Time.deltaTime;
float maxDist = velocity.magnitude;
var hit = Physics2D.BoxCast(origin, size, 0, direction, maxDepth);
if (hit == null) {
transform.position += direction;
} else {
transform.position += direction.normalized * hit.distance;
}
}
If boxes are not your taste, there's also a Physics2D.CapsuleCast and Physics2D.CircleCast.
I have a 2D scene that consists of 4 sprites, each with a box collider.
I then have a prefab that is simply a sprite of a circle with a 2D circle collider.
Finally I have a script named Atmosphere attached to my main camera that will fill the box with lots of instances of the prefab and give them a velocity in a random direction.
using UnityEngine;
public class Atmosphere : MonoBehaviour
{
public GameObject Molecule;
void Start()
{
float x = -4.5f;
while (x < 4.5f)
{
float y = -4.5f;
while (y < 4.5f)
{
var inst = GameObject.Instantiate(Molecule);
inst.transform.position = new Vector3(x, y, 0);
var rb = inst.GetComponent<Rigidbody2D>();
float xForce = Random.value * 2f - 1f;
float yForce = Random.value * 2f - 1f;
rb.AddForce(new Vector2(xForce, yForce) * 100f);
y += 0.5f;
}
x += 0.5f;
}
}
}
For a while the dots bounce around against each other and the edges of the box.
But after a while they eventually get stuck to the edges of the box.
Both the box and balls and the box walls have the same physics material
Which has zero friction and a bounciness of 1.
Why do they stick to the walls, and how can I stop it from happening?
Download Unity 3D demo
UPDATE
If I drop a single molecule into the box with the following script attached it gets stuck to the wall immediately.
[RequireComponent(typeof(Rigidbody2D))]
public class Molecule : MonoBehaviour
{
Rigidbody2D RigidBody2D;
void Start()
{
transform.position = new Vector3(0, 1, 0);
RigidBody2D = GetComponent<Rigidbody2D>();
float xForce = Random.value * 2f - 1f;
float yForce = Random.value * 2f - 1f;
RigidBody2D.AddForce(new Vector2(-.25f, -0.25f) * 100f);
}
}
Unity3D has a velocity threshold. Objects with a velocity below this threshold won't bounce etc.
The solution is to go to Edit > Project Settings > Physics 2D and to set the Velocity Threshold lower.
EDIT - The real solution:
So I was doing some reading on integration techniques and it hit me: The energy you're losing is quite likely coming from numerical inaccuracies stemming from several approximation techniques compounded.
I'm guessing the continuous collision detection algorithm is mostly to blame, floating-point error accumulation, but probably also from numerical integration techniques.
What you're trying to achieve is elastic collision, which means that it satisfies conservation of energy as well as momentum. The trick is going to be for you to add a script to every object that preserves the energy of the system by adding error-correcting velocity over time. Whether you actually use the energy route or not is up to you, there are a number of ways to track and modify the energy resulting in a change of velocity. Momentum would be the would be the easiest to track in my opinion. What you're trying to achieve is elastic collision, which means that it satisfies conservation
i.e.
Make a component that preserves the scalar quantity of kinetic energy or momentum (it'll probably produce the same results)
When you initialize all the particles with a velocity, make sure to save the starting momentum in the particle's script. I would save the scalar quantity for simplicity, so just use the length of velocity
Every frame, in the update event check the velocity of the rigid body. Find the change in momentum or change in energy and add the -difference and apply it to the object.
I doubt you'll have to work on collision events as well, especially if you use the exact same mass for every object. Here's a link with an example where someone corrected unity's friction-less physics using conservation of energy https://answers.unity.com/questions/168393/frictionless-physics.html
colliders may be stuck in each other for the reason of low contact offset, go to edit-project settings-physics2d and increase the default contact offset a little bit, 0.12 for example, it was work for me.
cheers
I have already this function from this question. I changed the sign of the rotation:
void rotateBotConnector()
{
Vector3 diff = (player.transform.position - botConnector.transform.position).normalized;
float rot_z = Mathf.Atan2(diff.y, diff.x) * Mathf.Rad2Deg;
botConnector.transform.localRotation = Quaternion.Euler(0f, 0f, -(rot_z - 90f));
}
But the problem is, that now my object follows the player on the XZ plane but when the rotation reaches a certain degree, left or right, the object stops to rotate towards my player.
For better understanding: http://imgur.com/vWaqc31
Why not just use:
var target : Transform;
transform.LookAt(Vector3(target.transform.position.x, target.transform.position.y, transform.position.z);
It seems a lot easier than using euler. This way you look at target's x & y but transform your z.
Also I'm no expert with euler but it seems like it is limited to a 90 degree turn and I think this may be the reason why:
Quaternion.Euler(0f, 0f, -(rot_z - 90f));
Unless you have absolute necessity to rotate via angles maybe you'd rather go with manipulating the forward vector of the object, it's easier to understand the logic this way:
void rotateBotConnector()
{
Vector3 targetForwad = botConnector.transform.position - player.transform.position;
targetForward.y= 0f;
targetForward.Normalize(); // <-- this is very expensive function try avoid using it whenever possible
botConnector.forward = Vector3.Lerp(botConnector.forward, targetForward, Time.deltaTime));
}
once again, if you are short on cpu cycles you may want to go for trying to calculate angles instead of vectors. But in most cases this is ok. (the code needs a spell checking)
I am having trouble keeping game objects inside of a contained space. When they reach the edge, there is some momentary push back but then they will go right through the wall.
I am using a Box Collider on the player, and a Mesh Collider for the level's wall. I am having issues with both a Player Character (a space ship) that the movement is controlled by the player. And with projectiles, which are fire and forget moving at a constant speed.
This is my movement code for my player. It is being run in the FixedUpdate() function.
//Movement
haxis = Input.GetAxis("Horizontal") * speed;
vaxis = Input.GetAxis("Vertical") * speed;
moveVector.x = haxis;
moveVector.z = vaxis;
if(moveVector.magnitude > 1)
{
moveVector.Normalize();
}
rigidbody.MovePosition(transform.position + moveVector * speed);
With the bullets, they are given a velocity and the engine calculates their moviements. They are using Box Collider and it is set as a Trigger so they don't have physics. But I use OnTriggerEnter to destroy them.
//Projectiles without physics collisiions
function OnTriggerEnter (other : Collider) {
Destroy(gameObject);
}
Some, but not all of the bullets will be destroyed when hitting the mesh collider wall. The player will sometimes hit it and stop, but can usually push through it. How can I make the collisions with the mesh collider work every time?
Collision with fast-moving objects is always a problem. A good way to ensure that you detect all collision is to use Raycasting instead of relying on the physics simulation. This works well for bullets or small objects, but will not produce good results for large objects.
http://unity3d.com/support/documentation/ScriptReference/Physics.Raycast.html
Pseudo-codeish (I don't have code-completion here and a poor memory):
void FixedUpdate()
{
Vector3 direction = new Vector3(transform.position - lastPosition);
Ray ray = new Ray(lastPosition, direction);
RaycastHit hit;
if (Physics.Raycast(ray, hit, direction.magnitude))
{
// Do something if hit
}
this.lastPosition = transform.position;
}
I have a pinball prototype that also gave me much trouble in the same areas. These are all the steps I've taken to almost (but not yet entirely) solve these problems:
For fast moving objects:
Set the rigidbody's Interpolate to 'Interpolate' (this does not affect the actual physics simulation, but updates the rendering of the object properly - use this only on important objects from a rendering point of view, like the player, or a pinball, but not for projectiles)
Set Collision Detection to Continuous Dynamic
Attach the script DontGoThroughThings (https://www.auto.tuwien.ac.at/wordpress/?p=260) to your object. This script cleverly uses the Raycasting solution I posted in my other answer to pull back offending objects to before the collision points.
In Edit -> Project Settings -> Physics:
Set Min Penetration for Penalty to a very low value. I've set mine to 0.001
Set Solver Iteration Count to a higher value. I've set mine to 50, but you can probably do ok with much less.
All that is going to have a penalty in performace, but that's unavoidable. The defaults values are soft on performance but are not really intented for proper simulation of small and fast-moving objects.
How about set the Collision Detection of rigidbody to Continuous or Continuous Dynamic?
http://unity3d.com/support/documentation/Components/class-Rigidbody.html
So I haven't been able to get the Mesh Colliders to work. I created a composite collider using simple box colliders and it worked exactly as expected.
Other tests with simple Mesh Colliders have come out the same.
It looks like the best answer is to build a composite collider out of simple box/sphere colliders.
For my specific case I wrote a Wizard that creates a Pipe shaped compound collider.
#script AddComponentMenu("Colliders/Pipe Collider");
class WizardCreatePipeCollider extends ScriptableWizard
{
public var outterRadius : float = 200;
public var innerRadius : float = 190;
public var sections : int = 12;
public var height : float = 20;
#MenuItem("GameObject/Colliders/Create Pipe Collider")
static function CreateWizard()
{
ScriptableWizard.DisplayWizard.<WizardCreatePipeCollider>("Create Pipe Collider");
}
public function OnWizardUpdate() {
helpString = "Creates a Pipe Collider";
}
public function OnWizardCreate() {
var theta : float = 360f / sections;
var width : float = outterRadius - innerRadius;
var sectionLength : float = 2 * outterRadius * Mathf.Sin((theta / 2) * Mathf.Deg2Rad);
var container : GameObject = new GameObject("Pipe Collider");
var section : GameObject;
var sectionCollider : GameObject;
var boxCollider : BoxCollider;
for(var i = 0; i < sections; i++)
{
section = new GameObject("Section " + (i + 1));
sectionCollider = new GameObject("SectionCollider " + (i + 1));
section.transform.parent = container.transform;
sectionCollider.transform.parent = section.transform;
section.transform.localPosition = Vector3.zero;
section.transform.localRotation.eulerAngles.y = i * theta;
boxCollider = sectionCollider.AddComponent.<BoxCollider>();
boxCollider.center = Vector3.zero;
boxCollider.size = new Vector3(width, height, sectionLength);
sectionCollider.transform.localPosition = new Vector3(innerRadius + (width / 2), 0, 0);
}
}
}
1.) Never use MESH COLLIDER. Use combination of box and capsule collider.
2.) Check constraints in RigidBody. If you tick Freeze Position X than it will pass through the object on the X axis. (Same for y axis).
Old Question but maybe it helps someone.
Go to Project settings > Time and Try dividing the fixed timestep and maximum allowed timestep by two or by four.
I had the problem that my player was able to squeeze through openings smaller than the players collider and that solved it. It also helps with stopping fast moving objects.
Edit ---> Project Settings ---> Time ... decrease "Fixed Timestep" value .. This will solve the problem but it can affect performance negatively.
Another solution is could be calculate the coordinates (for example, you have a ball and wall. Ball will hit to wall. So calculate coordinates of wall and set hitting process according these cordinates )
Try setting the models to environment and static. That fix my issue.