Trying to align the in game physics with devide gravity in realtime.
Inspired by "How to change global gravity properties at runtime?" post using following code during _process/_physics_process
var acc_gravity = Input.get_gravity().rotated(Vector3(-1, 0, 0), deg2rad(90))
PhysicsServer.area_set_param(get_world().get('space'),
PhysicsServer.AREA_PARAM_GRAVITY_VECTOR, acc_gravity.normalized())
PhysicsServer.area_set_param(get_world().get('space'),
PhysicsServer.AREA_PARAM_GRAVITY, acc_gravity.length())
But the physics just went into very weird behavior, kind of slowmotion or outright nothing move. Seems these parameter setting does much more than changing a number; and can only be set at ready but not updated constantly. Is there a workaround? Thanks.
For what I understand you want a constantly changing gravity. I suggest to not use gravity at all. Instead simply use add_central_force in _physics_process:
add_central_force(Input.get_gravity().rotated(Vector3(-1, 0, 0), deg2rad(90)))
This is something that differs between 2D and 3D physics in Godot: in 3D forces are reset every physics frame.
So, if I do this in a RigidBody2D:
func _ready() -> void:
add_central_force(Vector2.LEFT * 10)
I'll see the RigidBody2D accelerate to the left…
But if I do this in a RigidBody:
func _ready() -> void:
add_central_force(Vector3.LEFT * 10)
I'll see the RigidBody move a little and then stop, or not move at all (depending if it is using Bullet or GodotPhysics).
Thus, since you are working in 3D, you don't need to keep track of the prior forces you added.
Related
in this video, https://youtu.be/klBvssJE5Qg I shows you how to spawn enemies outside of a fixed camera. (this is in GDscript by the way) How could I make this work with a moving camera? I wanna make a zombie fighting game with a moving camera and zombies spawning outside that.
I would really appreciate help with this.
I've tried researching on the internet about how to do it, but I just didn't find it.
N/A..................................
After looking at the video, I see they are using this line to spawn:
Global.instance_node(enemy_1, enemy_position, self)
This suggest to me a couple thing:
The position is probably either relative to the self passed as argument or global.
There must be an Autoload called Global that I need to check to make sure.
And the answer is in another castle video.
In the video Godot Wave Shooter Tutorial #2 - Player Shooting we find this code:
extends Node
func instance_node(node, location, parent):
var node_isntance = node.instance()
parent.add_child(node_instance)
node_instance.global_position = location
return node_instance
And thus, we are working with global coordinates global_position. Thus enemy_position is used as global coordinates.
Ok, instead of using enemy_position as global coordinates we are going to use it as local coordinates of the Camera2D (or a child of it). Which means you need a reference to the Camera2D (which I don't know where do you have it).
You could make your code in a child of the Camera2D, or take the transform of the Camera2D using a RemoteTransform2D. Either way, you could then work in its local coordinates. Thus you would do this:
Global.instance_node(enemy_1, to_global(enemy_position), self)
Or you could have a reference by exporting a NodePath (or in the newest Godot you can export a Camera2D) from your script and set it via the inspector. So you can do this:
Global.instance_node(enemy_1, camera.to_global(enemy_position), self)
Where camera is your reference to the Camera2D.
In the following section of Arena.gd:
func _on_Enemy_spawn_timer_timeout():
var enemy_position = Vector2(rand_range(-160, 670), rand_range(-90, 390))
I believe you can add the X and Y coordinates of the camera to their corresponding random ranges in the enemy position Vector2. This will displace the enemy depending on where the camera is currently located.
You can get the position of the camera with this:
get_parent().get_node("Name of your camera").position
When this is all put together:
func _on_Enemy_spawn_timer_timeout():
var enemy_position = Vector2(rand_range(-160, 670) + get_parent().get_node("Name of your camera").position.x, rand_range(-90, 390) + get_parent().get_node("Name of your camera").position.y)
Keep in mind that you might need to displace the values in the following while loop as well. I hope this helps.
I am working on a physics game and encountered a strange bug: sometimes, after firing a lot of bullets, collision detection starts to fail.
As can be seen in the following GIF, the collision works only on half the platform, which is very strange. Also, the Box2D debug renderer is enabled and it can also be seen that the platform is a single body.
Here is how I get this bug to happen, as it only happens only after firing lots of bullets (in the beginning everything works fine):
Notes:
- the bullet has the bullet field set to true
- I set the player's bullet field to true, did not make a difference
- the player is 1 meter by 1 meter
- the player and the bullets are DynamicBodies and the platforms are StaticBodies
- the map is near to (0, 0), though it goes a bit in the negatives (-1.5), I doubt it matters
- the categoryBits and maskBits are correct (the collision should happen, and it does happen, but glitches)
- after the bullets disappear, the number of bodies is the same as when the game starts (so they are actually destroyed)
- the World's gravity is (0, -25f)
- the game runs at 60fps
Here is the Box2D timestep code, similar to the stepping code from the libGDX wiki:
companion object {
private const val TIME_STEP = 1f / 300f
private const val VELOCITY_ITERATIONS = 6
private const val POSITION_ITERATIONS = 2
}
private var accumulator = 0f
override fun update(deltaTime: Float) {
accumulator += Math.min(deltaTime, 0.25f)
while (accumulator >= TIME_STEP) {
world.step(TIME_STEP, VELOCITY_ITERATIONS, POSITION_ITERATIONS)
accumulator -= TIME_STEP
}
}
I tried changing:
- TIME_STEP to a lower value, like 1/60f
- VELOCITY_ITERATIONS a bit higher, to 8
- POSITION_ITERATIONS a bit higher, to 6
- VELOCITY_ITERATIONS and POSITION_ITERATIONS to 100
and there was no (obvious) difference.
Concern:
The bugged platform seems to start behaving like a bullet (it doesn't collide with other bullets or with the player), at least halfway. So could its categoryBits and maskBits be changed on-the-fly, after a lot of world.createBody() and world.destroyBody(), maybe due to pooling?
So what should I try for the collision not to fail in this case?
I finally managed to fix it.
The solution I found was to loop through every entity that has a body and call refilter(), which seems to fix it:
engine.getEntitiesFor(Family.one(BodyComponent::class.java).get()).forEach {
it.body.body.fixtureList.first().refilter()
}
In the future, I could call refilter() only when needed (if I can determine when I have to call it) instead of calling it every frame, but it works for now.
It looks like you should call refilter() after you change the filterData of a body (changing its categoryBits or maskBits) outside the FixtureDef, but I don't seem to be doing that (or maybe I am missing something), so it is a bit weird.
I have been having great difficulty creating a jumping system whereby the user can tap the jump button for a small jump and hold it down for a higher jump.
I stumbled upon this topic:
https://gamedev.stackexchange.com/questions/13277/variable-height-jumping-in-side-scrollers
Which greatly helped me develop the following code:
PlayerMovementTimer = [NSTimer scheduledTimerWithTimeInterval:0.005 target:self selector:#selector(movePlayer) userInfo:nil repeats:YES];
[JumpButton addTarget:self action:#selector(jumpPlayer:) forControlEvents:UIControlEventTouchDown];
[JumpButton addTarget:self action:#selector(stopJump:) forControlEvents:UIControlEventTouchCancel | UIControlEventTouchUpInside | UIControlEventTouchDragExit];
- (void)movePlayer
{
CGFloat playerY = Player.center.y + PlayerYV;
if(playerY > 264) {
PlayerYV = 0;
playerY = 264;
}
if(playerY < 264) {
PlayerYV += 0.048f - PlayerYD;
}
if(HoldingJump && PlayerYV < 0 && PlayerYD + 0.0018f < 0.048f) {
PlayerYD += 0.0018f;
}
Player.center = CGPointMake(Player.center.x + PlayerXV, playerY);
}
- (IBAction)jumpPlayer:(id)sender
{
if(Player.center.y == 264) {
PlayerYD = 0;
PlayerYV = -2.25;
HoldingJump = true;
}
}
- (IBAction)stopJump:(id)sender
{
HoldingJump = false;
}
The code seems to work (some of the values need a bit of fine tuning but I haven't gotten round to that yet). The only problem is that the movement appears to be slightly jerky (even on the real device) and that when the player is at the top of the jump they accelerate really slowly and no values I put seem to be able to get the jump to look smooth like on Mario games.
Please take a look at the code and see if I am missing something obvious, or if there is a more efficient method of controlling movement than an NSTimer calling a void function. Also, is setting a UIImageView's position to a float value bad?
Thanks.
So there are quite a few things wrong here. First, yes, you should never be setting the origin of an ImageView or any other UI element to a coordinate position that is a fractional pixel. This causes sub-pixelling which will blur your image. To avoid this, all CGFloats should be rounded to the nearest whole number using roundf() or other similar rounding functions.
Another issue I can see is that you're setting Player.center. I hope for your sake that Player is not an ImageView cause you're going to be making your life harder. As mentioned above, when the origin of a frame is not set to a CGFloat that is a round number, you'll get sub-pixelling. When you use the center property, you can easily cause yourself to get on a bad origin value. For example, if I have a 11 by 11 image and set it's center to (11,11), the origin will get set to (5.5,5.5) and will cause sub-pixelling. Easy ways to avoid this is just do the math to place the origin correctly and make sure to round the CGFloats that you feed into it (or use CGRectIntegral on the frame before you set it).
A third issue here is that the timer is being called 0.005 seconds. Let's assume you want this game to run with 60 FPS. 60 FPS translates to about 0.0167 seconds. The timer is calling the method three times more often then it would need to even if you wanted 60 FPS and additionally, calling this method so often could be causing some of your jerky motion.
Now in terms of getting a "Mario" like jump, what you really need to do is look at getting a dedicated physics engine since if you're using the code above, you don't appear to have one. What a physics engine would do is it would apply a constant "gravity" which will help make the player jumps look and act more realistically. You would, when a player presses a button, apply an impulse up on the player character. The use of impulses would also simplify your work as you could apply impulses in different ways depending on how long they hold the button, etc. The code above is simply trying to get around this problem instead of addressing the real issue of you not having a physics engine.
Go investigate cocos2D and Box2D as a possible physics engine you could use. There are a wealth of resources on cocos2D+Box2D and there is a developer who even has made a tutorial on using cocos2D to create a Super Mario clone that should give you some basic understanding of how physics engines work: http://www.raywenderlich.com/15230/how-to-make-a-platform-game-like-super-mario-brothers-part-1
I am working on a pool game of sorts. To create a table, I have used cubes as sides. I want to use the inbuilt physics engine to get those sides interact with the balls. Sadly I am unable to get it working.
Here is what I have done. I created cube as side, and a sphere for ball. To move the sphere, I am using rigidbody.MovePosition function. both the cube and sphere have colliders and rigidbody attached, and gravity turned off.
Sphere movement is fine, but when it collides with cube, it makes the cube fly. Since the cube is supposed to be an immovable wall, I constrained all axes rotation and movement. But, using constraints cause physics engine to go bonkers. Instead of sphere coming to stop or moving in opposite direction, it simply passes through the cube. Clearly, something is wrong, and I need help figuring out the same.
Thanks in advance.
Here is the code used to move the sphere.
public float movePower = 10.0f;
// Update is called once per frame
void Update ()
{
if(Input.GetKey(KeyCode.LeftArrow))
{
rigidbody.MovePosition(transform.position + Vector3.left* movePower * Time.deltaTime);
}
if(Input.GetKey(KeyCode.RightArrow))
{
rigidbody.MovePosition(transform.position + Vector3.right* movePower * Time.deltaTime);
}
if(Input.GetKey(KeyCode.DownArrow))
{
rigidbody.MovePosition(transform.position + Vector3.down* movePower * Time.deltaTime);
}
if(Input.GetKey(KeyCode.UpArrow))
{
rigidbody.MovePosition(transform.position + Vector3.up* movePower * Time.deltaTime);
}
}
The simplest way is to remove the Rigidbody from all cubes as they are supposed to be fixed. Another way is to mark the cubes' Rigidbody components as Kinematic, but this meant to be used for moving objects like player characters that should participate in physics but should not be moved by the engine.
I recommend reading the Unity Physics man page.
Update:
More things to consider:
Don't check Is Trigger
Check that your Layer Collision Matrix is set up right (menu Edit/Project Settings/Physics)
If the velocity is pretty high, physics engine might get confused and collision are not detected
Ensure that the models are not scaled down or up extremely (best is to have scale = 1)
The best mass for Rigidbody.mass is 1
Be careful when playing with PhysicsManager settings like Min Penetration For Penalty or Solver Iteration Count
Use gravity if possible
Never move by manipulating Transform directly. Use Rigidbody methods instead
Avoid calling rigidbody.MovePosition on every update if it's a constant linear motion. Do it once and leave it untouched
Remember to use FixedUpdate for calling rigidbody.MovePosition etc.
I'm having trouble with physics in unity 3d. I'm wanting my ball to bounce off of walls and go another direction. When the ball hits the wall it just bounces straight back. I have tried changing the direction to be orthogonal to the direction it hits the wall but it doesn't change direction. Due to this, the ball just keeps hitting the wall and bouncing straight back.
Secondly, sometimes the ball goes through the wall. The walls have box colliders while the ball has a sphere collider. They all have continuous dynamic as the collision detection mode.
Here's a link to a similar thread:
http://forum.unity3d.com/threads/22063-I-shot-an-arrow-up-in-the-air...?highlight=shooting+arrow
Personally, I would code the rotation using LookAt as GargarathSunman suggests in this link, but if you want to do it with physics, you'll probably need to build the javelin in at least a couple of parts, as the others suggest in the link, and add different drag and angular drag values to each part,perhaps density as well. If you threw a javelin in a vacuum, it would never land point down because air drag plays such an important part (all things fall at the same rate regardless of mass, thank you Sir Isaac Newton). It's a difficult simulation for the physics engine to get right.
Maybe try to get the collider point between your sphere and your wall then catch your rigidbody velocity and revert it by the collision point normal.
an example of a script to do that ---> (put this script on a wall with collider )
C# script:
public class WallBumper : MonoBehaviour
{
private Vector3 _revertDirection;
public int speedReflectionVector = 2;
/***********************************************
* name : OnCollisionEnter
* return type : void
* Make every gameObject with a RigidBody bounce againt this platform
* ********************************************/
void OnCollisionEnter(Collision e)
{
ContactPoint cp = e.contacts[0];
_revertDirection = Vector3.Reflect(e.rigidbody.velocity, cp.normal * -1);
e.rigidbody.velocity = (_revertDirection.normalized * speedReflectionVector);
}
}
I recently has an issue with a rocket going through targets due to speed and even with continuous dynamic collision detection I couldn't keep this from happening a lot.
I solved this using a script "DontGoThroughThings" posted in wiki.unity3d.com. This uses raycasting between current and previous positions and then ensures the frame ends with the colliders connected for messages an OnTrigger event. Has worked everytime since and it's just a matter of attaching the script so super easy to use.
I think the physics answer is as others have suggested to use multiple components with different drag although typically I think you only want a single RigidBody on the parent. Instead of direction using transform.LookAt you could try and calculate using Quaternion.LookRotation from the rigidbody.velocity. Then use Vector3.Angle to find out how much are are off. The greater the angle diference the more force should be experienced and then use RigidBody.ApplyTorque. Maybe use the Sin(angleDifference) * a constant so less force is applied to torque as you approach proper rotation.
Here is some code I used on my rocket although you'll have to substitute some things as I was pointing toward a fixed target and you'll want to use your velocity.
var rotationDirection = Quaternion.LookRotation(lockedTarget.transform.position - this.transform.position);
var anglesToGo = Vector3.Angle(this.transform.rotation.eulerAngles, rotationDirection.eulerAngles);
if (anglesToGo > RotationVelocity)
{
var rotationDirectionToMake = (rotationDirection * Quaternion.Inverse(this.transform.rotation)).eulerAngles.normalized * RotationVelocity;
transform.Rotate(rotationDirectionToMake);
}