I am using addforce to throw object into the air, I want to instantiate a plane in position of landing point, how can I do that? I was thinking to calculate the landing point with Unity Physics API but I don't know how.
I have tried some code about projectiling but it won't help
if (other.tag == "CarPlayer")
{
other.gameObject.GetComponentInParent<Rigidbody>().AddForce(0, 1 * power, 1 * power, ForceMode.Impulse);
}
I really need an algorithm to find actual point that the object is going to land
As far as I know you're gonna have to do the math yourself; Unity doesn't have a built in instant simulation of this.
There are plenty of resources online on this already, this wiki-page on Trajectory Simulation for instance, which could probably help you.
If you need to calculate the force etc (the opposite of what you're asking), have a look at this blog, where the required trajectory is calculated. Source code
The simplest answer is probably to use something like this:
public Vector3 PlotTrajectoryAtTime (Vector3 start, Vector3 startVelocity, float time)
{
return (start) + (startVelocity * time) + (Physics.gravity * time * time * 0.5f);
}
(Before you start explaining PEMDAS; yes, I know the parentheses aren't needed, but I think the visual grouping gives better readability, thus easier understanding of it)
Related
Hey stackoverflow Community,
First of all:
I'm still very new about programming with C# and Unity.
My question:
I'm working on an idea for a Movement of a Cube.
It is planned that the cube will move forward by pressing a key (W-Key). But it shouldn't just move forward. It should jump forward to the next point. So always plus 1 of its axis into which it should go. Accordingly, it is only intended to go forward, right, down, left. He won't be able to jump over behind. You should also see that the cube jumps in the respective direction, so it should not teleport itself. :D
Does anyone have an idea how I can realize this movement?
I am very much looking forward to your ideas.
(Sorry if my English is not so good, my English not the best. ^^)
best regards
xKarToSx
So, in order to understand movement, it's best to first understand Vectors in Unity. Since you want to be moving the cube in the forward direction, I'm going to assume this is a 3D game, in which case you want to use a Vector3.
A Vector3 has three components: X, Y, and Z. Each component is tied to an axis. In simple terms, X is tied to left and right, Y is tied to up and down, and Z is tied to forward and back. So, Vector3 position = new Vector3(0, 1, 2); will be a vector that is 1 unit above and 2 units in front of the starting position.
Assuming you've attached this script to the cube you want to move, you can track its position with transform.position. So, if you want to move the cube one unit forward, your code would look something like this:
if(Input.GetKeyDown(KeyCode.W)) // This code will activate once the user presses W.
{
transform.position += new Vector3(0, 0, 1);
}
That will move the cube one unit forward in the Z direction. However, you don't want it to teleport, you want to see it move, correct? In that case, you want to check out Unity's Vector3.Lerp function. Basically, you would use it to smoothly transition an object between two defined positions. You'll need to implement a timer and a for loop in order to make this work correctly.
So, to summarize, for moving one unit forward in the Z direction, your code would look something like this:
if(Input.GetKeyDown(KeyCode.Z))
{
float startTime = Time.time; //Time.time is the current in-game time when this line is called. You'll want to save this to a variable
float speed = 1.0f; //The speed if something you'll want to define. The higher the speed, the faster the cube will move.
Vector3 startPosition = transform.position; //Save the starting position to a different variable so you can reference it later
Vector3 endPosition = startPosition + Vector3.forward; //Vector3.Forward is equivalent to saying (0, 0, 1);
float length = Vector3.Distance(startPosition, endPosition); //You'll need to know the total distance that the cube will move.
while(transform.position != endPosition) //This loop while keep running until the cube reaches its endpoint
{
float distCovered = (Time.time - startTime) * speed; //subtracting the current time from your start time and multiplying by speed will tell us how far the cube's moved
float fraction = distCovered / length; //This will tell us how far along the cube is in relation to the start and end points.
transform.position = Vector3.Lerp(startPosition, endPosition, fraction); //This line will smoothly transition between the start and end points
}
}
I hope this helps you. This is my first time answering a question so sorry if I got some things wrong/it's not the most optimized. Good Luck!
I am working on the friction for a square object for after it is done being pushed by the player. The block's movements are controlled purely through script using transform.Translate(velocity) each frame and only a boxcollider2D. I am speculating that because i am controlling the block's movements each frame manually is the reason i can't seem to get the boxcolliders2D's physics material 2D friction to work.
Basically, I am trying to recreate the built in physics similar to rigidbodies by using transform.translate, or use the built in physics if possible. So far, i've landed on something like this
newVelocity.x -= ( 1 / (newVelocity.x * newVelocity.x));
In an attempt to reduce the velocity.x each frame until it hits 0 and shorts out. Obviously, this falls apart when the velocity.x becomes a decimal number. I'm stumped on what i should be doing to achieve a friction similar to rigid bodies where it slows down a little at first and then much faster towards the end as it stops. Any and all help appreciated, thanks in advance!
You could compare the signs of the velocity before and after calculating the change in velocity, and set the velocity to zero when the sign changes, like so:
newVelocity.x -= ( 1 / (newVelocity.x * newVelocity.x));
if(Mathf.Sign(previousVelocity.x) != Mathf.Sign(newVelocity.x)) {
newVelocity.x = 0f;
}
One thing, though, is that normal friction is not calculated using the above equation, it's calculated as follows:
newVelocity.x -= frictionCoefficient*Time.fixedDeltaTime;
And with this, you wouldn't need to compare the velocity to the previous velocity as you can just say if the velocity is low, it's zero. You could still compare the previous velocity sign stuff if you wanted to though, but this is probably more efficient
if(newVelocity.x < 0.01f) {
newVelocty.x = 0f;
}
i try to to make an AI in C# (with unity) that can predict the estimated position of a moving object to hit it with a bullet
the moving object have a movement speed of 5f and the bullet have a speed of 7f
my problem is that the time my bullet travel to my estimated position my "enemy" already moved further and the bullet don't hit
do you know a formula or code that i can adapt to improve my targeting AI ? (already looking for that in google but don't find anything usefull)
thank
An answer to your question from unreal engine forums
Here is the top answer from there in case the link dies. I did not write this code I simply found it with a quick google of your problem which you stated you already tried.
Link answer:
Get the "velocity" of the target player. Multiply by the time the bullet will take to travel to the target. Then get the position of the target, add the velocity*time vector, and that's the position you should aim at. You can either hard-code the travel time (half a second, or whatever,) or you can in turn measure the distance between AI and player, and divide by bullet travel time, to come up with an approximate travel time. You can also apply a differential equation to calculate the exact time of impact and exact direction, but that requires a little more math and is slightly harder to write out, so I think the above will work best for you.
Simply:
Distance = Length(Target_Position - Firing_Position)
Time = Distance / Bullet_Speed
Predicted_Position = Target_Position + (Target_Velocity * Time)
I thought it would be simple as:
Vector3 point = Vector3.Transform(originalPoint, worldMatrix);
But apparently not... It make's the point's numbers shoot into the thousands.
Basically, what I'm trying to do is creating a collision system and every two points in this system is a line, so basically I want to collide lines. I want the lines to be able to scale, rotate, and translate based on a world matrix (so that the collision lines are in tune with the object's scale, rotation, and translation).
I've been trying for hours now and I can't seem to figure it out. I've tried multiplying by the View Matrix as well and while that is the closest to what I want, it seems to switching between two sets of numbers! It would be perfect if it stayed with the one set, I have no idea why it keeps changing...
Any help, please? :(
Edit: To add a little, I'm constantly updating the points in an Update call. But I don't know if that would change anything, either way the points = originalpoints first.
Steve H:
One line would have two points, so:
originalPoint[0] = new Vector3(-42.5f, 0f, 0f);
originalPoint[1] = new Vector3(42.5f, 0f, 0f);
point[0] = Vector3.Transform(originalPoint[0], worldMatrix);
point[1] = Vector3.Transform(originalPoint[1], worldMatrix);`
At first, point[0] & [1] equals the same as originalPoint[0] & [1]. But, the moment I move my player even just a few pixels...
point[0] = (-5782.5f, 0f, 0f)
point[1] = (-5697.5, 0f, 0f)
The player's position is -56.0f.
My worldMatrix goes as:
_world = Matrix.Identity // ISROT
* Matrix.CreateScale(_scale) // This object's scale
* Matrix.CreateFromQuaternion(_rotation) // It's rotation
* Matrix.CreateTranslation(_offset) // The offset from the centre
* Matrix.CreateFromQuaternion(_orbitRotation) // It's orbit around an object
* _orbitObjectWorld // The object to base this world from
* Matrix.CreateTranslation(_position); // This object's position
The objects display properly in graphics. They scale, rotate, translate completely fine. They follow the orbit's scale, rotation, and translation too but I haven't tested orbit much, yet.
I hope this is enough detail...
Edit: Upon further research, the original points are also being changed... :| I don't get why that's happening. They're the exact same as the new points...
I figured out my problem... -_-
So, after I create the line points, I do this at the end:
originalLines = collisionLines;
collisionLines & originalLines are both Vector3[] arrays.
I guess just by making one equal the other, it's like they're the exact same and changing one changes the other... that is something I did not know.
So I made this function:
void CreateOriginalPoints()
{
_originalPoints = new Vector3[_collisionPoints.Length];
for (int i = 0; i < _collisionPoints.Length; i++)
_originalPoints[i] = _collisionPoints[i];
}
And this solves the problem completely. It now makes complete sense to me why this problem was happening in the first place.
Thanks a lot Donnie & Steve H. I know you two didn't answer my question but it got me to poke around even deeper until I found the answer.
I am currently experimenting with some physics toys in XNA using the Farseer Physics library, however my question isn't specific to XNA or Farseer - but to any 2D physics library.
I would like to add "rocket"-like movement (I say rocket-like in the sense that it doesn't have to be a rocket - it could be a plane or a boat on the water or any number of similar situations) for certain objects in my 2D scene. I know how to implement this using a kinematic simulation, but I want to implement it using a dynamic simulation (i.e. applying forces over time). I'm sort of lost on how to implement this.
To simplify things, I don't need the dynamics to rotate the geometry, just to affect the velocity of the body. I'm using a circle geometry that is set to not rotate in Farseer, so I am only concerned with the velocity of the object.
I'm not even sure what the best abstraction should be. Conceptually, I have the direction the body is currently moving (unit vector), a direction I want it to go, and a value representing how fast I want it to change direction, while keeping speed relatively constant (small variations are acceptable).
I could use this abstraction directly, or use something like a "rudder" value which controls how fast the object changes directions (either clockwise or counter clockwise).
What kind of forces should I apply to the body to simulate the movement I'm looking for? Keep in mind that I would also like to be able to adjust the "thrust" of the rocket on the fly.
Edit:
The way I see it, and correct me if I'm wrong, you have two forces (ignoring the main thrust force for now):
1) You have a static "fin" that is always pointed in the same direction as the body. If the body rotates such that the fin is not aligned with the direction of movement, air resistance will apply forces to along the length of the fin, proportional to the angle between the direction of movement and the fin.
2) You have a "rudder", which can rotate freely within a specified range, which is attached some distance from the body's center of mass (in this case we have a circle). Again, when this plane is not parallel to the direction of movement, air resistance causes proportional forces along the length of the rudder.
My question is, differently stated, how do I calculate these proportional forces from air resistance against the fin and rudder?
Edit:
For reference, here is some code I wrote to test the accepted answer:
/// <summary>
/// The main entry point for the application.
/// </summary>
static void Main(string[] args)
{
float dc = 0.001f;
float lc = 0.025f;
float angle = MathHelper.ToRadians(45);
Vector2 vel = new Vector2(1, 0);
Vector2 pos = new Vector2(0, 0);
for (int i = 0; i < 200; i++)
{
Vector2 drag = vel * angle * dc;
Vector2 sideForce = angle * lc * vel;
//sideForce = new Vector2(sideForce.Y, -sideForce.X); // rotate 90 degrees CW
sideForce = new Vector2(-sideForce.Y, sideForce.X); // rotate 90 degrees CCW
vel = vel + (-drag) + sideForce;
pos = pos + vel;
if(i % 10 == 0)
System.Console.WriteLine("{0}\t{1}\t{2}", pos.X, pos.Y, vel.Length());
}
}
When you graph the output of this program, you'll see a nice smooth circular curve, which is exactly what I was looking for!
If you already have code to integrate force and mass to acceleration and velocity, then you just need to calculate the individual part of each of the two elements you're talking about.
Keeping it simple, I'd forget about the fin for a moment and just say that anytime the body of your rocket is at an angle to it's velocity, it will generate a linearly increasing side-force and drag. Just play around with the coefficients until it looks and feels how you want.
Drag = angle*drag_coefficient*velocity + base_drag
SideForce = angle*lift_coefficent*velocity
For the rudder, the effect generated is a moment, but unless your game absolutely needs to go into angular dynamics, the simpler thing to do is let the rudder control put in a fixed amount of change to your rocket body angle per time tick in your game.
I suddenly "get" it.
You want to simulate a rocket powered missile flying in air, OK. That's a different problem than the one I have detailed below, and imposes different limits. You need an aerospace geek. Or you could just punt.
To do it "right" (for space):
The simulated body should be provided with a moment of inertia around its center of mass, and must also have a pointing direction and an angular velocity. Then you compute the angular acceleration from the applied impulse and distance from the CoM, and add that to the angular velocity. This allows you to compute the current "pointing" of the craft (if you don't use gyros or paired attitude jets, you also get a (typically very small) linear acceleration).
To generate a turn, you point the craft off the current direction of movement and apply the main drive.
And if you are serious about this you also need to subtract the mass of burned fuel from the total mass and make the appropriate corrections to the moment of inertia at each time increment.
BTW--This may be more trouble than it is worth: maneuvering a rocket in free-fall is tricky (You may recall that the Russians bungled a docking maneuver at the ISS a few years ago; well, that's not because they are stupid.). Unless you tell us your use case we can't really advise you on that.
A little pseudocode to hint at what you're getting into here:
rocket {
float structuralMass;
float fuelMass;
point position;
point velocity;
float heading;
float omega; // Angular velocity
float structuralI; // moment of inertia from craft
float fuelI; // moemnt of inertia from the fuel load
float Mass(){return struturalMass + fuelMass};
float I(){return struturalI + fuelI};
float Thrust(float t);
float AdjustAttitude(float a);
}
The upshot is: maybe you want a "game physics" version.
For reason I won't both to go into here, the most efficient way to run a "real" rocket is generally not to make gradual turns and slow acceleration, but to push hard when ever you want to change direction. In this case you get the angle to thrust by subtracting the desired vector (full vector, not the unit) from the current one. Then you pointing in that direction, and trusting all out until the desired course is reached.
Imagine your in floating in empty space... And you have a big rock in your hand... If you throw the rock, a small impulse will be applied to you in the exact opposite direction you throw the rock. You can model your rocket as something that rapidly converts quantum's of fuel into some amount of force (a vector quantity) that you can add to your direction vector.