I am trying to position a body using the physics engine with this code:
float touchX = pp[0];
float touchY = pp[1];
float diffX = touchX - mBody.getPosition().x;
float diffY = touchY - mBody.getPosition().y;
mBody.setLinearVelocity(new Vector2(( pp[0]) / PhysicsConstants.PIXEL_TO_METER_RATIO_DEFAULT , ( pp[1]) / PhysicsConstants.PIXEL_TO_METER_RATIO_DEFAULT));
The X and Y coords are from a TMX tile map and are 32 pixels square, I am trying to get the body in the physics engine to move to certain tiles in a tile map (held in the pp[] array) but instead it moves to a random chaotic path. Is this the right approach to convert X,Y coords and move to that point??
Thanks
.setLinearVelocity doesn't move body to certain possition. To do this you need to use .setTransform
.setLinearVelocity is like you add force to the body and make it move, so it doesn't move to the position you want.
.setTransform is like you set the position of the body. So it doesn't move slowly from A to B, but disappears from A and suddenly appears at B
You can easy move it slowly by code yourself.
Related
This is a question for Unity people or Math geniuses.
I'm making a game where I have a circle object that I can move, but I don't want it to intersect or go into other (static) circles in the world (Physics system isn't good enough in Unity to simply use that, btw).
It's in 3D world, but the circles only ever move on 2 axis.
I was able to get this working perfectly if circle hits only 1 other circle, but not 2 or more.
FYI: All circles are the same size.
Here's my working formula for 1 circle to move it to the edge of the colliding circle if intersecting:
newPosition = PositionOfStaticCircleThatWasJustIntersected + ((positionCircleWasMovedTo - PositionOfStaticCircleThatWasJustIntersected).normalized * circleSize);
But I can't figure out a formula if the moving circle hits 2 (or more) static circles at the same time.
One of the things that confuse me the most is the direction issue depending on how all the circles are positioned and what direction the moving circle is coming from.
Here's an example image of what I'm trying to do.
Since we're operating in a 2D space, let's approach this with some geometry. Taking a close look at your desired outcome, a particular shape become apparent:
There's a triangle here! And since all circles are the same radius, we know even more: this is an isosceles triangle, where two sides are the same length. With that information in hand, the problem basically boils down to:
We know what d is, since it's the distance between the two circles being collided with. And we know what a is, since it's the radius of all the circles. With that information, we can figure out where to place the moved circle. We need to move it d/2 between the two circles (since the point will be equidistant between them), and h away from them.
Calculating the height h is straightforward, since this is a right-angle triangle. According to the Pythagorean theorem:
// a^2 + b^2 = c^2, or rewritten as:
// a = root(c^2 - b^2)
float h = Mathf.Sqrt(Mathf.Pow(2 * a, 2) - Mathf.Pow(d / 2, 2))
Now need to turn these scalar quantities into vectors within our game space. For the vector between the two circles, that's easy:
Vector3 betweenVector = circle2Position - circle1Position
But what about the height vector along the h direction? Well, since all movement is on 2D space, find a direction that your circles don't move along and use it to get the cross product (the perpendicular vector) with the betweenVector using Vector3.Cross(). For
example, if the circles only move laterally:
Vector3 heightVector = Vector3.Cross(betweenVector, Vector3.up)
Bringing this all together, you might have a method like:
Vector3 GetNewPosition(Vector3 movingCirclePosition, Vector3 circle1Position,
Vector3 circle2Position, float radius)
{
float halfDistance = Vector3.Distance(circle1Position, circle2Position) / 2;
float height = Mathf.Sqrt(Mathf.Pow(2 * radius, 2) - Mathf.Pow(halfDistance, 2));
Vector3 betweenVector = circle2Position - circle1Position;
Vector3 heightVector = Vector3.Cross(betweenVector, Vector3.up);
// Two possible positions, on either side of betweenVector
Vector3 candidatePosition1 = circle1Position
+ betweenVector.normalized * halfDistance
+ heightVector.normalized * height;
Vector3 candidatePosition2 = circle1Position
+ betweenVector.normalized * halfDistance
- heightVector.normalized * height;
// Absent any other information, the closer position will be assumed as correct
float distToCandidate1 = Vector3.Distance(movingCirclePosition, candidatePosition1);
float distToCandidate2 = Vector3.Distance(movingCirclePosition, candidatePosition2);
if (distToCandidate1 < distToCandidate2){
return candidatePosition1;
}
else{
return candidatePosition2;
}
}
Hi I have a question that I'm hoping someone can help me work through. I've asked elsewhere to no avail but it seems like a standard problem so I'm not sure why I haven't been getting answers.
Its basically setting up a zoom function that mirrors Google Maps zoom. Like, the camera zooms in/out onto where your mouse is. I know this probably gets asked a lot but I think Unity's new Input System changed things up a bit since the 4-6 year old questions that I've found in my own research.
In any case, I've set up an parent GameObject that holds all 2D sprites that will be in my scene and an orthographic camera. I can set the orthographic size through code to change to zoom, but its moving the camera to the proper place that I am having trouble with.
This was my 1st attempt:
public Zoom(float direction, Vector2 mousePosition) {
// zoom calcs
float rate 1 + direction * Time.deltaTime;
float targetOrtho = Mathf.MoveTowards(mainCam.orthographicSize, mainCam.orthoGraphicSize/rate, 0.1f);
// move calcs
mousePosition = mainCam.ScreenToWorldPoint(mousePosition);
Vector2 deltaPosition = previousPosition - mousePosition;
// move and zoom
transform.position += new Vector3(deltaPosition.x, deltaPosition.y, 0);
// zoomLevels are a generic struct that holds the max/min values.
SetZoomLevel(Mathf.Clamp(targetOrthoSize, zoomLevels.min, zoomLevels.max));
previousPosition = mousePosition;
}
This function gets called through my input controller, activated through Unity's Input System events. When the mouse wheel scrolls, the Zoom function is given a normalized value as direction (1 or -1) and the current mousePosition. When its finished its calculation, the mousePosition is stored in previousPosition.
The code actually works -- except it is extremely jittery. This, of course happens because there is no Time.deltaTime applied to the camera movement, nor is this in LateUpdate; both of which helps to smooth the movements. Except, in the former case, multiplying Time.deltaTime to new Vector3(deltaPosition.x, deltaPosition.y, 0) seems to cause the zoom occur at the camera's centre rather than the mouse position. When i put zoom into LateUpdate, it creates a cool but unwanted vibration effect when the camera moves.
So, after doing some thinking and reading, I thought it may be best to calculate the difference between the mouse position and the camera's center point, then multiply it by a scale factor, which is the camera's orthographic size * 2 (maybe...??). Hence my updated code here:
public void Zoom(float direction, Vector2 mousePosition)
{
// zoom
float rate = 1 + direction * Time.unscaledDeltaTime * zoomSpeed;
float orthoTarget = Mathf.MoveTowards(mainCam.orthographicSize, mainCam.orthographicSize * rate, maxZoomDelta);
SetZoomLevel(Mathf.Clamp(orthoTarget, zoomLevels.min, zoomLevels.max));
// movement
if (mainCam.orthographicSize < zoomLevels.max && mainCam.orthographicSize > zoomLevels.min)
{
mousePosition = mainCam.ScreenToWorldPoint(mousePosition);
Vector2 offset = (mousePosition - new Vector2(transform.position.x, transform.position.y)) / (mainCam.orthographicSize * 2);
// panPositions are the same generic struct holding min/max values
offset.x = Mathf.Clamp(offset.x, panPositions.min.x, panPositions.max.x);
offset.y = Mathf.Clamp(offset.y, panPositions.min.y, panPositions.max.y);
transform.position += new Vector3(offset.x, offset.y, 0) * Time.deltaTime;
}
}
This seems a little closer to what I'm trying to achieve but the camera still zooms in near its center point and zooms out on some point... I'm a bit lost as to what I am missing out here.
Is anyone able to help guide my thinking about what I need to do to create a smooth zoom in/out on the point where the mouse currently is? Much appreciated & thanks for reading through this.
Ok I figured it out for if anyone ever comes across the same problem. it is a standard problem that is easily solved once you know the math.
Basically, its a matter of scaling and translating the camera. You can do one or the other first - it does not matter; the outcome is the same. Imagine your screen looks like this:
The green box is your camera viewport, the arrow is your cursor. When you zoom in, the orthographic size gets smaller and shrinks around its anchor point (usually P1(0,0)). This is the scaling aspect of the problem and the following image explains it well:
So, now we want to move the camera position to the new position:
So how do we do this? Its just a matter of getting distance from the old camera position (P1(0, 0)) to the new camera position (P2(x,y)). Basically, we only want this:
My solution to find the length of the arrow in the picture above was to basically subtract the length of the cursor position from the old camera position (oldLength) from the length of the cursor position to the new camera position (newLength).
But how do you find newLength? Well, since we know the length will be scaled accordingly to the size of the camera viewport, newLength will be either oldLength / scaleFactor or oldLength * scaleFactor, depending on whether you want to zoom in or out, respectively. The scale factor can be whatever you want (zoom in/out by 2, 4, 1.4... whatever).
From there, its just a matter of subtracting newLength from oldLength and adding that difference from the current camera position. The psuedo code is below:
(Note that i changed 'newLength' to 'length' and 'oldLength' to 'scaledLength')
// make sure you're working in world space
mousePosition = camera.ScreenToWorldPoint(mousePosition);
length = mousePosition - currentCameraPosition;
scaledLength = length / scaleFactor // to zoom in, otherwise its length * scaleFactor
deltaLength = length - scaledLength;
// change position
cameraPosition = currentCameraPosition - deltaLength;
// do zoom
camera.orthographicSize /= scaleFactor // to zoom in, otherwise orthographic size *= scaleFactor
Works perfectly for me. Thanks to those who helped me in a discord coding community!
As per my game requirements, I was giving manual force when two cars collide with each other and move back.
So I want the correct code that can justify this. Here is the example, collision response that I want to get:
As per my understanding, I have written this code:
Vector3 reboundDirection = Vector3.Normalize(transform.position - other.transform.position);
reboundDirection.y = 0f;
int i = 0;
while (i < 3)
{
myRigidbody.AddForce(reboundDirection * 100f, ForceMode.Force);
appliedSpeed = speed * 0.5f;
yield return new WaitForFixedUpdate();
i++;
}
I am moving, my cars using this code:
//Move the player forward
appliedSpeed += Time.deltaTime * 7f;
appliedSpeed = Mathf.Min(appliedSpeed, speed);
myRigidbody.velocity = transform.forward * appliedSpeed;
Still, as per my observation, I was not getting, collision response in the proper direction. What is the correct way for getting above image reference collision response?
Until you clarify why you have use manual forces or how you handle forces generated by Unity Engine i would like to stress one problem in your approach. You calculate direction based on positions but positions are the center of your cars. Therefore, you are not getting a correct direction as you can see from the image below:
You calculate the direction between two pivot or center points therefore, your force is a bit tilted in left image. Instead of this you can use ContactPoint and then calculate the direction.
As more detailed information so that OP can understand what i said! In the above image you can see the region with blue rectangle. You will get all the contact points for the corresponding region using Collision.contacts
then calculate the center point or centroid like this
Vector3 centroid = new Vector3(0, 0, 0);
foreach (ContactPoint contact in col.contacts)
{
centroid += contact.point;
}
centroid = centroid / col.contacts.Length;
This is the center of the rectangle to find the direction you need to find its projection on your car like this:
Vector3 projection = gameObject.transform.position;
projection.x = centroid.x;
gameObject.GetComponent<Rigidbody>().AddForce((projection - centroid )*100, ForceMode.Impulse);
Since i do not know your set up i just got y and z values from car's position but x value from centroid therefore you get a straight blue line not an arrow tilted to left like in first image even in the case two of second image. I hope i am being clear.
I am trying to calculate circular motion (orbit) around an object. The code i have gives me a nice circular orbit around the object. The problem is that when i rotate the object, the orbit behaves as though the object were not rotated.
I've put a really simple diagram below to try and explain it better. The left is what i get when the cylinder is upright, the middle is what i currently get when the object is rotated. The image on the right is what i would like to happen.
float Gx = target.transform.position.x - ((Mathf.Cos(currentTvalue)) * (radius));
float Gz = target.transform.position.z - ((Mathf.Sin(currentTvalue)) * (radius));
float Gy = target.transform.position.y;
Gizmos.color = Color.green;
Gizmos.DrawWireSphere(new Vector3(Gx, Gy, Gz), 0.03f);
How can i get the orbit to change with the objects rotation? I have tried multiplying the orbit poisition "new Vector3(Gx,Gy,Gz)" by the rotation of the object:
Gizmos.DrawWireSphere(target.transform.rotation*new Vector3(Gx, Gy, Gz), 0.03f);
but that didn't seem to do anything?
That is happening because you are calculating the vector (Gx, Gy, Gz) in world space coordinates, where the target object's rotations are not taken in consideration.
One way to solve your needs is to calculate this rotation using the target object's local space coordinates, and then convert them to world space coordinates. This will correctly make your calculations consider the rotation of the target object.
float Gx = target.transform.localPosition.x - ((Mathf.Cos(currentTvalue)) * (radius));
float Gz = target.transform.localPosition.z - ((Mathf.Sin(currentTvalue)) * (radius));
float Gy = target.transform.localPosition.y;
Vector3 worldSpacePoint = target.transform.TransformPoint(Gx, Gy, Gz);
Gizmos.color = Color.green;
Gizmos.DrawWireSphere(worldSpacePoint, 0.03f);
Notice that instead of target.transform.position, which retrieves the world space coordinates of the given transform, I am doing the calculations using the target.transform.localPosition, which retrieves the local space coordinates of the given transform.
Also, I am calling the TransformPoint() method, which converts the coordinates which I have calculated in local space to its corresponding values in world space.
Then you might safely call the Gizmos.DrawWireSphere() method, which requires world space coordinates to work correctly.
I would like to use Cocos2d on the iPhone to draw a 2D car and make it steer from left to right in a natural way.
Here is what I tried:
Calculate the angle of the wheels and just move it to the destination point where the wheels point to. But this creates a very unnatural feel. The car drifts half the time
After that I started some research on how to get a turning circle from a car, which meant that I needed a couple of constants like wheelbase and the width of the car.
After a lot of research, I created the following code:
float steerAngle = 30; // in degrees
float speed = 20;
float carWidth = 1.8f; // as in 1.8 meters
float wheelBase = 3.5f; // as in 3.5 meters
float x = (wheelBase / abs(tan(steerAngle)) + carWidth/ 2);
float wheelBaseHalf = wheelBase / 2;
float r = (float) sqrt(x * x + wheelBaseHalf * wheelBaseHalf);
float theta = speed * 1 / r;
if (steerAngle < 0.0f)
theta = theta * -1;
drawCircle(CGPointMake(carPosition.x - r, carPosition.y),
r, CC_DEGREES_TO_RADIANS(180), 50, NO);
The first couple of lines are my constants. carPosition is of the type CGPoint. After that I try to draw a circle which shows the turning circle of my car, but the circle it draws is far too small. I can just make my constants bigger, to make the circle bigger, but then I would still need to know how to move my sprite on this circle.
I tried following a .NET tutorial I found on the subject, but I can't really completely convert it because it uses Matrixes, which aren't supported by Cocoa.
Can someone give me a couple of pointers on how to start this? I have been looking for example code, but I can't find any.
EDIT After the comments given below
I corrected my constants, my wheelBase is now 50 (the sprite is 50px high), my carWidth is 30 (the sprite is 30px in width).
But now I have the problem, that when my car does it's first 'tick', the rotation is correct (and also the placement), but after that the calculations seem wrong.
The middle of the turning circle is moved instead of kept at it's original position. What I need (I think) is that at each angle of the car I need to recalculate the original centre of the turning circle. I would think this is easy, because I have the radius and the turning angle, but I can't seem to figure out how to keep the car moving in a nice circle.
Any more pointers?
You have the right idea. The constants are the problem in this case. You need to specify wheelBase and carWidth in units that match your view size. For example, if the image of your car on the screen has a wheel base of 30 pixels, you would use 30 for the WheelBase variable.
This explains why your on-screen circles are too small. Cocoa is trying to draw circles for a tiny little car which is only 1.8 pixels wide!
Now, for the matter of moving your car along the circle:
The theta variable you calculate in the code above is a rotational speed, which is what you would use to move the car around the center point of that circle:
Let's assume that your speed variable is in pixels per second, to make the calculations easier. With that assumption in place, you would simply execute the following code once every second:
// calculate the new position of the car
newCarPosition.x = (carPosition.x - r) + r*cos(theta);
newCarPosition.y = carPosition.y + r*sin(theta);
// rotate the car appropriately (pseudo-code)
[car rotateByAngle:theta];
Note: I'm not sure what the correct method is to rotate your car's image, so I just used rotateByAngle: to get the point across. I hope it helps!
update (after comments):
I hadn't thought about the center of the turning circle moving with the car. The original code doesn't take into account the angle that the car is already rotated to. I would change it as follows:
...
if (steerAngle < 0.0f)
theta = theta * -1;
// calculate the center of the turning circle,
// taking int account the rotation of the car
circleCenter.x = carPosition.x - r*cos(carAngle);
circleCenter.y = carPosition.y + r*sin(carAngle);
// draw the turning circle
drawCircle(circleCenter, r, CC_DEGREES_TO_RADIANS(180), 50, NO);
// calculate the new position of the car
newCarPosition.x = circleCenter.x + r*cos(theta);
newCarPosition.y = circleCenter.y + r*sin(theta);
// rotate the car appropriately (pseudo-code)
[car rotateByAngle:theta];
carAngle = carAngle + theta;
This should keep the center of the turning circle at the appropriate point, even if the car has been rotated.