I am porting a game over to a XNA 4.0 WP7 project but am having some problems with controls. I am using the accelerometer to control movement but sometimes the ship will completely skip to another area of the screen. I have the code below for the controls.
Accelerometer _motion;
Vector2 accelReading = new Vector2();
private float speed = 50.0f;
//Initialize
_motion = new Accelerometer();
_motion.ReadingChanged += new EventHandler<AccelerometerReadingEventArgs>(AccelerometerReadingChanged);
_motion.Start();
//Method for Changed Readings
public void AccelerometerReadingChanged(object sender, AccelerometerReadingEventArgs e)
{
accelReading.X = (float)e.X;
accelReading.Y = (float)e.Y;
vel.X = accelReading.Y * speed;
vel.Y = accelReading.X * speed;
}
//Update
float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;
pos += vel * elapsed;
vel *= 1 - elapsed;
ReadingChanged event is marked deprecated in WP 7.1 that's there was some reason and it might be reading errors use CurrentValueChanged.
If that do not help try WP7 using Motion class it is more accure
http://msdn.microsoft.com/en-us/library/microsoft.devices.sensors.motion(v=vs.92).aspx
Related
I'm working on an app which allows the user to rotate an object with iOS touch controls.
I have the following script working fine, with 1 issue that I can't seem to crack.
GameObject mainCamera;
public Camera camMain;
// One Touch Rotation
public float rotateSpeed = 0.5f;
static float pitch = 0.0f, yaw = 0.0f, zed = 0.0f, pitchBravo = 0.0f, yawBravo = 0.0f;
// Two Touch Zoom
public float perspectiveZoomSpeed = 0.1f;
// Three Touch Pan
public float panSpeed = 0.5f;
private float xAxis = 0.0f, yAxis = 0.0f;
private float xMain, yMain, zMain;
// Game Objects, Public or Private
private GameObject bravo;
void Update()
{
// Grabs Bravo
bravo = GameObject.Find ("bravo");
pitch = bravo.transform.eulerAngles.x;
yaw = bravo.transform.eulerAngles.y;
// One Touch controls rotation of Bravo
if (Input.touchCount == 1)
{
// Retrieves a single touch and names it TouchZero
Touch touchZero = Input.GetTouch (0);
// The start of the rotation will be aligned with Bravo's current rotation
//pitch = bravo.transform.eulerAngles.x;
//yaw = bravo.transform.eulerAngles.y;
// Times the difference in position of touch between frames by the rotation speed. deltaTime to keep movement consistent on all devices
pitch += touchZero.deltaPosition.y * rotateSpeed * Time.deltaTime;
yaw -= touchZero.deltaPosition.x * rotateSpeed * Time.deltaTime;
// Assigns the new eulerAngles to Bravo
bravo.transform.eulerAngles = new Vector3 (pitch, yaw, 0.0f);
}
// Two Touch contols the Field of View of the Camera aka. Zoom
if (Input.touchCount == 2)
{
mainCamera = GameObject.Find("main");
// Store both touches.
Touch touchZero = Input.GetTouch(0);
Touch touchOne = Input.GetTouch(1);
// Find the position in the previous frame of each touch.
Vector2 touchZeroPrevPos = touchZero.position - touchZero.deltaPosition;
Vector2 touchOnePrevPos = touchOne.position - touchOne.deltaPosition;
// Find the magnitude of the vector (the distance) between the touches in each frame.
float prevTouchDeltaMag = (touchZeroPrevPos - touchOnePrevPos).magnitude;
float touchDeltaMag = (touchZero.position - touchOne.position).magnitude;
// Find the difference in the distances between each frame.
float deltaMagnitudeDiff = prevTouchDeltaMag - touchDeltaMag;
// Otherwise change the field of view based on the change in distance between the touches.
camMain.fieldOfView += deltaMagnitudeDiff * perspectiveZoomSpeed;
// Clamp the field of view to make sure it's between 0 and 180.
camMain.fieldOfView = Mathf.Clamp(camMain.fieldOfView, 2.0f, 30.0f);
xAxis -= touchOne.deltaPosition.x * panSpeed * Time.deltaTime;
yAxis -= touchOne.deltaPosition.y * panSpeed * Time.deltaTime;
zMain = mainCamera.transform.position.z;
mainCamera.transform.position = new Vector3 (xAxis, yAxis, zMain);
}
}
With this script the object rotates left and right perfectly, 360°. But when the model is rotated up and down it gets to the 90° or -90° mark and bugs out, not allowing the user to carry on rotating.
I've done a bit of research and I believe it may have something to do with gimbal lock, my lack of knowledge on the subject means I haven't been able to come up with a fix.
Any help is appreciated.
GIF of bugged rotation
i have a question about moving a Box2D body to a specific position without using this for example.
body->SetTransform(targetVector,body->GetAngle())
I have some code which works for applyForce (here):
const float destinationControl = 0.3f;
b2Vec2 missilePosition = _physicalBody->GetPosition();
b2Vec2 diff = targetPosition - missilePosition;
float dist = diff.Length();
if (dist > 0)
{
// compute the aiming direction
b2Vec2 direction = b2Vec2(diff.x / dist, diff.y / dist);
// get the current missile velocity because we will apply a force to compensate this.
b2Vec2 currentVelocity = _physicalBody->GetLinearVelocity();
// the missile ideal velocity is the direction to the target multiplied by the max speed
b2Vec2 desireVelocity = b2Vec2(direction.x * maxSpeed, direction.y * maxSpeed);
// compensate the current missile velocity by the desired velocity, based on the control factor
b2Vec2 finalVelocity = control * (desireVelocity - currentVelocity);
// transform our velocity into an impulse (get rid of the time and mass factor)
float temp = (_physicalBody->GetMass() / normalDelta);
b2Vec2 finalForce = b2Vec2(finalVelocity.x * temp, finalVelocity.y * temp);
_physicalBody->ApplyForce(finalForce, _physicalBody->GetWorldCenter());
}
But the when the maxSpeed is to high the body move over the point to fast.
So does anyone know how to calculate a force (ApplyForce) or an impluse (ApplyLinearImpulse) to move the body to a target position (very exactly) in a specific time.
Or a solution with the code above. I mean calculate the maxSpeed to move the body in a specific time to the target position.
In my google search i found the interesting article from iforce about projected trajectory
(here). Maybe this could be help too?
Thank you in advance
I think you have it mostly correct, but you are not checking to see if the body will overshoot the target in the next time step. Here is what works for me:
b2Vec2 targetPosition = ...;
float targetSpeed = ...;
b2Vec2 direction = targetPosition - body->GetPosition();
float distanceToTravel = direction.Normalize();
// For most of the movement, the target speed is ok
float speedToUse = targetSpeed;
// Check if this speed will cause overshoot in the next time step.
// If so, we need to scale the speed down to just enough to reach
// the target point. (Assuming here a step length based on 60 fps)
float distancePerTimestep = speedToUse / 60.0f;
if ( distancePerTimestep > distanceToTravel )
speedToUse *= ( distanceToTravel / distancePerTimestep );
// The rest is pretty much what you had already:
b2Vec2 desiredVelocity = speedToUse * direction;
b2Vec2 changeInVelocity = desiredVelocity - body->GetLinearVelocity();
b2Vec2 force = body->GetMass() * 60.0f * changeInVelocity;
body->ApplyForce( force, body->GetWorldCenter(), true );
There is a way for single-time applied force to move by given distance (previous answer suggests that you can correct error in calculation by additional force in future frames):
public static void applyForceToMoveBy(float byX, float byY, Body body) {
force.set(byX, byY);
force.sub(body.getLinearVelocity());
float mass = body.getMass();
force.scl(mass * 30.45f);
body.applyForceToCenter(force, true);
}
Known limitations:
1) LinearVelocity effect was not tested;
2) calculation was tested with body linear damping = 0.5f. Appreciate, if somebody know how to add it into formula;
3) magic number 30.45f - maybe this could be fixed by point 2 or by world frame delta.
The only way I can think to do it is to check velocities for all physics bodies during every collisions.
- (BOOL)ccPhysicsCollisionBegin:(CCPhysicsCollisionPair *)pair piece:(CCNode *)pieceA piece:(CCNode *)pieceB{
float x = 0;
float y = 0;
for (int i = 0; i < [[_physicsWorld children] count]; i++) {
x = x + [[[_physicsWorld children][i] physicsBody] velocity].x;
y = y + [[[_physicsWorld children][i] physicsBody] velocity].y;
}
if ( x == 0 && y == 0 ) {
NSLog(#"stopped");
}
return YES;
}
This logs “stopped” multiple times when the scene first loads, then doesn’t log “stopped” again, even after physics bodies have clearly started moving and colliding and then come to a stop.
Ideally I'd like a delegate method that would notify me when all physics bodies have stopped moving, but I can't seem to find one.
FYI: I'm using the standard Chipmunk physics engine that's baked into Cocos2d V3.0
Chipmunk has a internal mechanism, which can, if activated, automatically deactivate physics bodies. My approach (I am using cocos2dx 3.11.1 and not -obj version with chipmunk 7.0.1) is:
activate the chipmunk idle mechanism (0.5 second - meaning, if an object is not moving for longer than 0.5 second it will be deactivated):
cpSpaceSetSleepTimeThreshold(space, 0.5f);
You do not need to use
cpSpaceSetIdleSpeedThreshold(space, <speed>);
because chipmunk calculates the threshold speed for you (according the gravitation used).
use this code for determination if all objects are not moving (static and kinetic bodies never sleep):
bool isAnyPhysicsBodyMoving(){
int i = 0; bool isMoving = false;
const Vector<PhysicsBody*>& bodies = getPhysicsWorld()->getAllBodies();
while( i < bodies.size() && !isMoving){
PhysicsBody *body = bodies.at(i);
isMoving = cpBodyGetType(body->getCPBody()) == CP_BODY_TYPE_DYNAMIC
&& !body->isResting();
i++;
}
return isMoving;
}
use static (and not kinetic) body for walls, in order to let objects sleep:
// wall
Size visibleSize = Director::getInstance()->getWinSize();
Vec2 origin = Director::getInstance()->getVisibleOrigin();
float border = 10.0f;
Size wallBodySize = Size(visibleSize.width+2*border, visibleSize.height+2*border);
PhysicsBody *wallBody = PhysicsBody::createEdgeBox(wallBodySize, PhysicsMaterial(1.0f, 1.0f, 0.5f), border);
Node* wall = Node::create();
wall->addComponent(wallBody);
wall->setAnchorPoint(Vec2(0.5f, 0.5f));
wall->setPosition(Point(visibleSize.width/2+origin.x, visibleSize.height/2+origin.y));
cpVect tt;
tt.x = wall->getPosition().x; tt.y = wall->getPosition().y;
//set position manually and BEFORE adding the object into the space
cpBodySetPosition(wallBody->getCPBody(), tt);
cpBodySetType(wallBody->getCPBody(), CP_BODY_TYPE_STATIC);
addChild(wall);
Any dynamic body connected to a kinetic body (for example laying on) will never sleep.
test it with DEBUG activated
getPhysicsWorld()->setDebugDrawMask(PhysicsWorld::DEBUGDRAW_ALL);
the boxes (their content) must become grey (=sleeping) and not red (=active):
In order to let it work, I have:
added an access method (to get cpSpace) in CCPhysicsWorld.h:
inline cpSpace* getSpace() const { return _cpSpace; }
Fix call of
cpBodySetTorque(body, 0.0f);`
in CCPhysicsBody.cpp to
if (body->t != 0.0f){
cpBodySetTorque(body, 0.0f);
}
Fix call of
cpBodySetPosition(_cpBody, tt);`
in CCPhysicsBody.cpp to
if (!cpveql(tt, cpBodyGetPosition(_cpBody))){
cpBodySetPosition(_cpBody, tt);
}
Steps 2. and 3. are necessary to avoid setting of the same physics body properties, which wake up a sleeping body.
The advantage of this approach is, that the chipmunk does not make any calculations for such physical bodies - saving CPU and battery.
I found something that works.
tl;dr
The basic idea is to keep track of the positions of the sprites myself, and then periodically check them to see if any of them have moved since they were last checked.
Longer version
I created a subclass of CCNode with the class name Piece.
These are my objects that are added to the physics world.
#implementation Piece {
float _previousX;
float _previousY;
}
-(void)updatePreviousScreenXandY{
_previousX = self.position.x;
_previousY = self.position.y;
}
-(BOOL)hasntMoved{
float currentX = self.position.x;
float currentY = self.position.y;
if ( currentX == _previousX && currentY == _previousY ) {
return TRUE;
}else{
return FALSE;
}
}
This is in my CCNode that acts as the game scene
-(void)doStuffAfterPiecesStopMoving:(NSTimer*)timer{
BOOL noPiecesHaveMoved = TRUE;
for (int i = 0; i < [[_physicsWorld children] count]; i++) {
if ( [[_physicsWorld children][i] hasntMoved] == FALSE ) {
noPiecesHaveMoved = FALSE;
break;
}
}
if ( noPiecesHaveMoved ) {
[timer invalidate];
NSLog(“Pieces have stopped moving”);
}else{
NSLog(“Pieces are still moving”);
[self updateAllPreviousPiecePositions];
}
}
-(void)updateAllPreviousPiecePositions{
for (int i=0; i < [[_physicsWorld children] count]; i++) {
Piece *piece = (Piece*)[_physicsWorld children][i];
[piece updatePreviousScreenXandY];
}
}
All I have to do is
[NSTimer scheduledTimerWithTimeInterval:TIME_BETWEEN_CHECKS
target:_gamePlay
selector:#selector(doStuffAfterPiecesStopMoving:)
userInfo:nil
repeats:YES];
and it’ll run whatever code I want after all Piece nodes have stopped moving.
The key to getting it to work well is to get the values for the Chipmunk space’s sleepTimeThreshold and the timer above’s time as low as possible.
My experimenting suggests the following settings work okay, but anything lower will cause problems (i.e. collisions not taking place properly):
sleepTimeThreshold = 0.15
my timer = 0.05
If anyone has a different/better solution or improvements to the above code, please post.
I'm trying to make my first game using Spritekit, so i have a sprite that i need to move around using my accelerometer. Well, no problem doing that; movement are really smooth and responsive, the problem is that when i try to rotate my sprite in order to get it facing its own movement often i got it "shaking" like he has parkinson. (:D)
i did realize that this happens when accelerometer data are too close to 0 on one of x, y axes.
So the question: Is there a fix for my pet parkinson?? :D
Here is some code:
-(void) update:(NSTimeInterval)currentTime{
static CGPoint oldVelocity;
//static CGFloat oldAngle;
if(_lastUpdatedTime) {
_dt = currentTime - _lastUpdatedTime;
} else {
_dt = 0;
}
_lastUpdatedTime = currentTime;
CGFloat updatedAccelX = self.motionManager.accelerometerData.acceleration.y;
CGFloat updatedAccelY = -self.motionManager.accelerometerData.acceleration.x+sinf(M_PI/4.0);
CGFloat angle = vectorAngle(CGPointMake(updatedAccelX, updatedAccelY));
_velocity = cartesianFromPolarCoordinate(MAX_MOVE_PER_SEC, angle);
if(oldVelocity.x != _velocity.x || oldVelocity.y != _velocity.y){
_sprite.physicsBody.velocity = CGVectorMake(0, 0);
[_sprite.physicsBody applyImpulse:CGVectorMake(_velocity.x*_sprite.physicsBody.mass, _velocity.y*_sprite.physicsBody.mass)];
_sprite.zRotation = vectorAngle(_velocity);
oldVelocity = _velocity;
}
}
static inline CGFloat vectorAngle(CGPoint v){
return atan2f(v.y, v.x);
}
i did try to launch the update of the _velocity vector only when updatedAccelX or updatedAccelY are, in absolute value >= of some values, but the result was that i got the movement not smooth, when changing direction if the value is between 0.1 and 0.2, and the problem wasn't disappearing when the value was under 0.1.
i would like to maintain direction responsive, but i also would like to fix this "shake" of the sprite rotation.
I'm sorry for my bad english, and thanks in advance for any advice.
You can try a low pass filter (cf. to isolate effect of gravity) or high pass filter (to isolate effects of user acceleration).
#define filteringFactor 0.1
- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
//low pass
accelerX = (acceleration.x * filteringFactor) + (accelerX * (1.0 - filteringFactor));
//idem … accelerY
//idem … accelerZ
//or high pass
accelerX = acceleration.x - ( (acceleration.x * filteringFactor) + (accelerX * (1.0 - filteringFactor)) );
//idem … accelerY
//idem … accelerZ
}
I've tried following the example on XNA Development website but when the character jumps, they cant be controlled/cant stop the jump movement until its completed.
How do I get around that? Here is my jump code
private void Jump()
{
if (mCurrentState != FoxState.Jumping)
{
mCurrentState = FoxState.Jumping;
mStartingPosition = Position;
Direction.Y = Fox_vSpeed;
Speed = new Vector2(Fox_Speed, Fox_Speed);
}
}
Gravity is simply a force that affects the acceleration of an object. Acceleration changes the velocity of an object so you can do just that: Speed -= Vector2.UnitY * -2; You can then check collision with an object on the ground and once such collision happens you can zero the Y component of Speed (and possibly incur damage on the poor fox if the Y component is too high in magnitude (absolute value)).
Something like:
Update(GameTime gt)
{
if(mCurrentState == FoxState.Jumping)
{
Speed -= Vector2.UnitY * -2;
Position += Speed;
if(Position.Y > GroundLevel)
{
Position.Y = 0;
mCurrentState = FoxState.Walking;
}
}
}
Modify your question with details if you need more information.