In my game I'm using Box2D to apply linear impulse to a circle object. When the impulse is applied to the object, it starts spinning clockwise but I can't get it to stop spinning.
Here is the code:
-(void) ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint touchLocation = [self convertTouchToNodeSpace:touch];
CGPoint vector = ccpSub(ccp(touchLocation.x,touchLocation.y), _ball.position);
b2Vec2 forceVector(vector.x / 5, vector.y / 5);
if ((vector.x <= 100) && (vector.y <= 100))
_ballBody->ApplyLinearImpulse(forceVector, _ballBody->GetLocalCenter());
}
Hope someone could clarify the situation.
UPD:
// Create ball body and shape
b2BodyDef ballBodyDef;
ballBodyDef.type = b2_dynamicBody;
ballBodyDef.position.Set(100/PTM_RATIO, 100/PTM_RATIO);
ballBodyDef.userData = _ball;
_ballBody = _world->CreateBody(&ballBodyDef);
b2CircleShape circle;
circle.m_radius = 26.0/PTM_RATIO;
b2FixtureDef ballShapeDef;
ballShapeDef.shape = &circle;
ballShapeDef.density = 0.3f;
ballShapeDef.friction = 0.2f;
ballShapeDef.restitution = 0.4f;
_ballBody->CreateFixture(&ballShapeDef);
use body->applyLinearImpulse(impulse, body->GetPosition())
Related
I am working on a game where the user can draw a line and a ball will bounce off of it but I have run into a problem where the line and the physics body don't line up. This is obviously a game breaking issue.
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
// Removes previous line
[lineNode removeFromParent];
CGPathRelease(pathToDraw);
UITouch* touch = [touches anyObject];
CGPoint positionInScene = [touch locationInNode:self];
pos1x = positionInScene.x;
pos1y = positionInScene.y;
NSLog(#"%d, %d", pos1x, pos1y);
}
- (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
// Removes previous line
[lineNode removeFromParent];
line.physicsBody = nil;
UITouch* touch = [touches anyObject];
CGPoint positionInScene = [touch locationInNode:self];
pathToDraw = CGPathCreateMutable();
CGPathMoveToPoint(pathToDraw, NULL, pos1x, pos1y);
lineNode = [SKShapeNode node];
lineNode.path = pathToDraw;
lineNode.strokeColor = [SKColor blackColor];
[self addChild:lineNode];
CGPathAddLineToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);
lineNode.path = pathToDraw;
int pos2x = positionInScene.x;
int pos2y = positionInScene.y;
SKSpriteNode* line = [[SKSpriteNode alloc] init];
line.name = lineCategoryName;
line.position = CGPointMake(pos1x, pos1y);
[self addChild:line];
line.physicsBody = [SKPhysicsBody bodyWithEdgeFromPoint:CGPointMake(pos1x, pos1y) toPoint:CGPointMake(pos2x, pos2y)];
line.physicsBody.restitution = 0.1f;
line.physicsBody.friction = 0.4f;
// make physicsBody static
line.physicsBody.dynamic = NO;
}
Thanks in advance!
Modify your code line:
line.physicsBody = [SKPhysicsBody bodyWithEdgeFromPoint:CGPointMake(pos1x, pos1y) toPoint:CGPointMake(pos2x, pos2y)];
to this:
line.physicsBody = [SKPhysicsBody bodyWithEdgeFromPoint:CGPointMake(0, 0) toPoint:CGPointMake(pos2x-line.position.x, pos2y-line.position.y)];
Your problem is that you are not taking into account that the line physical body's coordinates are relative to the view coordinates.
The documentation for bodyWithEdgeFromPoint:toPoint: clearly states that:
Parameters
p1
The starting point for the edge, relative to the owning node’s origin.
p2
The ending point for the edge, relative to the owning node’s origin.
In other words if your line starts at the screen coordinates of 30,30 and ends at 50,35 that translates to your physics body starting coordinates are 0,0 and ending coordinates are 20,5.
I have written a program that will rotate my imageView as i want (CW or ~CW).
And it is working fine.
but it is responding very slowly, I want it to respond quickly...
can you please help me out of it?
Thanks in advance...!
Following is my code------------------------
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch * touch = [[event allTouches]anyObject];
CGPoint prevLoc = [touch previousLocationInView:self];
CGPoint loc = [touch locationInView:self];
if (isRotating) {
float prevAngle = atan2(prevLoc.y-self.center.y,
prevLoc.x-self.center.x);
float newAngle = atan2( loc.y-self.center.y,
loc.x-self.center.x);
float finalAngle =angle+(newAngle-prevAngle);
//Apply new transform
CGAffineTransform rotateTransform = CGAffineTransformMakeRotation(Angle);
self.transform=rotateTransform;
angle = finalAngle;
}
}
I am developing 'Paper Toss' for iphone using cocos2d & I would like to know that how to implement 3D perspective view into this,because while we are throwing the paper ball to the bin,we have to get the 3D feel.I'am attaching the code which i have done,using this i have got a straight line motion.Please help me..
*- (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
// Choose one of the touches to work with
UITouch *touch = [touches anyObject];
CGPoint location = [touch locationInView:[touch view]];
location = [[CCDirector sharedDirector] convertToGL:location];
// Set up initial location of projectile
CGSize winSize = [[CCDirector sharedDirector] winSize];
CCSprite *projectile = [CCSprite spriteWithFile:#"ball.png"
rect:CGRectMake(0, 0, 40, 40)];
projectile.position = ccp(winSize.width/2,20);
// Determine offset of location to projectile
int offX = location.x - projectile.position.x;
int offY = location.y - projectile.position.y;
// Bail out if we are shooting down or backwards
if (offY <= 0) return;
// Ok to add now - we've double checked position
[self addChild:projectile];
// Determine where we wish to shoot the projectile to
int realY = winSize.height + (projectile.contentSize.width/2);
float ratio = (float) offX / (float) offY;
int realX = (realY * ratio) + projectile.position.x;
CGPoint realDest = ccp(realX, realY);
// Determine the length of how far we're shooting
int offRealX = realX + projectile.position.x;
int offRealY = realY + projectile.position.y;
float length = sqrtf((offRealX*offRealX)+(offRealY*offRealY));
float velocity = 480/1; // 480pixels/1sec
float realMoveDuration = length/velocity;
// Move projectile to actual endpoint
[projectile runAction:[CCSequence actions:
[CCMoveTo actionWithDuration:realMoveDuration position:realDest],
[CCCallFuncN actionWithTarget:self selector:#selector(spriteMoveFinished:)],
nil]];
//add to the projectiles array
projectile.tag = 2;
[_projectiles addObject:projectile];
}*
Finally I have completed paper toss using cocos2d.I implemented bezier curve and here it is,
// Bezier curve control points
bezier.controlPoint_1 = ccp(location.x-CONTROL_POINT1_X, CONTROL_POINT1_Y);
bezier.controlPoint_2 = ccp(location.x-CONTROL_POINT2_X, CONTROL_POINT2_Y);
bezier.endPosition = ccp(location.x-CONTROL_POINT1_X,distance);
// Motion along bezier curve and finally call a function
[projectile runAction:[CCSequence actions:
[CCAutoBezier actionWithDuration:DEFAULT_ACTION_DURATION bezier:bezier],
[CCCallFuncN actionWithTarget:self selector:#selector(collisionCheck:)], nil]];
Just scale your sprite image so it gets smaller the "further away" it is.
Hey you can use bezier curve for 3d perspective view in cocos2d.
bezier.controlPoint_1 = ccp(location.x-CONTROL_POINT1_X, CONTROL_POINT1_Y);
bezier.controlPoint_2 = ccp(location.x-CONTROL_POINT2_X, CONTROL_POINT2_Y);
i wanted to apply impulse when i release my finger but however i couldn't get it to work. the object body will not re-act to my input. so here's my code for release.
- (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
if (mouseJoint != nil) return;
UITouch *myTouch = [touches anyObject];
CGPoint location = [myTouch locationInView:[myTouch view]];
location = [[CCDirector sharedDirector] convertToGL:location];
b2Vec2 locationWorld = b2Vec2(location.x/PTM_RATIO, location.y/PTM_RATIO);
float distanceX = location.x-170;
float distanceY =location.y-270;
float distance = sqrtf(distanceX*distanceX+distanceY*distanceY);
CGFloat angle = atan2f(distanceY,distanceX);
// Apply an impulse to the body, using the angle
tailBody->ApplyLinearImpulse(b2Vec2(-distance*cosf(angle)/4+100,-distance*sinf(angle)/4+100), tailBody->GetPosition());
if (mouseJoint) {
world->DestroyJoint(mouseJoint);
mouseJoint = NULL;
}
}
is there something missing from the code?
I am wondering what is the best way to implement rotation-based dragging movements in my iPhone application.
I have a UIView that I wish to rotate around its centre, when the users finger is touch the view and they move it. Think of it like a dial that needs to be adjusted with the finger.
The basic question comes down to:
1) Should I remember the initial angle and transform when touchesBegan is called, and then every time touchesMoved is called apply a new transform to the view based on the current position of the finger, e.g., something like:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self]; //current position of touch
if (([touch view] == self)
&& [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS //middle is centre of view
&& [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //will be rotation gesture
//remember state of view at beginning of touch
CGPoint top = CGPointMake(self.middle.x, 0);
self.initialTouch = currentPoint;
self.initialAngle = angleBetweenLines(self.middle, top, self.middle, currentPoint);
self.initialTransform = self.transform;
}
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self]; //current position of touch
if (([touch view] == self)
&& [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS
&& [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //a rotation gesture
//rotate tile
float newAngle = angleBetweenLines(self.middle, CGPointMake(self.middle.x, 0), self.middle, currentPoint); //touch angle
float angleDif = newAngle - self.initialAngle; //work out dif between angle at beginning of touch and now.
CGAffineTransform newTransform = CGAffineTransformRotate(self.initialTransform, angleDif); //create new transform
self.transform = newTransform; //apply transform.
}
OR
2) Should I simply remember the last known position/angle, and rotate the view based on the difference in angle between that and now, e.g.,:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self]; //current position of touch
if (([touch view] == self)
&& [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS
&& [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //will be rotation gesture
//remember state of view at beginning of touch
CGPoint top = CGPointMake(self.middle.x, 0);
self.lastTouch = currentPoint;
self.lastAngle = angleBetweenLines(self.middle, top, self.middle, currentPoint);
}
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self]; //current position of touch
if (([touch view] == self)
&& [Utility getDistance:currentPoint toPoint:middle] <= ROTATE_RADIUS
&& [Utility getDistance:currentPoint toPoint:middle] >= MOVE_RADIUS) { //a rotation gesture
//rotate tile
float newAngle = angleBetweenLines(self.middle, CGPointMake(self.middle.x, 0), self.middle, currentPoint); //touch angle
float angleDif = newAngle - self.lastAngle; //work out dif between angle at beginning of touch and now.
CGAffineTransform newTransform = CGAffineTransformRotate(self.transform, angleDif); //create new transform
self.transform = newTransform; //apply transform.
self.lastTouch = currentPoint;
self.lastAngle = newAngle;
}
The second option makes more sense to me, but it is not giving very pleasing results (jaggy updates and non-smooth rotations). Which way is best (if any), in terms of performance?
Cheers!
It is actually much simpler than what you have tried.
You need three data points:
The origin of your view.
The location of the current touch
The location of the previous touch
The Touch object passed to you actually contains the last touch location. So you don't need to keep track of it.
All you have to do is calculate the angle between two lines:
Origin to Current Touch
Origin to Previous Touch
Then convert that to radians and use that in your CGAffineTransformRotate(). Do that all in your touchesMoved handler.
Here is a function to calculate what you need just that:
static inline CGFloat angleBetweenLinesInRadians(CGPoint line1Start, CGPoint line1End, CGPoint line2Start, CGPoint line2End) {
CGFloat a = line1End.x - line1Start.x;
CGFloat b = line1End.y - line1Start.y;
CGFloat c = line2End.x - line2Start.x;
CGFloat d = line2End.y - line2Start.y;
CGFloat line1Slope = (line1End.y - line1Start.y) / (line1End.x - line1Start.x);
CGFloat line2Slope = (line2End.y - line2Start.y) / (line2End.x - line2Start.x);
CGFloat degs = acosf(((a*c) + (b*d)) / ((sqrt(a*a + b*b)) * (sqrt(c*c + d*d))));
return (line2Slope > line1Slope) ? degs : -degs;
}
Courtesy of Jeff LaMarche at:
http://iphonedevelopment.blogspot.com/2009/12/better-two-finger-rotate-gesture.html
Example:
UITouch *touch = [touches anyObject];
CGPoint origin = [view center];
CGFloat angle = angleBetweenLinesInRadians(origin, [touch previousLocationInView:self.superview.superview], origin, [touch locationInView:self.superview.superview]);
Have you considered using UIRotationGestureRecognizer? Seems like that has the logic already baked in, and might make things simpler.