I have a problem in pausing a sprite kit game with physics. The game contains a ball which moves in the SpriteScene and has the following parameters:
self.ball.physicsBody.friction = 0;
self.ball.physicsBody.linearDamping = 0;
self.ball.physicsBody.restitution = 1.0f;
self.ball.physicsBody.affectedByGravity = NO;
self.ball.physicsBody.usesPreciseCollisionDetection = YES;
The problem is that when I pause the game, I call these methods:
self.scene.physicsWorld.speed = 0;
self.ball_velocity = self.ball.physicsBody.velocity;
self.ball.physicsBody.velocity = CGVectorMake(0, 0);
self.ball.speed = 0;
self.ball.physicsBody.dynamic = NO;
[self.scene.view setPaused:YES];
and when resume, call these:
self.scene.physicsWorld.speed = 1;
self.ball.physicsBody.velocity = self.ball_velocity;
self.ball.physicsBody.dynamic = YES;
self.ball.speed = 1;
[self.scene.view setPaused:NO];
This stops the ball animation, but when resume, the ball position is changed and it seems if that was moving during the pause duration.
BTW, it works fine on iOS 8 but on iOS 9 it always fails.
Any suggestions ?!!
After chatting, we have come to the conclusion that between iOS8 and iOS9, Apple has done a change that pausing the scene now pauses the update loop. Since the update loop is being paused, the change in time is not being calculated correctly. What is now happening, is the change in time will be the time at unpause - the time at pause, simulating a lag state. The velocity will take the math into effect, and move objects based on this difference in time. To combat this issue, just make a parent node that will house all of your scenes's objects, and pause the parent. This will allow the update to still be called, thus allowing the change in time to stay consistent with the frame rate.