As you can see it, is the radius of the circle that determines how far away from the center the asteroid is placed. So, given the angle and the radius, you can derive the x- and y-positions using the cosine and sine, respectively:. As the angle increases from 0 to , find the angle on the horizontal axis in the plots for the cosine and sine waves. The vertical axis then tells you what the values for x and y are:. Make sense? Did you also notice that the curves of the sine and cosine are very similar?
In fact, the cosine wave is simply the sine wave shifted by 90 degrees. Go ahead and impress your friends and family with your knowledge of the mathematical origins of sine and cosine. Build and run the app. You should now have an asteroid that perpetually circles the enemy cannon. You can also make the asteroid spin around its own axis. Add the following line to the bottom of updateOrbiter :.
Remove the minus sign to give the asteroid extra spin that you can see. Pick whichever effect you like best. Build and run to play around with it for a bit. If the missile comes too close, the asteroid will destroy it before it gets a chance to do any damage to the cannon.
Add the following at the bottom of updateOrbiter :. No surprises for you here. Just remember to stop the CCMoveTo action that is on the missile sprite. For added visual effect, you also scale the asteroid sprite momentarily. There is still more that you can do with sines and cosines. A good place to show an example of such an animation is the game over screen. Add a few new instance variables in the implementation block at the top of HelloWorldLayer. Build and run, then try it out. Shoot at the cannon or collide your ship with it until one of you runs out of hit points.
The screen will fade to black and the game over text will appear:. The game no longer responds to the accelerometer, but the animations still keep going. That gives it a nice twist!
This is all fine and dandy, but where are the sine and cosines? As you may have noticed, the fade in animation of the black layer was very linear. It just goes from transparent to opaque in a conventional fashion. You can be better than conventional — you can use sinf to subtly change the timing.
It takes two seconds to fade in the black layer DarkenDuration. The variable t determines how much of that duration has passed by. It always has a value between 0. This converts t from a linear interpolation into one that breathes a bit more life into things:. The effect is subtle, but it's there. Now you know how it works. Inside that else clause in checkGameOver , add the following so that the method looks like so:.
If you take the absolute value of cosf — using fabsf — then the section that would previously go below zero is flipped. Because the output of these functions lies between 0.
The factor 3. You can tinker with these values until you have something that you think looks cool. These cosines are useful for all sorts of things! One last thing you can do is let the bouncing motion lose height over time.
You do this by adding a damping factor. Create a new instance variable in the HelloWorldLayer implementation block:. Do this at the beginning of the if block, like so:. Build and run, then try it out! Here is the full example project from this Trigonometry for Game Programming tutorial series.
Congratulations, you have peered even deeper into the true natures of sine, cosine and tangent, and you have tried them out to see some examples of how they're useful in a real game.
Tetrad 30k 12 12 gold badges 92 92 silver badges bronze badges. But Jari Komppa has already given basically the same answer as of now. Add a comment. Active Oldest Votes. Improve this answer. Jari Komppa Jari Komppa 7, 3 3 gold badges 28 28 silver badges 61 61 bronze badges. But I suppose in obj-c method calls works the same, without any explicit virtual keyword. Just add a note to make it clear that it should be called from within the baseclass update.
Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Making Agile work for data science. Viewed times. Thanks in advance. Martin 3, 5 5 gold badges 39 39 silver badges 64 64 bronze badges.
Nies Nies 25 7 7 bronze badges. That is Add a comment. Active Oldest Votes. The ccTime type represents time in seconds.
But you'll usually receive values in the millisecond range, like 0. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.
0コメント