Rotations - success and frustration

re: implosion multitouch...

I had some success last night writing code to rotate the Selector with two-finger rotations. By playing around with the sio2->_SIO2window->n_touch variable in "templateScreenTap()", I could sense multitouch events. I used an algorithm to compare the angle between the two touches and compare it to the angle between the previous two touches to find a delta rotation and rotate the object by that much. If there were two fingers on the screen, things would rotate. If only one was on the screen, it would twist. After a bit of futzing around, it worked great.

At least in the simulator. (Using the option key to simulate multi-touch)

I figured it was about time to try this in the actual iPad, and I realize now that it is more complicated. Even as I tried to rotate the Selector, it would also move about - sometimes skipping between one location and the other. I think that this is a response to the iPads' sensors being a bit more "messy" than the simulator would have us believe! Specifically, I wonder if I am getting some flicker - when I have two fingers on the screen, perhaps the iPad is occasionally only detecting one.

I've also done a bit of exploring and found that the "templateScreenTap()" and "templateScreenMove()" methods in the template.mm file are just relaying the message from the EAGLView.mm file, and that gives me more information about how that works. The "_state" variable in templateScreenTap, for instance, indicates whether the "tap" was a touch or release event, and it seems to me that n_touch is indicating how many fingers changed touch/release state, not how many are remaining on the screen. Likewise, in the templateScreenMove(), the touches it receives are indicating only the ones that have moved, not a comprehensive list of touch points - and the n_touch variable corresponds to how many have moved, not how many there are. 

This changes my understanding considerably. Even as I wrote this last paragraph, I realize that my assumption that "flicker" was happening (in the previous paragraph) is likely wrong - I was just moving one finger and that caused the problem.

This will require a rethink about how I implement rotation.... For one thing, at the moment, I have been splitting responsibility for managing these touches between template.mm and GameManager - I need to reconsider that split.