When you start a normal iPhone app on the iPad, the pixels are just scaled up, creating a blurry output. That is the case even when you created the app with HD textures for the retina display of iPhone4.
For "Go Usagi", I already helped Durrza change that for iOS 3.2: When you start the game on the iPad, it looks just like the retina version scaled up full-screen, with crisp and sharp textures. In iOS 3.2, however, it was a bit of a hack to accomplish that. Now, with iOS 4.2 finally available for the iPad, it was simple to add that feature to the Sparrow core.
If you grab the latest development version via SVN, you can see the feature in action in the demo application. If you want to have your games behave the same way, you just have to add the following code to you application delegate:
[SPStage setSupportHighResolutions:YES]; // that one's just like before
// force high resolution if we're on the iPad:
if ([[UIDevice currentDevice].model rangeOfString:@"iPad"].location == 0)
On iOS 3.2 and non-retina devices, this code won't do anything. On the iPad with iOS 4.2, however, it will let your game run in high definition.
The only downside is that this code doesn't check if it runs in the simulator. The "model" property always returns "iPhone simulator". But on a real device, it will work fine =)
Take care, though: the iPad (revision 1) has only half the RAM of the iPhone4! So you'll have to take care that the HD textures fit into that space.
If anyone wants to test this feature, please be sure to come back here and post the results. Thanks in advance!