John Carmack On RAGE For iOS/Android

Andrew Smith writes "John Carmack has an article up on the Bethesda blog discussing the iPhone/iPad version of RAGE, which is said to run at an impressive 60fps. 'Managing over a gig of media made dealing with flash memory IO and process memory management very important, and I did a lot of performance investigations to figure things out. Critically, almost all of the data is static, and can be freely discarded. iOS does not have a swapfile, so if you use too much dynamic memory, the OS gives you a warning or two, then kills your process. The bane of iOS developers is that "too much" is not defined, and in fact varies based on what other apps (Safari, Mail, iPod, etc) that are in memory have done. If you read all your game data into memory, the OS can’t do anything with it, and you are in danger. However, if all of your data is in a read-only memory mapped file, the OS can throw it out at will.' And a tweet by Carmack yesterday suggests that an Android version of RAGE is on the way too."

60fps on a phone? Why?

[Luckyo]

To break down the question: Why do we need this much fps in a game on a ~4 inch screen?

To understand the importance of the question, we need to understand how human eye works, and how it processes images.
Essentially, we have two kinds of cells in our eye capable of sensing light. One is capable of sensing shades of gray, and other senses a certain color (there are three different cells in this category, sensing different light wavelengths). Notably, cells sensing shades of gray can track many more image changes/second then those sensing colors due to their original purpose - tracking movement (for hunter-prey scenarios). Another thing to note is that while focus of our vision, the area that covers a very small center zone of our field of view houses vast majority of the cells that can sense colors, most of the gray-sensing cells are housed outside focus, in area of peripheral vision.

As a result, when you play a game on a large screen at home, a large portion of the screen's image is sensed by the area out of focus, and when your frame per second counter is below 60ish, the out-of-focus area begins to see separate images, while your focus still sees the flowing animation. This is what causes the uncomfortable discrepancy during high motion scenes when viewer still sees the fluid animation in his focus, but his peripheral vision doesn't, making the image look "choppy".

Now, enter mobile phones. The screen is actually small enough to mostly, if not entirely fit into our focus. This drastically cuts the need for high fps.

So why is Carmack talking about 60 fps on a graphics engine designed for phones? Is he actually clueless about the issue, is it marketing speak, or does he simply want to advertise to developers who may not be as familiar with the issue as he himself is?

Re:60fps on a phone? Why?

[Narishma]

They're not in that market anymore. They do not want to license (and support) their new engines.

Re:60fps on a phone? Why?

[NoSig]

Let's go with your stated finger-lag of 1/30 second. For an insanely fast game, it will display a reaction to that on the next frame, which at 30 fps can be 1/30 second later. So the total lag is 2/30, which is double of the lag in the real world. If you run at 60 fps, the total lag will instead be 1/30 finger lag plus 1/60 game lag, for a total of 3/60, which is 1/60 less than before. There is no physical impossibility in being able to detect a difference of 1/60 second. Now add to that that some games take, say, 4 frames to react, and then at 30 fps you get a lag of 5/30 second while at 60 fps you get a lag of 6/60, which is 4/60=1/15 second better. And yes, Rage isn't just a display engine, it's also doing path finding and so on at 60 fps.