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Tech Analysis: Half-Life 2 and Portal on Android

Digital Foundry goes hands-on with the Nvidia Shield Tegra 4 ports.

Just how far are we away from the day when we will be able to play games that reach last-gen console graphical quality on our mobile devices? From a technological standpoint, the arrival of chips like Tegra K1 and a fully featured Trine 2 port suggest that the time may be near. In the meanwhile, processors like Tegra 4 and PowerVR Rogue inch ever closer to the Xbox 360 and PlayStation 3 standard in terms of raw processing power. This makes the arrival of Nvidia-sanctioned Android ports of Half-Life 2 and Portal - out now on Google Play for $9.99/£5.99 - of remarkable interest.

The classic Half-Life 2 arrived in 2004, with Portal arriving almost three years later, both receiving decent enough - if not exactly exceptional - ports onto the Xbox 360 in 2008, and in the here and now we should be expecting great things from these titles running on Tegra 4, which remains one of the most capable mobile processors on the market. The games have been released with Nvidia Shield marketing in mind - the handheld having been slashed in price to a rather attractive $199 - but we strongly suspect the games will work on any Tegra 4-enabled device, though you may need a USB joypad.

We bought both games as soon as they were released, running them on Shield's console mode. This disables the in-built display, piping through video output via a mini-HDMI port, and ensuring that the full power of the chipset makes it through to the external display (mirroring both screens together causes bandwidth problems, and lowers frame-rates in demanding 3D games - something common to all tablets and smartphones we've tried this on).

First up, the bad news. Loading up Half-Life 2, we discover a game that is very much a stripped-down version of the PC original, bereft of the Lost Coast enhancements and running with the equivalent of what appear to be low settings. There's no anti-aliasing whatsoever, resolution is pared back to 600p, texture filtering is pretty hideous with no anisotropic support, while the lack of shadows in some areas can be quite disconcerting.

Playing the game on a small, five-inch 720p Shield display reduces the disappointment of the image quality somewhat, as these issues are less visible on a smaller panel with high pixel density, but we did expect better from the hardware. In a sense, we are reminded of how the game may have played on mid-level hardware back in 2004 when it was originally released. One more positive element we should point out is that audio quality - often pared back substantially on mobile games - is refreshingly decent on both Half-Life 2 and Portal.

"Inconsistent frame-rates and some brutal graphical compromises impact the quality of the mobile Half-Life 2 experience."

Cover image for YouTube videoHalf-Life 2 Android Nvidia Tegra 4 Shield Frame-Rate Test
Frame-rate analysis of the 600p Half-Life 2 reveals a less than stellar conversion of the Valve classic - YouTube decimating the 60Hz output to 30fps actually makes the game look more consistent than it is in real life.

Half-Life 2 frame-rates are also disappointing, as you can see from the analysis video - in common with many Android games, Half-Life 2 runs completely unlocked, with anything from 20fps to 60fps action depending on the complexity of the scene. Most of the time the game runs north of 30fps, which sounds great in theory, but keep an eye on frame-time - here we see a frequent lurching between 16ms, 33ms and 50ms updates, producing a highly inconsistent, juddering effect. The end result is a game that doesn't feel particularly good to control - even though the actual hardware end is well taken care of owing to the excellent Shield pad design. We also note occasional fleeting freezing issues, characterised by split-second repeat audio.

On the positive side, Half-Life 2's brilliant game design still holds up. Hailing from an era where iron sights weren't a first-person shooter standard, where regenerative health was confined to leaning against a wall in The Getaway, and where a single-player game wasn't called a "campaign", the fact is that Half-Life 2 still works, playing well by today's standards. It's just that in this case, the quality of the gameplay is seemingly held back by the platform it's running on. But it is still recognisably Half-Life 2, and in many ways proof-positive that true gaming class doesn't age.

This is also borne out by Portal. All of the graphical compromises we saw in Half-Life 2 appear to be much the same, but the somewhat stark level design combined with the simpler layout produces a look that feels a lot more true to the original game, especially when played on the smaller screen. There are still the same jarring dips in game fluidity - especially evident when you open a portal into a more complex area - but the fact that the action is generally a lot more sedate than Half-Life 2 and that frame-rates are generally higher ensures that this port hangs together a lot more effectively.

"Portal relies less on graphical loveliness, while the gameplay is less impacted by the inconsistent frame-rate."

Cover image for YouTube videoPortal Android Nvidia Tegra 4 Shield Frame-Rate Test
Portal is a pretty short game so there are questions about value, but of the two Valve conversions for Android this is the more successful end-product.

Overall then, a mixed bag. On the one hand, we expected Tegra 4 to handle these games more adeptly than the end results seen here, which lag significantly behind the standards set by last-gen consoles in 2008. We gave Half-Life 2 and Portal a go on an Intel Bay Trail based system (essentially revised Atom architecture with a pared-back Intel HD 4000 implementation - used primarily on tablets) running native Windows 8, and while we found ourselves GPU-bound pretty quickly on Half-Life 2, there's no doubt that we could run the game with similar performance levels at higher settings - and at 720p to boot. With Portal, we could even hit 720p60 with high settings.

So, can current mobile hardware run old PC games? The Bay Trail tests suggest that we should be able to, and while Tegra 4 may not hit last-gen console standards it is still a capable mobile part, so we do wonder why the quality of the games isn't better. Admittedly, we have little idea of the games' provenance. Comments from Valve's Doug Lombardi suggest that Nvidia handled the game itself, but it's not a company that tends to develop full-blown games, or indeed port others' work, so we wouldn't be surprised if the conversions were carried out by a third-party developer.

In the final analysis, these releases are indeed full-content replicas of the Valve classics, but seem to lack the care and attention to make them must-have mobile purchases - especially at what is a premium price point for an Android product. It's all the more surprising because, in theory, this would be one of the few Android titles where the developer could concentrate optimisation on a single platform - Shield.

Of the two, Half-Life 2 is the game we really wanted to be special, but the feel of a quality FPS relies upon a consistency in update and input latency that isn't really here, while the graphical downgrades can be brutal. The general style of gameplay and the less arduous technical requirements make Portal the better experience - but $9.99/£5.99 still feels too expensive for what is a fairly short game. In the meantime, we can't help but wonder whether enhanced versions for the much more capable Tegra K1 are in the works. This week, our favourite Chinese Android maker, Xiaomi, revealed the MiPad - effectively a Retina iPad Mini competitor based on the K1. Benchmarks suggest a 2x performance boost compared to Apple's A8, suggesting that the mobile graphics may finally compete with the last-gen console standard...