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Mac Steam prompts OSX graphics update

HardwareNews
, 19 Aug 2010News

Mac gamers got a massive boost when online gaming hub Steam started supporting the platform a few months ago.

The arrival of the online service, which allowed Mac-toting gamers to play the same games as their PC brethren, in some cases simultaneously, created a great deal of debate between the two camps, with the PC crowd pillorying Mac fans for the relatively poor performance of their expensive hardware.

Now it seems that Apple has got the message and has provided a graphics update for OS X Snow Leopard which will go some way towards closing the gap between the two platforms.

"When we launched Steam on Mac OS X back in May, there was a lot of buzz about performance, particularly relative to Windows running on the same machine," says a statement from Valve bosses. "While we met our goal of making sure all of our customers had an acceptable gaming experience at launch, we have spent a large chunk of effort in the intervening months working with Apple and their GPU vendors to close the performance gap with Windows."

Valve reckons a combination of changes to its own Steam code and the latest graphics update available from Apple today removes a variety of software bottlenecks, resulting in significant graphics performance enhancements for Mac gamers.

In addition to low-level implementation changes which have improved performance across the board, Apple has also removed some implementation inefficiencies which allow Steam to improve visual quality, most notably in the area of GPU occlusion queries.

Since the latest update to 10.6.4, Steam has been able to properly impliment 'occlusion query' which is a GPU-based mechanism which allows OpenGL to draw convincing lighting effects, particularly when a light source is obscured by in-game ojects.

"A given light source may be partly or wholly occluded by other geometry in the scene and we use the occlusion query to determine how occluded it is. The percentage of a given light source's screen area which is actually visible is used to scale the intensity of an additive glow sprite which is drawn over the frame without any z-buffering," waffled the techies from Steam.

Steam reckons the joint effort, which also includes improvements in the way the GPU deals with floating point calculations as well as unclogging a number of CPU bottlenecks, provides frame rate improvements anywhere between 15 and 120 per cent

Steam reckons that these latest improvements are just the beginning, with plenty of further tweaks on the cards (pun intended).

"We have been able to measure performance improvements with the latest software update, but we are anticipating even more speedups if Apple implements the uniform_buffer_object extension and GLSL 1.3 in a future update. With these additional features, we will be able to sidestep this particular CPU bottleneck, allowing us to win back a bunch of CPU time and, ultimately, performance."

The gaming outfit is reporting dramatic performance improvements on iMac (Late 2009 and Mid 2010), Mac mini (Early 2009 and Mid 2010), Mac Pro (Early 2009), MacBook (Early 2009 and Mid 2010) and MacBook Pro (15-inch, Mid 2010) and MacBook Pro (17-inch, Mid 2010) models. Older systems are generally already operating at the limits of the hardware, and Steam says it's unlikely that any significant performance improvements can be achieved in the future.

In conclusion, Steam said, "We're very excited about the performance improvements that Apple and the GPU vendors have been able to deliver this summer and we are working with them to further improve performance."

The Snow Leopard Graphics Update is detailed here and is available through Software Update under the Apple menu.

There are lots of juicy technical details from Steam here if that sort of thing gets your motor running.

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