Far Cry 3 – Offloading graphical effects to the CPU, differences between PC and console builds

Rage3D’s member ‘Napoleonic’ has spotted an interesting PDF from Ubisoft’s Far Cry 3 GDC 2012 presentation. In this presentation, Ubisoft has highlighted the differences between the PC and the console builds of Far Cry 3, and revealed that some of the graphical effects will be offloaded to the CPU in order to save some additional GPU cycles.
Now as you may have guessed, this offload routine was implemented in order to optimize the game to consoles. It’s well known that current generation consoles cannot push great visuals unless developers offload a number of GPU instructions to the CPU (SPU for PS3). The problem here is that the PC version will most probably suffer from this particular console optimization.
Not only that, but given the console’s framerate target (30fps), Ubisoft might not optimize the PC version for older CPUs. Our guess is that they will, once again, rely on the additional raw power of current-generation CPUs to overcome their laziness, and that’s something really unacceptable. What’s even funnier here is that CPU requirements would be lower, provided there weren’t those console optimizations (and yes, even high-end CPUs would benefit from something like that).
Ubisoft will be also doing their best to keep the memory requirements to low levels, something that – once again – is due to console’s hardware. According to the GDC 2012 presentation, the world in Far Cry 3 is composed of maps, which are divided into sectors. Each sector is 64 by 64 metres and contains roughly 70 probes. Together with the 3D grid, that’s used for spatial indexing, this brings the memory consumption per sector to a little bit less than 15KB.
In total numbers, the game has a maximum of 51sectors around the player loaded in memory at any one time, so theoverall footprint in-game is around 760KB on consoles, and around 11.5Mb on PC.
Contrary to the console versions, the PC version will feature distant light sources – suchas the sun and the sky – and support for global illumination from dynamic lights. This is especially useful for night time scenes. Ubisoft also bakes local radiance transfer. Using that, the company can approximate global illumination from dynamic light sources with a technique called ‘bake local radiance transfer’.
Furthermore, Ubisoft has implemented a blur effect on the volume maps for the PC version in order to soften the irradiance, an effect that is not present on the console versions. This effect is said to give Ubisoft more gradient levels, especially with the occlusion caused by the vegetation.
Far Cry 3 is currently planned for a November 30th release on PC, X360 and PS3!