Question about DR on Intel + AMD

[KAKTUSDIGITAL]

A long time ago I remember the AMD machines output slightly different buckets to Intel machines. Has the engine which utilises the fpu in the cpu been changed in recent builds? (feel free to correct me) but mental ray uses a 'virtual fpu' which ensures everything pumped out of the machine will look identical regardless of chip platform, is Vray doing this in the same manner?

Cheers,
Henry

[vlado]

From what we've tested, SP2 produces pretty much identical output on Intel and AMD machines.

Note however that this is only as far as V-Ray itself goes. Other rendering components on 3ds Max (standard lights, procedural textures etc) may produce different results between AMD/Intel machines.

Best regards,
Vlado

[Morbid Angel]

vlado any reason why AMD and Intel produce different results?

[KAKTUSDIGITAL]

Thankyou Vlado, and thats wonderful to hear

[natty]

Hi
We have a mix of 32bit and 64bit AMD and Intel machines, the results have always been the same ...

[dlparisi]

They haven't always been the same...http://www.chaosgroup.com/forums/vbu...ad.php?t=40143 I never verified any problems with DR buckets though. SP2 seems fine though with DR and BB.

[natty]

See what you mean .. although we have never run into this problem on our farm.

[vlado]

vlado any reason why AMD and Intel produce different results?

Some calculations (e.g. sin, cos, square root, etc) may be slightly different in the minor digits after the decimal point (e.g. where one processor gives a result of 2.7612543 the other might give 2.7612542). For most cases this is alright, but if such errors accumulate over a long chain of calculations, the end result may end up being significantly different.

Best regards,
Vlado