At one point in time Alias used to run only on SGI workstation and IRIX OS. Slowly over time it was ported to many different hardware/OS, like IBM/AIX, HP/HPUX, SUN/Solaris. During that time the hardware was expensive and limited. But neverthless, the stability of Alias on IRIX was remarkable. Finally with V10 it was ported to PC and recently to Mac.
Some of the OpenGL/Hardware features which were required for Alias.
- Unified back/depth buffer: This is a technique (relevant when high speed memory was expensive) in which multiple windows shared the same desktop size back/depth buffer. Cards which do not have this feature in hardware ( gaming cards ) will need to allocate separate memory for each of the modeling windows... With multiple windows open, the memory will soon run out and additional software techniques need to be employed which will slow down the performance.But in recent times with low memory prices and introduction desktop eye candy like Windows Aero and OSX desktop effects, which requires compositing ( translucency, shadows other effects of windows ), this feature has almost become irrelevent. In fact new versions of Alias requires this feature to be turned off for proper functioning.
- Overlay planes: Some of the visual items such as menus, marking menus etc. obscure the window beneath it. Hardware overlay planes are additional memory space used to draw those items directly, without having to swap memory between the visual layer. As of v13 the overlay plane requirement for Alias has been discontinued. In some instance, there is a performance improvement if the overlay planes are disabled.
With the recent advances in general programability in garphics hardware and techniques in OpenGL 2, Alias performance on recent Geforce cards are satisfactory. Quadro based cards have additional hardware accelerated features, such as Anti-aliased lines and clip regions etc., which can improve the interactive performance of Alias especially if Hardware Anti-aliasing is turned on. Where as Geforce cards will shows horrendous artifacts if hardware anti-aliasing is turned on in Alias. In any case the sofware anti-aliasing in Alias works really good for most occasions. I have heard that ATI Radeon cards show many artifacts but do not have much experience on Radeon cards.
If you look at some of the qulified hardware for Alias on Mac, one would see cards like Geforce 9600M and Gt120, which are, accordingy to nVidia, "consumer" cards. I wonder how consumer cards get qualified for Mac while similar cards are not qualified for PC!
Alias 2013 and above hardware anti-aliasing using Nvidia Geforce gives decent performance without any artifacts.
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