HOW MUCH SHOULD THIS MAT­TER TO YOU?

HWM (Malaysia) - - LEARN -

But if all DirectX 12 cards will get to en­joy the ad­van­tages of the un­der­ly­ing API, does that mean that fea­ture level sup­port is in­con­se­quen­tial? That de­pends.

The Fiji GPU on AMD's flag­ship Radeon R9 Fury X uses the lat­est Graph­ics Core Next (GCN) 1.2 ar­chi­tec­ture and sup­ports DirectX fea­ture level 12_0. On the other hand, top NVIDIA cards us­ing the GM200 GPU like the GeForce GTX TI­TAN X and 980 Ti sup­port fea­ture level 12_1.

One edge that NVIDIA has is sup­port for con­ser­va­tive ras­ter­i­za­tion with fea­ture level 12_1. Shad­ows are one of the more dif­fi­cult things to ren­der in a true-to-life man­ner, but con­ser­va­tive ras­ter­i­za­tion en­ables smoother and more nat­u­ral shad­ows, which is some­thing that will be read­ily ob­served by end users.

On the other hand, AMD's GCN 1.2 ar­chi­tec­ture sup­ports Re­source Bind­ing Tier 3, which – thanks to some back­end changes that don't re­quire the CPU to work as hard – im­proves per­for­mance and makes for a more ef­fi­cient graph­ics pipe­line. How­ever, un­like con­ser­va­tive ras­ter­i­za­tion, th­ese changes don't trans­late into any on-screen eye candy, so NVIDIA may in fact have the ad­van­tage here, at least in terms of per­ceiv­able ben­e­fits.

But let's re­turn to the ex­am­ple of the Radeon R7 370. The card only sup­ports fea­ture level 11_1, whereas the NVIDIA GeForce GTX 950 sup­ports fea­ture level 12_1. In the world of prod­uct mar­ket­ing – where facts are of­ten blurred – this has led to claims that AMD cards, in­clud­ing GCN 1.2 cards such as the Radeon R9 Fury X, don't fully sup­port DirectX 12.

This is slightly mis­lead­ing, be­cause no sin­gle graph­ics card sup­ports the en­tire set of DirectX fea­tures. For in­stance, the NVIDIA GeForce GTX TI­TAN X and 980 Ti only sup­port Re­source Bind­ing Tier 2 (com­pared to Tier 3 on AMD's GCN 1.2 cards), de­spite their much-vaunted fea­ture level 12_1 sup­port.

At the end of the day, there's just one key take­away: full sup­port for DirectX 12 is a myth. Each card from NVIDIA and AMD both sup­port dif­fer­ent fea­ture sets, and it's up to you to de­cide which mat­ter more, or if at all.

NOVEM­BER 2015

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HWM

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Re­gard­less of whether they sup­port fea­ture level 12_0 or 12_1, no one card sup­ports the en­tire set of DirectX 12 fea­tures.

Fig­ure 8: Reg­u­lar Shadow Map

Con­ser­va­tive ras­ter­i­za­tion al­lows for more nat­u­ral shad­ows.

Fig­ure 9: Ray Traced - Con­ser­va­tive

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