AMD announces GPUOpen - Open Sourced Gaming Development

[GoogalyMoogaly]

Really?

Are we reading the same forums? Surely with Nvidia's 80/20 dominance that cannot be even remotely true.

These forums are so Nvidia biased it is beyond belief. Hence why the few AMD users need to be more vocal.

Just completely surprised how you came to that conclusion.

Nvidia's 80/20 dominance does mean much in a place like this though. I think you'd also get more AMD users than Nvidia on the AMD forums too.

It's just a feeling I get from reading the forums, combined with that poll AMDMatt did a while back.
To me it seems like Nvidia users are in the minority and that's why there are a few 'loud' ones.

For me it's hard to believe that anyone doesn't feel this is an AMD forum. The number of anti-Nvidia threads compared to the amount of anti-AMD threads contributes to this. There's almost always another thread about GameWorks being bad or AMD tech being good. Which seems unlikely if this was an Nvidia dominated forum.
To me when someone says this is an Nvidia forum it just feels like AMD trying to put themselves in the position of victim again.

 

[Insanties_birth]

Again, if the implementation of the effect is closed source anything could have been changed. They could bare almost no resemblance to the TressFX code in GitHub. I don't see how this would be any easier to to spot dodgy tactics with than GameWorks.

I'm not suggesting that it is likely to happen and if it were it'd probably be more likely that Nvidia provide an 'enhanced' version than AMD (due to the fact it'd take effort and AMD are allergic to that).
I'm just saying that because the initial source code is open it doesn't mean that what is implemented in the game will be or that devs will use the source code unchanged.
Then if a developer did have a modified version it seems reasonable that the developer would keep a private version of the code with their changes in that they could use in all their games.

So what we might end up with is instead of GameWorks gimping performance we could have GameWorks and 17 private forks of GPUOpen all gimping performance for one side or another. Finding these things out and doing any sort of driver optimising will be even harder.

It can be but the idea that they would opt for an open source software to then deliberately choose to make a closed source and damaging coding in the end is unlikely. Like with Crysis 2 sometimes people gain more access to some evidence as to what is causing the issues so since the code for this is open it'd be easier to compare what has been changed if they did this or even just blindly tested performance in different areas. If AMD is only handing out the open source stuff and not the closed stuff then it's still going to be better off initially as at least some of it has had scrutiny (unlike gameworks), it would require bigger changes to get this then to be damaging to the opposition (making it less likely due to wasted time and resources) and any change to that isn't really what gpuopen is about. If a developer chose to damage performance for Nvidia that would be completely separate to this open source code anyway, it's not necessarily designed to stop any and all potential misuse BUT it does have more scrutiny initially and by leaving it open source it not only allows optimisation and growth for both ends but it doesn't have forced influence from AMD. Partners can take the code and do what they want with it but with gameworks they very much have to work around the way Nvidia want it done.

Quite simple really but the whole idea of open source is they take it and do what they want with it, incorrectly arguing that AMD could become evil and choose to influence it afterwards doesn't change that the project itself has nothing wrong about it. That's like saying if we give charity directly through the government rather than directly through the charity it's IMPOSSIBLE to know that they won't be corrupt too so it's shady. Yes, we can't 100% rule out a dev could by there own measures choose to change what is designed to be a good thing but that has nothing to do with the open project and the way it's being delivered. As I said, conjecture that it can be corrupted is possible for nearly everything in life but it doesn't change that a more open structure is still better and the fact they likely give this stuff for free and leave it open so devs can readily access the none biased code means any change would be of the developers choice more than likely and that is not something we can likely assume to occur. As you can probably and logically deduce, if there were 17 forks of gpuopen it'd probably not be AMD creating each of those so it is down to the dev to keep it pure but AMD themselves wouldn't be the ones causing the issue in that case. If the argument is simply that AMD could sponsor them and choose to corrupt it then sure, that can be bad but it's the case with anything, the sponsoring would be distinctly separate to the fact this stuff is open and available (as far as I'm aware) to anyone without fee though so wouldn't require they have any need to corrupt the software.

 

[Bazzards]

As I read more and more Nvidia conspiracies I just move more and more towards them.

The way AMD are running the company they deserve to go down and the fans desperate attempt's at putting a black mark against Nvidia becomes laughable, only AMD can save themselves, but they seem to be on self destruct. Their new cards will have to be particularly good for me move, as I actually enjoy the Gameworks and efforts that they put in with developers.

 

[meldarthx]

It means nought if nobody knows if they are doing anything though.

FFS has no one bothered to actually think; Nvidia paid through the noise on tomb raider and put it in the contracts AMD actually can't same much about pure hair......that's only reason I can possibly think why AMD hasn't said anything about pure hair.......because they can't

 

[Mauller]

Nvidia's 80/20 dominance does mean much in a place like this though. I think you'd also get more AMD users than Nvidia on the AMD forums too.

The market share is not 80/20... That was sales over a period. that does not equate to market share as many of those sales can be the result of people upgrading older hardware with replacement hardware from the same manufacturer.

The steam survey is more accurate for actual market share. yes amd is around 24% but nvidia is at 54% not 80% of the market. and that difference becomes 2/3 rds for nvidia and 1/3 for amd if you just consider nvidia and amd.

 

[GoogalyMoogaly]

Fair enough, but personally reading your posts as an altruistic approach that looks more like ripping anything AMD to bits, considering the mass migration to Nvidia, maybe you'll swing the other way, who knows, as I said before, would love to see the big Nvidia hitters getting asked some of your questions and see them squirm like the AMD ones do.

I might not be the best communicator but I'm sure yo know where I'm coming from.



IMO no, as a dev can't control anyone else's IQ hit, they can only control their own audiences destiny, plus in this instance, (as it's clear as day)it's non agnostic, there is a minimal hit that is nowhere near GW's sometimes sledgehammer performance impact regardless the vendor.

Who knows out with this one GPUO instance what is going to happen, it remains to be seen what transpires.

To me I'm just playing devil's advocate in some of the AMD hyping or Nvidia bashing threads. Since you side with AMD I can understand why it might seem that way to you though.

I don't see a migration to Nvidia (if it happens, which I can't see) changing this. People will still be biased the way they are regardless of the tech they use. I know you have a Nvidia card and GSync, but I think most still see you as an AMD man. I own at least double the AMD GPU than Nvidia GPUs, including 2 Fury X cards and I own a Freesync monitor, but people still say I'm an Nvidia man. So the hardware you own doesn't make a difference.

As I said, performance penalties is quite a different argument to the open-source = good, closed-source = bad that goes on in Nvidia discussions. At least as far as visibility goes. Yes the developer has control and so could balance/optimise for both sets of hardware, but people (including a recent video that caused a lot of 'discussion') blamed Crysis 2's over tessellation on Nvidia. If Nvidia can be blamed for how Crytek wrote the code for their game because of a sponsorship or something, why couldn't the same apply to something like PureHair? Say Oxide use it in their next game, which I would guess has a fairly good chance (in the 600-600% region) of being AMD sponsored, and AMD ask them to make Nvidia cards use a different code path or just make it use unnecessary amounts of Async Compute. Maybe AMD even provide them with a pre-customised version they can optimise, for AMD cards. If Oxide never have to release the source code for the version they use, what's stopping them just because there's a vanilla version in GitHub?

Also, all the talk of AMD needing to identify PureHair as being developed on top of TressFX for brand recognition may be over-estimating the general awareness of TressFX (outside of these sorts of communities). I also doubt GameWorks is that widely known either, a lot of people just want to game and don't concern themselves with the physics engine in use, etc.

The market share is not 80/20... That was sales over a period. that does not equate to market share as many of those sales can be the result of people upgrading older hardware with replacement hardware from the same manufacturer.

The steam survey is more accurate for actual market share. yes amd is around 24% but nvidia is at 54% not 80% of the market. and that difference becomes 2/3 rds for nvidia and 1/3 for amd if you just consider nvidia and amd.

Don't tell me, tell the person I quoted, they used the figures first!
Why have a go at me about it and not them?

Also, doesn't the steam survey include Intel and AMD iGPUs where as the 80/20 is referring to discrete GPUs?

 

[elmuzzy66.]

FFS has no one bothered to actually think; Nvidia paid through the noise on tomb raider and put it in the contracts AMD actually can't same much about pure hair......that's only reason I can possibly think why AMD hasn't said anything about pure hair.......because they can't

Are we going to be asking for contracts to be shown again?

 

[Mauller]

Don't tell me, tell the person I quoted, they used the figures first!
Why have a go at me about it and not them?

Also, doesn't the steam survey include Intel and AMD iGPUs where as the 80/20 is referring to discrete GPUs?

Apologies, i missed you quoting that from maonayze, was not meant to seem like i was having a go.

Yeah it does show iGPU's as well, but it better represents the market share as it shows what people are using.

The funny thing about the sales figures is that even with 80/20 people buying, those 80% could all be nvidia users to begin with who are refreshing systems.

Like with all statistics, people can make it show what they want by fiddling the data. Not that the company did that. But unless we saw the original data which i can't seem to find such as sales numbers, then making a valid conclusion is harder.

 

[Insanties_birth]

As I read more and more Nvidia conspiracies I just move more and more towards them.

The way AMD are running the company they deserve to go down and the fans desperate attempt's at putting a black mark against Nvidia becomes laughable, only AMD can save themselves, but they seem to be on self destruct. Their new cards will have to be particularly good for me move, as I actually enjoy the Gameworks and efforts that they put in with developers.

No ones being desperate, no ones even trying to blame Nvidia in this thread but it's just a simple comparison that open source is better than closed. We've seen closed source cause poor performance in near all gameworks titles and open source is simply better in that regard as it's easier for both sides to openly work towards optimisations.

It doesn't matter what kind of childish confirmation biases you use with broken logic but this is no different to people trying to argue against corruption (just an example, don't cry and take it literally) such as saying another method of action could stop more potential abuse. Why would improvements be excuses? What infantile logic. You're even trying to use the excuse that you dislike that AMD fans (who in this regard are speaking there own minds rather than AMD's) to justify that you dislike AMD? Gameworks is good when you're using it, no one would deny such a thing as it's simply adding additional effects but the way Nvidia do it has led to nearly every gameworks game being a mess at launch and this is just another example. The amount of broken logic you've displayed in a few short sentences has already made me feel the worry of trying to convince you of anything but it's rather obvious that Nvidia put effort in at the expense of the entire PC gaming community. It benefits them and there users but if they wasn't poor at keeping performance up for others there wouldn't be anyone arguing against it. Either way I don't think I'll start another gameworks argument as it's good stuff but it's just so poorly utilised it's practically designed to hamper performance for others, anyone can see it but the blind. It seems that if you really have read that many Nvidia conspiracies then surely there's enough examples of potential misdoings is there not? Oh wait, if anyone has a different opinion than you then that is an excuse for you to blame AMD and buy Nvidia cards so I best be quiet to prevent your broken logic influencing you further.

 

[CAT-THE-FIFTH]

Also, all the talk of AMD needing to identify PureHair as being developed on top of TressFX for brand recognition may be over-estimating the general awareness of TressFX (outside of these sorts of communities). I also doubt GameWorks is that widely known either, a lot of people just want to game and don't concern themselves with the physics engine in use, etc.

I know plenty of computer gamers who know about things like PhysX and "Gameworks" and think its a value added feature,and that Nvidia is "better" for gaming. You got to realise Nvidia are not alone in doing this -companies like Apple mastered this kind of advertising and it paid dividents,and even companies like Samsung are now doing the same.

It also extends to things like cameras,with Nikon and Canon doing pretty much the same and looking down on brands like Pentax and Olympus who are just as old and produce decent equipment.

Remember,this is the era of "info-bytes". People will not generally do much research in depth about things,and whoever can get their message out there the most wins by default.

Enthusiasts like us are interested in trying to read up on stuff and make up our own minds on things,but we are a minority.

If AMD does not try and sell itself,and what is does,it won't be 70% to 80% of people wanting a new GPU who buy Nvidia but more.

Nvidia as a company has understood marketing very well,even down to things like the Nvidia Focus Group,a decade ago,and even when they had the disaster which was the Nvidia FX which had crap hardware and even had issues with major releases like HL2,still outsold the Radeon 9500 and 9700 series.

The thing is ATI seems to have been better at marketing still when compared to AMD. The X800 series lacked SM3.0 DX9 support and it still managed for the only time in its history to actually surpass Nvidia in sales,so they at least capitolised on the eventual ill will from the FX series. That was despite the Nvidia 6000 series being probably better cards overall.

Even during the dark days of the disaster which was the HD2000 series,and the fact that top card of the follow up HD3000 series,ie,the HD3870 GDDR4 could not even beat the third tier card on the Nvidia side,the 8800GT,ATI never had what was happening now,ie, Nvidia outselling them 4 to 1.

That was with a product stack which petered out at around £150 in desktop for a single GPU card.

There is something not going right with AMD the last few years. It makes me concerned whether the will **** up the Polaris launch by doing something stupid.

After all the R9 290,R9 285 and Fury X launches were somewhat of a disaster for AMD,which could have been salvaged by them if they paid more attention to the details.

The R9 295X2 was probably the only launch in the last two years or so which went well and to some degree the rebrand launches were OKish. Everything for Nvidia since the GTX750TI has been fantastic bar the Titan Z which Nvidia PR made sure was not sampled for reviews.

 

[CAT-THE-FIFTH]

FFS has no one bothered to actually think; Nvidia paid through the noise on tomb raider and put it in the contracts AMD actually can't same much about pure hair......that's only reason I can possibly think why AMD hasn't said anything about pure hair.......because they can't

No,because just because they paid the dev to say nothing means they can't stop AMD talking about their own tech.

A simple PR puff piece - "As part of our commitment to vendor neutral,GPU effects,we allowed Crystal Dynamics,who we worked with on Tombraider on the TressFX hair technology, to use TressFX3.0 source code as a base for their new Purehair technology,which is not only cross platform,but shows massive performance improvements accross platforms,enabling fluid animation of Lara's hair on the XBox version....and so on....and shows our continued comitment to vendor neutral effects which benefit all gamers whether console or PC" or something more PR statement like.

That's all they needed to say at release or even a day beforehand. Just an information byte,to indicate they had some involvement. It get's picked up by a few news sites and that's it.

Plus also FFS they need to update their TressFX page. Its been frozen in time since Tombraider it appears.

 

[tommybhoy]

^
Wasn't very hard was it?

To me I'm just playing devil's advocate in some of the AMD hyping or Nvidia bashing threads. Since you side with AMD I can understand why it might seem that way to you though.

I don't see a migration to Nvidia (if it happens, which I can't see) changing this. People will still be biased the way they are regardless of the tech they use. I know you have a Nvidia card and GSync, but I think most still see you as an AMD man. I own at least double the AMD GPU than Nvidia GPUs, including 2 Fury X cards and I own a Freesync monitor, but people still say I'm an Nvidia man. So the hardware you own doesn't make a difference.

As I said, performance penalties is quite a different argument to the open-source = good, closed-source = bad that goes on in Nvidia discussions. At least as far as visibility goes. Yes the developer has control and so could balance/optimise for both sets of hardware, but people (including a recent video that caused a lot of 'discussion') blamed Crysis 2's over tessellation on Nvidia. If Nvidia can be blamed for how Crytek wrote the code for their game because of a sponsorship or something, why couldn't the same apply to something like PureHair? Say Oxide use it in their next game, which I would guess has a fairly good chance (in the 600-600% region) of being AMD sponsored, and AMD ask them to make Nvidia cards use a different code path or just make it use unnecessary amounts of Async Compute. Maybe AMD even provide them with a pre-customised version they can optimise, for AMD cards. If Oxide never have to release the source code for the version they use, what's stopping them just because there's a vanilla version in GitHub?

Also, all the talk of AMD needing to identify PureHair as being developed on top of TressFX for brand recognition may be over-estimating the general awareness of TressFX (outside of these sorts of communities). I also doubt GameWorks is that widely known either, a lot of people just want to game and don't concern themselves with the physics engine in use, etc.

I'm under no illusions AMD wouldn't try the same if they were in the same position as Nvidia.

Yes, your hypothetical questions could hold basis but I have only been talking based on what we have to go on now from a gamers pov, but if an unfair advantage was to be found then it would be as damaging as GW's if Nvidia couldn't fine tune driver performance in the same way as GW's does for AMD/Nv.


Which I have stressed concern from the very beginning with GW's that any vendors stranglehold isn't in the best interest, until if it changes, Nv is what I'll be running from here on in if AMD can't compete with a comparable amount of AAA titles as I buy most of them bar rts.

 

[GoogalyMoogaly]

^
Wasn't very hard was it?



I'm under no illusions AMD wouldn't try the same if they were in the same position as Nvidia.

Yes, your hypothetical questions could hold basis but I have only been talking based on what we have to go on now from a gamers pov, but if an unfair advantage was to be found then it would be as damaging as GW's if Nvidia couldn't fine tune driver performance in the same way as GW's does for AMD/Nv.


Which I have stressed concern from the very beginning with GW's that any vendors stranglehold isn't in the best interest, until if it changes, Nv is what I'll be running from here on in if AMD can't compete with a comparable amount of AAA titles as I buy most of them bar rts.

I'm not saying there's anything wrong with TressFX 3.0 or PureHair, but if companies are allowed to make changes and keep source code private it's theoretically possible that implementations that are vendor biased and closed source could occur. In fact nobody may actually use the vanilla code.
My point is that there's no guarantee that GPUOpen will be unbiased and open-source in every game. People seem to be suggesting this is the answer to all problems, in my devils advocate role I'm just saying the way it's actually used could be as bad as GameWorks.

We have one example used so far, so there's a lot of speculation, nobody really knows how it's going to be used. If people are right that the reason devs have used GameWorks up to this point is because Nvidia payed them too, then I see no reason for that to change as I doubt Nvidia are going to go "GPUOpen is out, best stop paying off the developers and let them make their own choice now there's a rival package of effects out".

Off topic, but I'll say now that while we often don't agree or argue for the same side, I actually quite like you (Tommy) and a number of the other's that I might disagree with regularly. I'm less keen on some of those that stop arguing about the matter at hand and just start insulting me on a personal level though... (I'm sure both sides do this, but I try never to make one of these arguments personal)

 

[AlamoX]

I'm not saying there's anything wrong with TressFX 3.0 or PureHair, but if companies are allowed to make changes and keep source code private it's theoretically possible that implementations that are vendor biased and closed source could occur. In fact nobody may actually use the vanilla code.
My point is that there's no guarantee that GPUOpen will be unbiased and open-source in every game. People seem to be suggesting this is the answer to all problems, in my devils advocate role I'm just saying the way it's actually used could be as bad as GameWorks.

We have one example used so far, so there's a lot of speculation, nobody really knows how it's going to be used. If people are right that the reason devs have used GameWorks up to this point is because Nvidia payed them too, then I see no reason for that to change as I doubt Nvidia are going to go "GPUOpen is out, best stop paying off the developers and let them make their own choice now there's a rival package of effects out".

Off topic, but I'll say now that while we often don't agree or argue for the same side, I actually quite like you (Tommy) and a number of the other's that I might disagree with regularly. I'm less keen on some of those that stop arguing about the matter at hand and just start insulting me on a personal level though... (I'm sure both sides do this, but I try never to make one of these arguments personal)

you are assuming that devs will be unbiased when making effects and favoring AMD, i will grant you that, it is possible for both opengpu and gameworks, the difference between the 2 thou is this, if that happens AMD doesn't have access to the code to optimise it, while Nvidia have full access to the source code, and even as you say if the code is heavily modified by Devs, it's just impossible for a studio to keep it closed to a hardware vendor like Nvidia or Intel, the same as any other effect the studio develops.
so you can't really claim that AMD does with GPUOpen exactly what Nvidia does with Gameworks, or that we are back to the same problem we had with GW, because AMD never blamed nvidia for using gameworks on games, they blamed them for closing the code to them, and prevent proper optimisation incase (foul play) occurs.

 

[tommybhoy]

I'm not saying there's anything wrong with TressFX 3.0 or PureHair, but if companies are allowed to make changes and keep source code private it's theoretically possible that implementations that are vendor biased and closed source could occur. In fact nobody may actually use the vanilla code.
My point is that there's no guarantee that GPUOpen will be unbiased and open-source in every game. People seem to be suggesting this is the answer to all problems, in my devils advocate role I'm just saying the way it's actually used could be as bad as GameWorks.

We have one example used so far, so there's a lot of speculation, nobody really knows how it's going to be used. If people are right that the reason devs have used GameWorks up to this point is because Nvidia payed them too, then I see no reason for that to change as I doubt Nvidia are going to go "GPUOpen is out, best stop paying off the developers and let them make their own choice now there's a rival package of effects out".

Can't argue with any of that, never thought we'd see the day.

Off topic, but I'll say now that while we often don't agree or argue for the same side, I actually quite like you (Tommy) and a number of the other's that I might disagree with regularly. I'm less keen on some of those that stop arguing about the matter at hand and just start insulting me on a personal level though... (I'm sure both sides do this, but I try never to make one of these arguments personal)

Well I was wrong, we manged a convo, you are not to bad yourself too(sometimes), I'll just need to bite my tongue.

At the rate things are going and the attention coming my way, I'll be agreeing with you more often anyway.

 

[CAT-THE-FIFTH]

It just shows you how half arsed AMD is at promoting themselves. All they need to say is if TressFX is used as the basis of any hair effects,for AMD to be named as part of the deal for AMD R and D into TressFX being appropriated by other companies.

A simple case of Purehair powered by AMD TressFX technology or AMD Open Physics technology.

There is a reason why TressFX based technology was used in Tombraider - it was running on AMD GPUs in the XBox One and we can see it is efficient enough to be able to run on one. So,AMD should have grown some balls and said if that tech is used in the PC version for AMD to be acknowledged.

Instead,AMD just rolled over and got trolled by Nvidia. The sad thing is I doubt they are even aware that Nvidia just trolled them on their website.

 

[D.P.]

Nvidia's 80/20 dominance does mean much in a place like this though. I think you'd also get more AMD users than Nvidia on the AMD forums too.

It's just a feeling I get from reading the forums, combined with that poll AMDMatt did a while back.
To me it seems like Nvidia users are in the minority and that's why there are a few 'loud' ones.

For me it's hard to believe that anyone doesn't feel this is an AMD forum. The number of anti-Nvidia threads compared to the amount of anti-AMD threads contributes to this. There's almost always another thread about GameWorks being bad or AMD tech being good. Which seems unlikely if this was an Nvidia dominated forum.
To me when someone says this is an Nvidia forum it just feels like AMD trying to put themselves in the position of victim again.

This is definitely an AMD forum. It may well be that more OCUK members own nvidia cards but they certainly don't make themselves known around here in anywhere near the numbers of the AMD fans. It's always been this way.

 

[D.P.]

It just shows you how half arsed AMD is at promoting themselves. All they need to say is if TressFX is used as the basis of any hair effects,for AMD to be named as part of the deal for AMD R and D into TressFX being appropriated by other companies.

A simple case of Purehair powered by AMD TressFX technology or AMD Open Physics technology.

There is a reason why TressFX based technology was used in Tombraider - it was running on AMD GPUs in the XBox One and we can see it is efficient enough to be able to run on one. So,AMD should have grown some balls and said if that tech is used in the PC version for AMD to be acknowledged.

Instead,AMD just rolled over and got trolled by Nvidia. The sad thing is I doubt they are even aware that Nvidia just trolled them on their website.

That would make sense but that isn't how open source software works, if AMD put it out there license free then this is what they get. If AMD want to require developers to name AMD when they use GPUOpen then it is licensed softwre just like Gameworks, which you can get the source for as well.

 

[AlamoX]

This is definitely an AMD forum. It may well be that more OCUK members own nvidia cards but they certainly don't make themselves known around here in anywhere near the numbers of the AMD fans. It's always been this way.

we are all Nvidia fans pretending to be AMD fans, the trolling is real, beside they are going to close up shop soon, why not give them glimmer of hope on the forum.

 

[GoogalyMoogaly]

you are assuming that devs will be unbiased when making effects and favoring AMD, i will grant you that, it is possible for both opengpu and gameworks, the difference between the 2 thou is this, if that happens AMD doesn't have access to the code to optimise it, while Nvidia have full access to the source code, and even as you say if the code is heavily modified by Devs, it's just impossible for a studio to keep it closed to a hardware vendor like Nvidia or Intel, the same as any other effect the studio develops.
so you can't really claim that AMD does with GPUOpen exactly what Nvidia does with Gameworks, or that we are back to the same problem we had with GW, because AMD never blamed nvidia for using gameworks on games, they blamed them for closing the code to them, and prevent proper optimisation incase (foul play) occurs.

I'm not saying AMD would do it, or at least not directly, it could be done through contracts or something.
But the code could be closed to Nvidia to prevent optimising if it is modified and the code isn't made available to Nvidia. You say that a studio couldn't keep it closed to a vendor, but that's exactly what people say happened with GameWorks. I believe devs could get access to that source code (maybe for a fee) but in the contract they signed to get it I believe it was stipulated they couldn't share it with AMD. Why couldn't AMD implement such a contract to prevent Nvidia access the altered TressFX source code?

Again, this is all a big hypothetical and in the past there doesn't seem to have been any evidence that AMD have done this sort of thing, except for rumours that it was part of the contract with AMD that Lichdom wouldn't allow Nvidia users to enable TressFX.
The point is that the only source code everyone has access to is the vanilla source code in GitHub. Any modifications may not be made visible to the community, like GameWorks. In this scenario the modified versions of TressFX that are actually used could have any number of changes in it, some which may favour one side over the other, on purpose.
No reason Nvidia couldn't come up with a contract allowing the use of GPUOpen effects in their TWIMTBP titles on the condition that the modified source code isn't made available to AMD. Nvidia could then send people in to help make changes that work better on Nvidia hardware in some way or unless certain driver optimisation are implemented specifically for that game.
TL;DR - Vanilla TressFX being open-source doesn't mean any modified version will be and thus the issues people have with GameWorks could also occur in the modified TressFX code. In theory.

*** Unless part of the licence agreement to use GPUOpen in the first place states that any modified versions must be available under the same licence. ***