We don't. You guessing is not us knowing.
Andrew Lauritzens posts have confirmed my former speculations and critique, besides Karis comments on twitter.
It's true: RT APIs can't do LOD.
But if your agenda dictates, prefer to classify truth as speculation, just because you don't like it to be true.
Epic choose what they implement for what feature/performance level.
Their users decide which path to use.
Neither of us blames them to give both options.
But both of us should blame the failure on API design, so we can get that RT future you desire so badly, and i need as well.
Do we? UE5 needs it because it targets mobile platforms
I did not mean mobiles. I mean PC platform. Last time i checked RT support on Steam HW survey it was less than 20%. Idk what's the percentage now, but i would support old non RT HW during the entire console generation, at least.
Currently RT is the option, not the standard. Due to bad economy, Moores Law stagnation, and success of low power portable gaming, i'm no longer sure we'll ever have 'powerful enough' HW RT an all platforms.
I believed in this when RTX was announced much more than i do now.
Regardless of my opinion, SW alternatives to lighting, if they are faster and better, do not hold back progress of RT, nor do they turn RT redundant.
RT is not the best tool for every problem, but it's nice to have it. There is not really a disagreement about that. But still we manage to divide us into two camps, forcing both sides into narrow and extreme corners, turning arguments weak and attackable, making both of us look silly.
we also know that this is an engine world design issue, not a h/w RT issue.
Yes, but it's all about games. World design, artist workflow, compression requirements are more important than photorealism.
And it's not a HW issue - it is a API issue, so actually SW. That's my whole point of why i think we should not argue even if details about our visions differ.
It can be fixed, so we should focus on agreement on the fix, instead focusing on disagreement on which path will bring us to the common goal.
Why am i almost the only one here proposing such fix? Why do so many defend a broken status quo?
Neither can s/w RT in UE5 as it's using SDF simplification for that.
Yes, but my point is: A software implementation of RT could support Nanite. Because there would be no API blackboxes preventing a 'lodable' BVH.
And h/w RT likely can support Nanite but it should be implemented differently for that.
HW can support Nanite. It's just triangles in a tree, so yes. There is no need to change the HW.
All we need is to open up BVH. So we can modify the data structures as needed to implement LOD changes.
That's the only way forwards.
The alternative is custom formats to implement something like Nanite in HW directly, using custom, blackboxed, probably even proprietary data structures.
But that's the bad way. Forwards for some time at limited focus, but again backwards on the long run. Because:
Nanite and LOD is just an example to illustrate balckboxed BVH is not acceptable. We need control over dynamic geometry in general, and BVH is too useful to restrict it to RT only.
Now in a time where HW progress is stagnating, we need flexibility more than ever. Because felxibility enables SW progress, and SW progress becomes now more important and faster than HW progress.
Notice this is not my guessing or predictions - it is the only conclusion besides having no more progress at all, which i'm not willing to accept.
You say that even more fixed function is the proper reaction to the stagnation, but time already proved you wrong. Because of that raster -> T&L -> VS+PS -> general compute progression, which became the winner. So the trend is away from fixed function, not towards it.
The real and only problem here is that RT, as an entirely new and complex feature, does not evolve fast enough towards more flexibility.
And the irony is that it's not related to fixed function HW, but only comes from API design failure, politics and bureaucracy issues.
So again, our differing opinions do not really matter and are pointless to discuss.
However, personally i can not get out of my 'contra RT corner' as long as you guys do not accept the fact that there is a problem.