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ALS and Rembrandt

Graphics issues like: bad framerates, weird colors, OpenGL errors etc. Bad graphics ar usually the result of bad graphics cards or drivers.
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ALS and Rembrandt

Postby zbot473 » Tue Nov 21, 2017 2:25 am

Why is it not possible to have Rembrandt and ALS on at the same time? I really like both... :cry:
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Re: ALS and Rembrandt

Postby bugman » Tue Nov 21, 2017 9:31 am

Try speaking English and Spanish at the same time - i.e. simultaneously - and you'll encounter similar problems ;) This is the difference between deferred shading used in Rembrandt and standard OpenGL shading used in ALS (and the default renderer). Some aspects of ALS could probably be ported to Rembrandt. However note that Rembrandt is essentially now dead, as the sole developer of this framework has permanently left the project. Hence Rembrandt as a project will, currently, not move forwards.

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Re: ALS and Rembrandt

Postby FighterAce » Thu Nov 30, 2017 12:36 am

Is Rembrandt really dead? That's sad, I would love to see further development with it.
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Re: ALS and Rembrandt

Postby Thorsten » Thu Nov 30, 2017 7:30 am

Is Rembrandt really dead?


I guess that depends on your definition of dead. There's no plan I'm aware of to remove it, but there's no maintainer either - by and large we try to make sure it doesn't get accidentially broken, but that's about it.

That's sad, I would love to see further development with it.


Feel free to step in - since it's unmaintained, you're free to develop it into any direction you fancy.
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Re: ALS and Rembrandt

Postby Hooray » Sun Dec 03, 2017 11:29 am

zbot473 wrote in Tue Nov 21, 2017 2:25 am:Why is it not possible to have Rembrandt and ALS on at the same time? I really like both... :cry:


Technically, the two frameworks have different methods to create the final frame (image).
They have a handful of "ingredients" at their disposal and they can combine these in different ways - but sooner or later, the two methods are starting to diverge too much, so that they are no longer compatible, but even mutually-incompatible (conflicting).

If all that sounds too techncial to make sense, consider the following:

Image

Obviously, at some point you need to decide how you'd like your eggs - and no matter what, "going back" to revert the decision is no longer an option.

Obviously, that's an over-simplification - but it's really not that far-fetched, because what is really happening behind the scenes is much more complex than the difference between scrambled or fried eggs, so that "reverting the recipe" really is not an option - which isn't to say that you cannot add ketchup (read: have night vision) to either, but the process will be hugely different.
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Re: ALS and Rembrandt

Postby iamzac » Mon Dec 04, 2017 7:03 pm

Are there more details somewhere about this issue?
Because I see that I can run two flightgear instances at the same time on my not so great nvidia 950 so why isn't then possible to run for example an instance of rembrand and an instance with ALS in paralel and then put the rembrand plane inside the ALS scenery?
There would be a performance hit but if an average (or bellow average from a gamers point of view) PC like mine can run two flightgears at the same time this would be even more efficient because lots of other things would remain shared.
Now I have no experience in 3D programming, I am just a general programmer, so what I said could be very stupid but I am curious.

EDIT: I took a screenshot of a test i did with both running at the same time:

Image

Before starting the second instance the ALS one had 45 fps, it seems that running two ALS versions in parallel kind of works but ALS and rembrandt makes the rembrandt unusable (although I do have everything at maximum in rembrandt).
As you can see from the temperatures and the system load that I let in the screenshot in the taskbar the system is not overloaded by this crude example.
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Re: ALS and Rembrandt

Postby bugman » Mon Dec 04, 2017 8:19 pm

iamzac wrote in Mon Dec 04, 2017 7:03 pm:... I am just a general programmer ...


Then maybe this analogy might help - try programming an algorithm using both a for loop and recursion simultaneously ;) The concepts/designs are simply incompatible.

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Re: ALS and Rembrandt

Postby curt » Mon Dec 04, 2017 8:34 pm

I think the biggest factor is that Frederic, the architect of Rembrandt left the project several years ago. The subject matter is difficult enough that no one else has jumped in with the necessary background & understanding and the time & energy to figure it all out and continue the development trajectory. I'm sure many ALS features could be merged into the Rembrandt system, but it's really tricky difficult stuff.
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Re: ALS and Rembrandt

Postby Thorsten » Tue Dec 05, 2017 6:25 am

I'm sure many ALS features could be merged into the Rembrandt system, but it's really tricky difficult stuff.


It's technically not that hard, there's at least three people around who for sure could do it, but I'm less sure it can be achieved with a flyable framerate in the end, and I'm also less sure that gives sufficient accuracy at large visibilities (the geometry buffer has limited resolution after all) - so it might be lots of work to get a completely unsatisfactory result.

Anyway, personally I believe 90% of what we're interested in a flightsim can be achieved faster and better in forward rendering - I readily acknowledge deferred rendering solves the last 10% better, but one can burn framerate only once and has to make a choice.

then put the rembrand plane inside the ALS scenery?


Assuming you had some compositing shader that merges the two streams, you'd get to see things like an unfogged plane in heavily fogged scenery or a brightly red lit plane at dawn in a muted bluish lit scenery.

Consistency across the scene is sort of important, if you drop it, the visuals get jarring quickly.
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Re: ALS and Rembrandt

Postby curt » Tue Dec 05, 2017 2:02 pm

The one thing I still *really* *really* miss from the old plib/ssg-based render system is 'real' shadows cast on the ground and on the aircraft. A shadow adds so much scale/depth/position information to an external view (and an internal view) and I really miss having that general purpose feature. Rembrandt brought this back (albeit with some resolution artifacts). I personally think aircraft-cast shadows are a really important feature. For me, it is much less important (but nice) for other objects cast shadows. The lighting features of Rembrandt are incredibly cool, but also less important for a general purpose sim.
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Re: ALS and Rembrandt

Postby Thorsten » Tue Dec 05, 2017 2:48 pm

The one thing I still *really* *really* miss from the old plib/ssg-based render system is 'real' shadows cast on the ground and on the aircraft.


Talk to IcecodeGL, he had this geometry-shader based shadow volume solution which looked sort of promising. I suspect with some pre-processing to get rid of the geometry shader this could even be reasonably fast.
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Re: ALS and Rembrandt

Postby Hooray » Tue Dec 05, 2017 6:31 pm

wow, that's actually much more positive than the typical response you've been posting over the years, suggesting to "search the archives":

Subject: ALS vs. Rembrandt (forward vs. deferred rendering)
Thorsten wrote:I think I have written a combined twenty pages on how I see the relative merits of ALS vs. Rembrandt over time - I suggest to spend some time reading it up as I won't go through the arguments and explanations every time.


(That is one of the reasons why I tend to copy useful stuff over to the wiki to create "pseudo articles", not sure if this ever happened in this case though)
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