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Rembrandt Heavy FPS Drop (AMD)?

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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Rembrandt Heavy FPS Drop (AMD)?

Postby turtle » Sun Mar 27, 2016 7:20 pm

I have a R9 Fury (Strix Edition) which I consider should be able to run FlightGear with all the eye-candy just fine. However, when I launch the simulator I am getting 20-25 FPS in it's default configuration. I went ahead and turned off Rembrandt, and now I am seeing 50-60 FPS.

I'm curious to know if this is an AMD or Nvidia issue, or just Rembrandt being tough to run in general?

I might be getting a new graphics card this year, so I want to know what I will be losing with FlightGear before I buy.
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby PINTO » Sun Mar 27, 2016 7:22 pm

Rembrandt is just tough in general. I have a GTX960, and it hits the frame rates pretty hard for me unless I turn shadows way down.
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby Hooray » Sun Mar 27, 2016 7:37 pm

A while ago, Richard came up with the hypothesis that this could be vsync related - note that Rembrandt is using multiple offscreen (background) cameras that are rendering to different buffers (textures) - and it seems that these offscreen cameras are also vsync limited (unnecessarily). For some background info, see:

http://wiki.flightgear.org/Vsync
http://wiki.flightgear.org/FlightGear_N ... _and_Vsync
http://wiki.flightgear.org/Project_Rembrandt

Otherwise, is is true that Rembrandt, in its current form, is generally considered to be unusually "heavy", even by people with otherwise state-of-the-art hardware (gaming laptops, multi-gpu setups etc).
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby Richard » Sun Mar 27, 2016 8:30 pm

turtle wrote in Sun Mar 27, 2016 7:20 pm:I have a R9 Fury (Strix Edition) which I consider should be able to run FlightGear with all the eye-candy just fine. However, when I launch the simulator I am getting 20-25 FPS in it's default configuration. I went ahead and turned off Rembrandt, and now I am seeing 50-60 FPS.

I'm curious to know if this is an AMD or Nvidia issue, or just Rembrandt being tough to run in general?

I might be getting a new graphics card this year, so I want to know what I will be losing with FlightGear before I buy.


Rembrandt is harder work for both the GPU and the CPU, and this goes up exponentially with the amount of geometry. However on my R9-290 the report that Hooray referenced shows that vsync is making this worse. This could just be the drivers on my system, or an OpenGL / OSG strangeness. The basic problem is that OSG is waiting for a vsync for each camera, which hits rembrandt hard as it has a lot of cameras.

However you will get faster frame rates, better lighting, cloud shadows, trees that move in the wind and a whole heap more features using Atmospheric Light Scattering (ALS) rather than Rembrandt.

Rembrandt (deferred rendering) really is about emissive lights, the ability to do shadows within deferred rendering is more suited to much smaller fields of views. The shadows usually flicker around the edges in a cockpit view (less noticably externally).

At the moment I'd say that ALS is the way to get the best looking visuals. ALS works best with detailed weather (aka. advanced or local weather). There are some extra shader settings on the configuration for detailed weather.

There are other problems with AMD graphics cards (I can't use point lighting and often the text in dialogs / menus flickers). This is probably a driver problem.

I'd generally recommend nVidia kit for FlightGear simply because most of the develoment team use it.
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby Hooray » Sun Mar 27, 2016 8:48 pm

The main reason why nvidia-based hardware is usually used, and in fact recommended, by FlightGear developers/contributors is due to the fact that most contributors are based on Linux-like operating systems, and that's where Nvidia hardware/drivers would simply work, and even shine, in comparison to ATI/AMD or Intel-based GPUs. Note that this is despite the nvidia drivers being closed-source/proprietary, and despite ATI/AMD drivers being available as open source.

The situation has somewhat improved lately, but usually, nvidia still remains a surebet for people wanting to use OpenGL/GLSL on Linux, whereas even the proprietary AMD/ATI drivers on Mac OSX are known to be problematic more often than not.
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby erik » Wed Mar 30, 2016 10:35 am

I've seen test at Phoronix that for Vulkan the difference is much smaller between NVidia and ADM/Ati so there's hope for the future. But how soon this future will come for FligthGear is still unsure, since there has been some tinkering with Vulkan for Open Scene Graph but nothing serious yet.

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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby Müller » Wed Mar 30, 2016 1:21 pm

Do not expect a super frame rate even using a Nvidia, previously I had a HD6850 and ran cool the FG and now I have a GTX970 SuperClocked and FG works between 50 and 60 fps, sometimes reaches 61fps, but for one or two seconds perhaps a mistake, I do not know.
I did a little test on the Space Shuttle my fps were in the cockpit between 30/40.
The result is bad? certainly not that I think not bad, but not great results.
The tests were with Rembrandt off, and at airports not very populated.
I do not use Rembrandt, or rarely use, maybe I'll do a test to see how they fps but will certainly work well above my old HD6850, who Rembrandt was around 20 or less fps.
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby jaxsin » Wed Mar 30, 2016 1:27 pm

I am thinking out loud here, but blender under linux uses NVIDIA CUDA for rendering optimization. There are also a few other programs that use this CUDA, aircrack-ng as an example. I do not think you will get much advantage from the newer NVIDIA cards unless you run optimization for CUDA??? I also, without much thought, think rembrandt would benefit most from this. Rembrandt is similar to how blender render images, no?
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby Müller » Wed Mar 30, 2016 1:35 pm

FG does not seem to "like" latest Nvidia GPU and perhaps also AMD.
But as I mentioned, I do not consider as bad results
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby Thorsten » Wed Mar 30, 2016 3:00 pm

I did a little test on the Space Shuttle my fps were in the cockpit between 30/40.


On a GeForce 670M I'm getting a solid 60 fps like a clockwork in orbit. Close to the ground according to whatever the terrain demands. The cockpit is heavy, but no challenge for a modern GPU, whatever drags your framerate is elsewhere.
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby Müller » Wed Mar 30, 2016 5:46 pm

whatever drags your framerate is elsewhere.
possibly, probably.



As I said above, not bad fps, and one thing I understand you do not need to run at 100fps to get a good result, 40fps is very good.
I play Tom Clancy's Rainbow Six Siege with frame per seconds over 100 and I see no difference between playing with 40 or 100 fps.
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby Müller » Wed Mar 30, 2016 7:08 pm

On a GeForce 670M I'm getting a solid 60 fps like a clockwork in orbit.


but here do not appear solid 60fps, but 10 to 15 fps http://forum.flightgear.org/viewtopic.php?f=4&t=25747&start=840#p262051
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby Thorsten » Thu Mar 31, 2016 4:57 am

Did the idea that I have different setups occur to you? :-) As you may note, Earth also doesn't have hires textures in that series, whereas sometimes it has.
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby jaxsin » Thu Mar 31, 2016 12:04 pm

Müller wrote in Wed Mar 30, 2016 7:08 pm:
On a GeForce 670M I'm getting a solid 60 fps like a clockwork in orbit.


but here do not appear solid 60fps, but 10 to 15 fps http://forum.flightgear.org/viewtopic.php?f=4&t=25747&start=840#p262051


I got a 700 series Nvidia card and I can't hit 60 fps with quality 4 default Cessna at default KSFO. I see ~15 fps. If I load up at say my local airport KELM, I get 45 fps inside cockpit and near 60 fps outside. I think I run pretty standard settings. I do like my MSAA and texture filtering though. There has been talk about random veg shadows on development list to improve performance. I don't even use random veg shadows :(
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Re: Rembrandt Heavy FPS Drop (AMD)?

Postby Müller » Thu Mar 31, 2016 12:50 pm

For me it is not worth to continue writing about frame rates and other things, just search a bit the Forum on these issues and many others, but I say this:
I congratulate those who can run FlightGear with 60 fps.
And those who run with 10 or15fps have a little patience because I believe that one day this will improve with the development of the simulator, and we have a passion for FG that makes us overcome these details, I think this says it all, dedication, efforts to do a better simulator every day.
Congratulations to the whole team of developers who are volunteers and are brilliant at what they do, work and provide their time free so we can all enjoy a great flight simulator.
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