answered OBJECT BUG?

[david broome]

After doing some more testing flying low over TE South I am noticing large seemingly random spikes in CPU time to render a frame and huge drops in fps resulting in severe stutter at times.

Generally away from London in the country side my fps bounces usually between 45 and 70 and I only get severe drops when new scenery loading but flying low over London I get between 40 and 55 fps but with huge spikes in CPU usage even while flying over the same scenery.

For example it will suddenly take my CPU 4 times as long to render a single frame and this can result in fps dropping to around single digits to mid teens and severe stutter.

This spiking continues as I bank and circle low over the city.

 

Neither my GPU nor CPU are throttling a far as I'm aware and neither get above 50C

I have 32GB RAM, I5 6600K running at 4Ghz and 1080Ti stock speeds.

I have tried different aircraft from Laminars to paid to free and get the same effect to a lesser or greater degree, it seems fighter jets and hard banking cause the worse cases.

 

Settings are all on high or max with shadows and reflections turned off.

Turning down settings results in higher peak fps but still massive drops to single digits over the city.

 

I'm not sure how much of this might be Xplane 11.3 beta but I have a clean Xplane install on another drive and get the same issue.

Could a dev please test with continually flying low around London city to see if this is reproduced.

I get it elsewhere but it isn't as noticeable as over the city.

 

Thanks.

 

EDIT

 

After more testing I am convinced there is a bug in one or more Orbx autogen objects or something else within the overlay folder.

 

I removed the OrbX overlay folder (B) and reran the sim.

Of course I got much higher fps because only custom buildings were rendered, a smooth as silk 90 to 100 fps.

That meant the custom buildings were not to blame though.

Next I removed the OrbX ortho folder (C) to allow xplane autogen buildings with OrbX custom buildings and my fps was down to around 45 but smooth as silk dipping occasionally to just under 40 or rising to mid 50's.

This means that my CPU or GPU throttling is not the cause.

All this the same settings. 

 

It appears that something within the OrbX overlay folder is taking much more resources than necessary or perhaps has a bug causing performance issues.

I think whatever it is is generated more in cities but also in less populated areas as the same spikes can be had in less densely populated areas just not as severe, perhaps because the object or whatever it is being generated less or fps is already higher in those areas so sudden drops result in less stutter.

[Tony Wroblewski]

Hi David

 

What you're looking at is probably what are called "facade" buildings. These are the irregularly (non rectangular) shaped buildings that require CPU power to render. Basically, when you're flying over smaller towns or villages which mostly just have simple houses or terraces, these are repeated 3D models that are rendered easier by the GPU. However, for complicated shaped buildings such as you'll see in London, these require the help of the CPU, which would seem to mirror what you're seeing here. I'm not an expert on how the internal rendering engine in X-Plane deals with this, but it mirrors what I've seen for years when making heavy use of facades in my free World2XPlane sceneries, and that is you need a good CPU (I'm using an i9 now) to get good performance and throwing a more powerful GPU at it won't improve this. Rumour has it that the change over to Vulkan currently being worked on for XP will start to really help with this, but I suspect we won't be seeing much until early next year on this.

 

The default scenery/autogen doesn't make big use of these type of irregular shaped buildings, but of course the caveat as many P3D/FSX users will know with the autogen is that it is less accurate (Hence why ORBX also have the tech for this platform to do these buildings as well). Sadly it's simply a balance between accuracy and performance, of which we've been trying to find a good balance.

 

 

 

[Fizzelle]

As I understand it David, OpenGL used by X-Plane is not multi-threaded as its pretty old technology that's been patched, upgraded, kicked sideways etc. Which is why Vulkan is being anticipated as it's more efficient, makes use of multiple cores better and makes fewer demands on the system. And it also means that (technically) it'll allow me to use my SLI configuration properly.

 

Although early implementations of Vulkan technology I have tried has left me non-plussed in that I found no meaningful upping of FPS.

 

But it's early days yet.

[david broome]

2 hours ago, Fizzelle said:

As I understand it David, OpenGL used by X-Plane is not multi-threaded as its pretty old technology that's been patched, upgraded, kicked sideways etc. Which is why Vulkan is being anticipated as it's more efficient, makes use of multiple cores better and makes fewer demands on the system. And it also means that (technically) it'll allow me to use my SLI configuration properly.

 

Although early implementations of Vulkan technology I have tried has left me non-plussed in that I found no meaningful upping of FPS.

 

But it's early days yet.

 

Hi, If you mean Xplane 11.3 then Vulkan as yet is not implemented, they are simply rewriting the code in readiness for Vulkan implementation.

Internally this rewrite was enough to give some performance boost but it seems some of these gains from better organised/optimised code got lost in the final build.

Vulkan itself is expected to be implemented 1st quarter 2019, possibly 2nd quarter as the code is not fully converted yet to make use of Vulkan API.

So fingers crossed we get proper multicore support and optimised use of multi-threading soon, something Xplane has long needed.

 

[david broome]

8 hours ago, tonywob said:

Hi David

 

What you're looking at is probably what are called "facade" buildings. These are the irregularly (non rectangular) shaped buildings that require CPU power to render. Basically, when you're flying over smaller towns or villages which mostly just have simple houses or terraces, these are repeated 3D models that are rendered easier by the GPU. However, for complicated shaped buildings such as you'll see in London, these require the help of the CPU, which would seem to mirror what you're seeing here. I'm not an expert on how the internal rendering engine in X-Plane deals with this, but it mirrors what I've seen for years when making heavy use of facades in my free World2XPlane sceneries, and that is you need a good CPU (I'm using an i9 now) to get good performance and throwing a more powerful GPU at it won't improve this. Rumour has it that the change over to Vulkan currently being worked on for XP will start to really help with this, but I suspect we won't be seeing much until early next year on this.

 

The default scenery/autogen doesn't make big use of these type of irregular shaped buildings, but of course the caveat as many P3D/FSX users will know with the autogen is that it is less accurate (Hence why ORBX also have the tech for this platform to do these buildings as well). Sadly it's simply a balance between accuracy and performance, of which we've been trying to find a good balance.

 

 

 

 

Than you Tony, that makes a lot of sense.

I figured it was more likely a bug than a bottleneck because of the huge drops I was seeing but as you say, given the CPU in Xplane is already being flogged this might just be a symptom of it being sent over the tipping point.

 

I will continue to experiment just in case there is an edge case facade causing the issue rather than a general overwhelming of the CPU with multiple facades since I don't have this issue with other complex city scenery (and my CPU isn't a complete potato ) and report back if I find anything specific now that you have narrowed the field.

 

Thanks for all your great work on what is a fantastic scenery addition to Xplane.

 

[david broome]

Tony or admin you can mark this as solved thanks.

I made another clean install and did more testing and it seems it is certain aircraft (fast jets or maybe just some 3rd party aircraft) that are part of the issue.

With objects maxed out I do only get between 35 and 40 fps but still get smooth fight with default prop aircraft.

If I turn objects down to high I get between 45 and 55 fps and very smooth flight with prop aircraft.

If I use fighter jets on max objects and bank hard it causes stutter, on high I still get some stutter but not as bad.

 

I noticed that my fps is more volatile flying 3rd party aircraft (payware) and generally they are more demanding so perhaps a combination of fast aircraft, many custom facades and max objects just sends my CPU past its breaking point.

I think there may be something else I have messed up with my old install though as the stutter was very severe at times with fps crashing into low teens or single digits for moments and bouncing back up to 50 fps at others.

Moral of the story, "if it ain't broke don't fix it."

 

Thanks for your guidance Tony and good luck with the night lighting and other fixes.