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A persistent cloud problem...

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Hi Pete! First off let me thank you again for adding the helo trim function to fsuipc, that was simply superb! Cheers. :)

Anyway, I have a question regarding a problem with cloud rendering in FS that I was hoping you might have some insight into. I doubt that FSUIPC is in any way responsible for this issue as I removed the DLL and no improvement was seen, so please feel free to ignore this post if you're busy! If anyone else can shed some light into it though, please do. :)

It is related to a much older post on this forum, for which a cause or solution were never discovered. I've discoverd the cause at least.


The problem is an intermittent drop in framerate when clouds are present. Whether created by an addon program like activesky or coming from FS's own weather, global or locally set, it makes no difference. When flying at high speed, every minute or so, if clouds are ahead, I experience a severe drop in framerate. The cause of this, which the previous poster didn't catch I think is that FS "fades in" clouds as they come within view distance. This process of inceasing the alpha value of the polygons the clouds are textured onto takes roughly 15 seconds. It fades them in as square shaped tile sections in pretty much the same manner that scenery tiles are loaded it seems. It's during this fade in that the frames per second just plummet, but only *if* that particular section of clouds is visible on screen as they materialize. The second the clouds have finished their alpha transition from invisible to opaque, the fps jumps back up to normal. If more clouds are present over the horizon beyond those ones, the process repeats roughly a minute later, depending on velocity of course.

This is easily testable if you have a track-ir. These drops in fps only occur when looking forward in the aircraft. As soon as a section of clouds starts to fade in and the fps drops, if you quickly look to the left or right, so that those particular clouds are no longer visible, the fps jumps back up to normal (regardless of how dense the clouds all around you are). Look back towards them, and if they haven't finished fading in, you're back to a slideshow until they do. I know for a fact it is this fade in process that causes the drops in framerate. It does not occur when flying from a heavy cloud area into clear air. The denser the cloud section being loaded into view (ie: heavy overcast) the lower the frames go during this time. Whether this is unique to ATI cards, or affects everyone, I have no idea, but the poster in the link above had an Nvidia I think. I'm guessing this is a basic part of the dynamic weather system that isn't defeated by setting weather change rate to 0.

So my question for you, and anyone else: Is there a way to simply force cloud sections coming into view on the horizon to pop in all at once instead of gently fading into view? I'd much rather see a minor graphical anomaly on the horizon for a second than a 20 fps drop for 15 seconds every minute or so. I know the FS weather engine *can* do this, because anytime you use an external weather program, all local weather simply pops into view at once the moment the program has finished sending the data to FS. Its only when you want to go somewhere that the slideshow begins. ;) The reduction in framerate from this phenomenon is pretty nasty, from around 35 fps (my norm at 1600x1200 with maxed everything) to around 5-10 fps, unless I stare out the left window for a minute until it's finished, hehe. Seems like a small process to hog so much in the way of resources, but it brings my machine to its knees every time, and results in the famous blurries for another 30 seconds as everything tries to catch up, haha.

Has anyone else run into this?

Thanks again Pete!

Take care.


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The problem is an intermittent drop in framerate when clouds are present.

I don't get such problems, but then I have a very fast system with a fast graphics card. You need to adjust the cloud draw distance (actually letting them draw when they are further may even help, oddly), the cloud density, and, above all, 3D clouds only -- those ugly 2D clouds are drawn suddenly ("popping up") in a ring around the aircraft and cause awful stutter.

Just play with the settings in FS till you get smooth results. Don't look at the frame rate, just fly and see if it feels smooth, that's all that matters.

So my question for you, and anyone else: Is there a way to simply force cloud sections coming into view on the horizon to pop in all at once instead of gently fading into view?

Well, I would absolutely *hate* that, but the only thing I can think of is to set the cloud draw distance as low as possible. You won't get any clouds on the horizon at all then (unless you are on the ground, so the horizon is too near! ).

I'd much rather see a minor graphical anomaly on the horizon for a second than a 20 fps drop for 15 seconds every minute or so.

Blimey! I've *never* ever experienced anything like a 20 fps drop (this would make my frame rate less than 10 in most places, negative in some)! What on Earth have you got your frame rate limiter set to? Use something sensible like 25 or 30 fps as the limit and let FS use the rest of the time, when it has any, getting its graphics and textures sorted.

Also, go get some of the more compact cloud bit maps. I don't remember the names, but they do help a lot.

Has anyone else run into this?

No one I know of. You might want to post on the FS2004 Forum, or enlist the services of that competent company who sort out FS performance, especially graphics, with you. FSGS is it? Ah yes, near here:

FSGS Support Forum

Official support forum for "Flight Simulator Graphics Solutions". Drop in with questions, answers or just for a general discussion.




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Hi Mike,

A few things:

1. If you are using Active Sky, weather should not be popping in and out after an update. We designed Local Suppression to prevent this.

2. Lock your FPS to 25-30.

3. Set your Cloud Draw Distance to 30 in FS04.

4. What are your system specs and what else do you run with FS04?

5. What are your AA and AF settings?

6. Are AA and Render to Texture off in FS04?

7. As Pete suggested you may want to try lower resolution clouds.

8. Lock your maximum visibility to 29.

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Hey, thanks for the quick replies Pete and JSkorna! You're fast. :)

Here's a bit of info on my setup etc. Didn't want to post it in the last message as I felt it was turning into something of a book hehe.

AMD 64 3400+ 2.2ghz, ATI 850XT 256mb, 7200 rpm sata drives, 1 gig of ram, and all the usual bells and whistles, track-ir, controllers etc. I fly at 1600x1200 with AA and AF completely off. At that resolution they add nothing and simply knock down my average fps, and in my opinion they degrade image quality in FS anyway. A little bit of shimmering in the extended texture ring doesn't bother me in the slightest. Last bit about me, is that I've worked in the games biz as a 3d artist for 10 years, with EA, Namco, and a couple other small developers, so I'm no stranger to messing about under the hood with textures and rendering engines hehe, but this one really has me stumped.

Normally this machine just smokes FS completely. I run with max settings on everything, clouds, scenery, you name it. I have the fps locked at 30 normally. If I toss it up to unlimited I'll see fps jumping over 80 but of course that will introduce microsutters with heavy sceneries, and I prefer a little smoother ride. Even flying over seattle, with UT, 3 layers of overcast, some cirrus and maxed out traffic, the fps counter never drops below 29.5. Its rock solid in all cases, except, yup, when new clouds are fading in on the horizon. When AS is running I've tried putting in all manner of suppression ranges, from 100-500nm, and it makes no difference in this cloud fade in stutter. Doesn't matter if I shut down AS after it loads in weather either. Its definitely not AS that's causing this. I get this effect using FS's own weather as well. I've done some tests with it, basically cranking view distance to max, turning off all view distance reductions in fsuipc and AS, flying up to 35000 feet over an overcast layer, and then saving the flight. Removed fsuipc, shut down AS, restart FS, load flight, and then watching new clouds start to fade in at 80nm distance, the FS max. As soon as new clouds begin to fade in, as they cross the magical 80nm vis barrier, poof, frame rate drops to single digits for roughly 10-15 seconds. So both of your wonderful products are in no way responsible for this. :) The heavier the section of clouds fading in, the lower the fps goes, but it is for a fixed period of time. It's always 15 seconds, which seems to be how long FS thinks new clouds should take to come into view. However this only occurs if those clouds are on screen as they go through this process. If I glance away from them, framerate shoots back up to normal. If I am watching them as they do this, the second they're finished fading in, framerate jumps back up to 29.9 solid. I've tried using reduced cloud texture sizes, down to 64x64, tried both dxt3 and 32 bit, no difference. I've tried it with render to texture on and off. Leaving render to texture "Off" of course will cause the game to crash if using dxt3 clouds (its an ATI thing). Again, no difference.

I've tried dropping the max vis to 60nm and setting the cloud vis out to 80, so that they might come into existence without being rendered at first, since they're beyond the clipping plane. Again, no effect. I normally use 100% 3d clouds. I've tried dropping them to 50%, with the rest 2d impostors, but they still fade in at a certain distance, making that transition from 2d to 3d, and the fps drops.

I'd love to try this problem on an nvidia card, as I have a hunch this might be some sort of bug in ATI's catalyst drivers, but alas I don't have one available.

I've been using and tweaking FS2004 since the day it came out, but have never managed to beat this problem, always just sort of put up with it. It exhibited the same behaviour on my old radeon 9800 as well. Could be some VIA drivers issue as well, haha who knows. Maybe it only affects my system and the system of the poster I linked in the previous message. *boggles!*

Thanks guys!


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Hey, sorry for the late reply, didn't have any time to FS this weekend. Anyway, I set the cloud draw distance down to 30nm. Same behaviour exactly. I can watch them fade in and the fps drops from 30 solid to around 12 for 15 seconds. When the fade in is complete, jumps back up to 30. Haha. What a silly problem eh.

Thanks for the help though!


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Hi Mike,

Something is not right on your system then. The fade-in is normal and at that point they are drawn in full resolution. But the FPS hit for such a long time is not normal.

I can suggest looking at:

A DirectX problem. Does running dxdiag turn up anything? Can you run the spinning cube tests well? They should all spin fast.

Motherboard drivers including AGP. Is you AGP set at the correct speed?

Video drivers with a driver cleaner in between such as Driver Cleaner Pro, a freeware program.

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Hey JSkorna. Thanks for the suggestions. I tried them all but to no avail sadly. Installed the latest via chipset drivers, cleaned out the ati drivers and reinstalled the latest. Dxdiag shows all tests work perfectly, cube spins smoothly. Agp is at 8x. I leave fastwrites off normally. FS never complains about FW being on, but other games do on occasion. Turned fastwrites on to test, and no change there either. Thanks for all your time though.

I've put up with this bug for years, just recently decided to have another go at cracking it and thought I'd see if anyone else had run into it. Its probably moot in the end since FSX is just around the corner, hehe. I'll be first in line at EB the day it arrives, cloud stutters or not. :)



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