GP Line flicker

Gaiiden

FSDevConf team
#1
I'm getting flickering of GP lines - around 2,000 feet up it is really noticeable for some of the thicker lines I'm using for runway edges (2-4ft). The 1ft yellow taxi lines are too small to really notice the flickering but it's there if you look closely. I've tried two textures that came with ADE 1.6 and am also using the default taxi markings texture and they all flicker. I'm running a Radeon 7970. AD3 file attached
 
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gadgets

Resource contributor
#3
I've compiled and installed your airport on my system. No flickering of the "z-fighting" type .

Flickering is due to two objects of similar orientation very close together. Ground polys are drawn at the ground elevation at their reference point. If you compile your ground poly as a single group, then the reference point is the ARP. If you compile in multiple groups, then the reference point will be closer to the GP objects. Obviously, if your flatten is not set to your ARP elevation, you COULD have flickering. (You did not attach your airport flatten, so I couldn't check that).

Another symptom that you might be interpreting as flickering (but is quite different) is a ground poly object going in and out of view depending on the viewing angle. This is most frequently observed with FSX and appears, in part, to be machine related. There are numerous posts in this forum on the topic.

Finally, if you review the posts in the fsDeveloper forum re flickering and ground polys, you'll find a few that suggest this type of flickering may video-card related. My recollection is that this was speculation. I don't recall conclusions.

Bottom line, I'd check the flatten and ensure its edges are well away from any ground polys.

Don
 

Gaiiden

FSDevConf team
#4
my airport flatten should have been in the AD3 file (hidden). Regardless, it is set to the same height as the ARP. It does hug the runways and taxiways pretty close though so I will try to move the edges further away. I will also play around with the compiler options to see if that does anything. I'm aware that this issue could be video card related which is why I specified I'm running an HD7970 in case anyone with that hardware can try to reproduce.

Flicker? Or Shimmer?

Different causes
No idea what the difference is visually between the two. The whole line doesn't blink in and out, but lots of little pieces of it do along its length. It's similar to the effect I see for some BGL texture objects I place on the ground that I need to elevate like 0.3ft to prevent them from "tearing" at higher altitudes (the Z-order effect)
 

gadgets

Resource contributor
#5
If your AD3 file contains a valid flatten, I would have expected ADE to have generated a CVX file for it. It didn't.

Don
 

Gaiiden

FSDevConf team
#6
very odd. I just deleted my CVX file and recompiled and a new one popped up. It's there for me don't know why it wouldn't be there for you in the AD3 file I attached.

Anyways, I stumbled across a solution. My runway intersection looks like this in real life. Since the thinner edge lines would end at the thicker ones, while playing around with textures and compile settings today I thought to make the thin ones layer 39 so they would rest under the thicker line's layer 40 and create a more seamless look. I noticed that the thin lines no longer flickered but the thick lines still did and played around with compile settings a bit more before I realized after seeing no effect that it was the layer setting. I changed the thick lines to layer 39 and the thin ones to layer 38 and the flickering was completely gone from all altitudes and angles.
 

gadgets

Resource contributor
#7
Curious! Something in your airport (or that is affecting your airport) is conflicting at Layer 40. This has not been reported before, but I'll keep it in mind should anyone report similar difficulties. (I see nothing in the ADE file that should cause this.)

Placing the lines in different layers should not have any effect. With ground polys, layering is used so as to be able to control which texture gets placed on top of another. The GPs all get placed at the same elevation and can be superimposed in a single layer.

Re the CVX file, first of all, I note that the flatten elevation is 56.997m while the airport elevation is 57m. While this difference won't materially affect the appearance of the rendered airport, it may be enough to cause GPs to disappear at certain angles.

Also, since the flatten IS in the ADE file (hidden, which is why I didn't see it yesterday), I spent a little time exploring why it didn't compile for me. What I discovered is that, if I compile the airport for P3Dv2, the flatten is generated. But, if I compile for FSX, I get an error message "The system cannot fine the file specified" and the CVX file is not generated. I ignored this message yesterday, assuming it pertained to some model placed in the file. Apparently, it relates to CVX file generation. Over to you, Jon.

Don
 

Gaiiden

FSDevConf team
#8
regarding the flatten, might be something in the project since I compile for FSX?

The ARP and flatten elevations match for me at 186.998 feet. There may be a slight calculation inconsistency with decimal places or something when converting to meters?

As for layering, there is indeed an effect even if it is only slight I consider it worthwhile. See the attached image - the larger runway runs over the smaller one and the textures are layered to show this on the top circled intersection (fat line layer 39, thin line layer 38). The bottom circle the textures are on the same layer. I even had to delete the larger runway and then undo the action in ADE to get that runway texture to draw atop the smaller runway
 

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gadgets

Resource contributor
#9
regarding the flatten, might be something in the project since I compile for FSX?
I'll leave that to Jon.

The ARP and flatten elevations match for me at 186.998 feet. There may be a slight calculation inconsistency with decimal places or something when converting to meters?
If you display in meters, there is a difference. With the flatten being lower than the airport, it probably won't matter. If the flatten were higher, it might. (I suspect Jon saves these values in meters, so what you see in metric is probably "what you get".)

Jon, if both conversions were done by ADE, shouldn't the converted values be identical? (This may be the root cause of, or a contributor to, GPs disappearing at some viewing angles.)

As for layering, there is indeed an effect even if it is only slight I consider it worthwhile
That particular texture has an alpha channel to facilitate "texturing". That's why you are seeing differences. Without the alpha channel, there SHOULD be no difference. (But layer numbers are cheap!)

Don
 
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