Strange FSX file accesses....

[LuisFelizTirado 33]

4.5LOD radius setting: - Low = 2.5 quadrants - Medium = 3.5 quadrants - High = 4.5 quadrantsThis slider indicates how much vector terrain and ground textures should be initially loaded prior to flight.By the way, a setting of 4.5 will, in the worst case, lead to loading about 358 MB of vector terrain and textures. Some foolish people attempt to increase this value in the cfg file - for example, setting to 8 will cause the system to attempt loading over 1.1 GB of vector terrain and textures! Not something you want to do.So, if you are loading scenery on the other side of the planet, try setting LOD radius down to a lower (lowest) value and see if the problem persists.Some scenery elements cover different QMID (quad mesh identifier) levels as already mentioned. In addition, some types of scenery bgls contain multiple LOD levels within the same bgl (LOD and QMID are basically the same thing - LOD+2=QMID). For example, the new FS X-style photo scenery can contain all the different LOD levels in the same bgl, thus improving performance, since they do not have to be calculated and rendered at run-time. The same thing goes with altitude mesh bgls that now have all the necessary LOD levels in the same bgl. (In FS9 and previous, we would often included multiple bgls, each having a different LOD level for the altitude mesh.)The above explanation does not mean that Phil's answer is particulary clear to me. For photo-scenery to be loaded from the antipodes would mean that it has something like LOD 2 in the bgl, and as far as I know, nobody makes photo-scenery like that. (Generally, my photo-scenery goes from LOD 6 to LOD 16 or 17). So, does this problem mean that there is some old-style scenery that covers very large quad levels, and what are they?What nobody who complains of this has so far taken the trouble to do is examine all the scenery that is loaded when it is so far away and determine what kind it is - NAV? Objects? Photo-scenery? and if so, FS X-style or FS 9-style? Altitude mesh?Nor is it very clear if the scenery is being loaded, which could very well cause stutters, or if it is only the scenery database that is being queried. This last would be quite normal since the scenery engine must determine when new scenery should be loaded, so when moving or changing orientation, the various scenery database elements should be queried. Normally, a few thousand queries would not impact performance, particularly on processors with Giga-cycle speeds.This sort of information would help tremendously to figure out the correct solution.Best regards.Luis

[Gypsy Baron 10]

Thanks for the replies and clarifications, Martin and Luis.I'm in and out today and tomorrow but will do some further investigationand testing to try to get a handle on what is going on.I also want to do some BGLAnalyze operations on some of the manyfiles I'm seeing read. Particularly those with names that implythat they are specific scenery objects located at a distant airport.And Scott, that type of architecture is what I would like. I don't want to have to co-mingle BGL's and textures from diferent airportsor scenery areas in a particular region to get to a single mainfolder, scenery and texture folder for a blanket enabledisable operation. Paul

[Bert Pieke 7,584]

I'm really confused now. Are there two instances of "4.5"?A while back, the issue was the relatively tight ring of high detail textures visible from the cockpit. The answer then was that 4.5 tiles got loaded at LOD radius of high.Now, we are trying to understand loading of scenery files from halfway around the globe, and again the answer is: 4.5 tiles get loaded.Are these the same 4.5 tiles, or is this a coincidence?

[PhilTaylor 45]

my reply wasnt as much an "answer" as an attempt to set context via referring to the SDK. the information is freely available to all who have a Deluxe Edition and update the SDK as they install the SPs.I agree that digging in is required, what I dont agree with is a priori assuming this means there is something wrong. or that our code is bad, or that our QA failed. and yes, we have seen scenery authored where loading Japan when flying in the UK is not anomalous. the case where NZ was being loaded when flying in the UK was anomalous and that we did put a fix into SP2 for.

[PhilTaylor 45]

I dont remember the visible from the cockpit issue. as Luis states, the extent of loading depends on LOD. I am assuming most have it set to high, hence my use of 4.5. it is a worthwhile experiment to vary it and see if that makes a difference.the geographic extent in miles/km of a "tile" depends on the LOD/QMID that the scenery is authored at. there is no 1 answer.to determine geographic extent at a certain LOD/QMID is not that hard. take the images I posted. the earth is roughly 24k miles circumference at the equator. count the number of square boxes in that image, that is the number of tiles at the equator at that LOD/QMID. divide 24k by that number, you get the rough geographic extent in miles for that LOD/QMID.

[Bert Pieke 7,584]

Phil, let me try this again...In the discussions about the "blurries", you published a paper with many screen shots showing texture detail at various zoom levels, and at various LOD levels: low, medium, and high."High" corresponds to lod_radius=4.5 in fsx.cfg.My question is: is that the same "4.5" that we are discussing here with file loading, or is this a coincidence?

[PhilTaylor 45]

its the difference between mesh-bgl/scenery loading, and blurries/texture loading.I do reference LOD in the 1st blurry article as a factor that influences texture resolution and may help influence Type 3 blurries. the blurry article says nothing about scenery or bgl, though.I just searched the PDF and find no occurrences of 4.5. The occurrences of tile that I find are where I define the 4 types of blurries:"1. Blurries across a lot of tiles with photo-scenery (especially FS9-style photo-scenery that uses 1km small bitmaps, which can require a lot of file accesses to generate one terrain texture ). These eventually catch up.2. Blurries across a lot of tiles with default scenery and a variety of settings and cards, which eventually catch up.3. Blurries with either style scenery, where it appears some tiles are just a little blurry all the time.4. Blurries where all ( or most ) tiles are blurry all the time"which refers to terrain texture tiles, since the context is blurries and not scenery loading.In the 2nd blurry article, I likewise find no occurrences of 4.5. In a similar fashion, the reference to tile is wrt either TileProxy or a terrain texture tile and blurries. Not scenery, not bgl.yes, the same LOD and tile terminology is repeated. and yes the LOD influences load range for mesh and texture.it is the same engine after all, and terrain textures drape over the mesh, so the terrain textures use the same hierarchy mechanism in a parallel manner on top so to speak. they wouldnt line up otherwise. and it is the mesh polys that own the uv coordinates that control the texture mapping so this leveraging of the same hierarchy description/mechanism in both places ( mesh, texture ) is natural and expected.however I think the context is pretty clear in each of these discussions ( blurries is texture, scenery loading is mesh/bgl ), so there should be no confusion about what we are talking about in each case.

[PhilTaylor 45]

so I thought of a way to lay this out so the reuse of the LOD might make sense without getting too deep.if you consider a mipmap texture chain as a vertical extent all the way from a 1x1 texture to a 1024x1024 texture, then this analogy might help:for mesh/bgl - LOD translates to more horizontal extent across the ground loaded for texture - LOD translates to more vertical detail in the mipmap chain by changing the max mip level used.so LOD for mesh goes lo=2.5 tiles,med=3.5 tiles,hi=4.5 tilesLOD for texture goes lo=256x256, med=512x512, hi=1024x1024and by changing what texture resolution max is used that is how textures use of LOD influences blurries.does that help?

[cklink 0]

That one still bugs me - and its not a blurry issue, it's the "unadjustable" LOD rings. No matter what, those rings are fixed and move with you. It's not the scenery need's to catch up (you can sit in slew all day and those resolution rings won't change), it's that the distances in which the resolution drops is fixed, and no config parameter will change it. (I sure wish there was)I posted about this before here ..http://forums.avsim.net/dcboard.php?az=sho...ing_type=searchRegards'Garetthttp://forums.avsim.net/user_files/185139.jpghttp://forums.avsim.net/user_files/185140.jpg

[Bert Pieke 7,584]

When I select "high" for Level Of Detail Radius in the FSX scenery settings, the fsx.cfg file creates a line:lod_radius=4.5 under terrain.This is the 4.5 I refer to...Just to see if I understand what you are saying..Detail terrain close in (texture)and geographic area (mesh/bgl)are linked/related and are both influenced by this one setting.Setting this setting to high in fsx accomplishes:1. extending the ring of detail terrain (to some distance)2. extending the geographic area where scenery is loaded (to 4.5 tiles) and these two things go hand in hand.

[Bert Pieke 7,584]

Phil, thanks for taking me through this, one step at a time.LOD for texture (256x256, 512x512,1024x1024) sounds like the Max global texture resolution slider in FSX.. or am I totally mixing things up now?

[LuisFelizTirado 33]

The QMID (quad mesh identifier grid) is just a simple system of quadrants that progressively get smaller and smaller. Start with one quadrant, then partition it equally in 4 parts, then partition each of those parts into 4 more, and so on.Here is a table of the extents of the different qmid levels (the different size grids):http://forums.avsim.net/user_files/185160.jpgAll of this information is in the Terrain S.D.K., although it does take a while for it to sink in.What is the purpose of the QMID grids?All scenery could just be in one very big file, and when flying, the computer could just attempt to load 10 GB of data at once. But, this is not very efficient, or even possible for the moment. So, all the scenery is broken down into chunks according to a geographical grid, the QMID. These are the limits:4 - corresponds to some of the data files like NVX (nav aids), ATX (airways)7 - corresponds to the individual APX (airport) OBX (obstruction), BRX(bridge), CVX (vector) data filesThis way, the scenery engine only loads data needed for the flight.The LOD radius slider (LOD is the same grid, now named QMID) simply determines how many geographically limited files are loaded:Low = 2.5 quadrantsMedium = 3.5 quadrantsHigh = 4.5 quadrantsWhy the half quadrant? I don't know, since the FS developers don't tell me their secrets, but I suppose that we should imagine ourselves in the center of a quadrant, therefore half-way from its limit, then count from there.The size of the quadrant depends on the type of scenery and how large a grid it uses - normal terrain is quad 7, NAV is quad 4.Photo-real ground textures and altitude mesh have a different arrangement in FS X, making them much more efficient than FS 9 photo ground textures. The bgl contains multiple LOD levels, that is, different levels of detail, or resolution, the same as can be found in the normal default ground textures:http://forums.avsim.net/user_files/185161.jpgSo, there are multiple images in the bgl with different resolutions (which is all that LOD or QMID are in reality).So, how can you fly Tokyo and load London?Let's take a look at an example, photo ground textures of Gibraltar:http://forums.avsim.net/user_files/185162.jpgThe bgl contains image with resolutions from LOD 6 (626 meters per pixel) to LOD15 (1.2 meters per pixel).The scenery engine will presumably load the lowest resolution first from a distance, then progressively higher resolutions as we approach the scenery. But, let's consider the lowest resolution LOD 6 image - this corresponds to a quad 8 grid:http://forums.avsim.net/user_files/185163.jpgWe can display the grid in TMFViewer:http://forums.avsim.net/user_files/185164.jpgThe scenery is pretty small compared to the grid size. You can also load the DEM file like Phil suggests, but I use the image_globe files - it is all the same:http://forums.avsim.net/user_files/185165.jpgAnd let's pull back and see how much is covered by 4.5 quadrants at quad level 8:http://forums.avsim.net/user_files/185166.jpgSo, flying within that area will mean that the LOD 6 image of the Gib scenery will load even if we are in Tunisia or Basque country, that is, pretty far away, if LOD radius is set to High (4.5).Since I consider myself a pretty smart fellow (just like everybody else here), I always set my LOD radius to 2.5, thus limiting the loading of distant scenery.What does it take to fly in Tokyo and load London, then? The photo textures would have to include LOD 2 resolution images (quad 4 grid), and we can display that in TMFViewer:http://forums.avsim.net/user_files/185167.jpgAnd then count the quadrants from Tokyo to London:http://forums.avsim.net/user_files/185168.jpgDoesn't quite make it, and anyway nobody would make photo scenery like that, since the LOD 2 resolution image would be just some solid blob of color with no details at all. So, this seems highly unlikely.So, why are people reporting distant scenery being loaded? Good question, and forgive me for repeating:Is the scenery being loaded, or are the scenery files only being queried by the scenery engine? There is a difference, and the queries are normal procedure - the scenery engine must query the files everytime you move or change orientation since it does not know where you intend to go and it must be ready to load the scenery before you get there.This is pretty important to determine, and there seems to be some confusion in the use of FileMon, so please be specific and indicate whether the files are loaded or just queried.Best regards.Luis

[Guest JeanLuc_]

I certainly hope Phil will clarify this. I certainly hope texture resolution is not dependant on number of tiles loaded around you. You should be able to have high res textures no matter what, unrelated to the level of detail of the tiles (mesh-wise) around you.

[Guest JeanLuc_]

I've noticed that as well since FS8 at least: the algorithm to switch from one mip map to the other is making "visible" bands of texture resolution. I remember a while back, playing games like Quake2, when there was an option for the blending of mipmaps (maybe it was a feature supported by OpenGL and not DirectX). This permitted to have say: mip1 - blend of mip1/mip2 - mip2 etc... instead of mip1 - mip2This definitely smoothens out the regions where different mips are drawn and actually was very effetive in hiding totaly any form of banding. I always wondered why this was not implemented in FS (either a Direct 3D limitation, or just a plain oversight of the issue/feature, or a technical limitation that made it impracticle to be implemented in FS compared to other games in 3D).

[LuisFelizTirado 33]

Good question, Jean-Luc, and also quite easy to check. In fact, I just did it this morning with the same Gib scenery.With LOD radius set to Small (2.5 quadrants), ground textures were blurry closer to aircraft, while with LOD radius set to Large (4.5 quadrants), they were sharper and clearer farther out. This was with custom textures, maximum resolution of 1.2 meters per pixel, and texture slider set to 1 meter.I would imagine that this is not valid for normal vector terrain since those bgls are all quad level 7, whereas photo bgls contain multiple LODs.http://forums.avsim.net/user_files/185171.gifBest regards.Luis