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LuisFelizTirado

FSX resolutions

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Would someone please explain to me the mesh and texture resolutions in FSX?Does 1 meter on the mesh resolution mean that there is elevation data for each square meter? If so, how is that affected by the mesh data (i.e.) if the data is 19 meter or 38 meter.On the texture resolution does 7 cm mean that each pixel represents 7 centimeters?

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Hi,Yes, those descriptions are correct. The mesh resolution is the distance between altitude point on the elevation grid and the texture resolution is the amount of meters (or centimeters) that is covered by one pixel of the image.I am not sure if FsX can really display 1 meter DEM data. If you data is only 19 or 38 meters it will not be able to display more than that of course. But in Fs2004 the maximum resolution is 19 meters.

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Thanks for the response, Arno. I have an airport that I worked on in FS2004 that I never got to look right. The runway has a berm at each end and a large land cut toward the center. Perhaps in FSX it can be properly modeled, assuming it is possible to replace just the dem around the airport.

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There are some very interesting new features in FS X terrain.Altitude mesh - the default mesh has multiple LODs included in each file, so there is no longer any need to create various mesh files with different LODs that appear closer or farther one gets. It is all in the same bgl. The default altitude mesh contains LODs 2-10, so the maximum default resolution for mesh is 38 meters.Ground textures - the default ground textures also have multiple resolution, in the form of mipmaps, I suppose. The maximum resolution for the default textures is 1 meter per pixel. However, it is possible to create ground tiles with resolution up to 7 centimeters per pixel - this can take a long time to compile and create very enormous files. In the absence of such terrain, however, it is useless to set the slider to greater than 1 meter.All Resample output - all files created with Resample (land and water class, altitude mesh, photoreal ground) are no longer constrained by LOD boundaries. In the past, these files were clipped to a LOD - no longer. It is now possible to set Destination bounds for them that can fit as tightly around the desired data as one wishes, without bothering about any particular grid.Best regards.Luis

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Very interesting, Luis!I'm really looking foward to the FSX SDKs!

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Hi all,something to keep in mind about both mesh resolution (and, to some extent, texture res too) is that the *displayed* resolution is independent of the resolution of the input data.The sim "doesn't care" what resolution your source data are; it will always up- or downsample to the parameter settings given to it in the cfg files and display menu. That's why it may very well make sense to max out the terrain or texture resolution settings in FSX. For example, a higher resolution setting may improve on the display of slopes and cliffs, even with mid- or low-res mesh (I know this to be a fact with the odd new water-turns-to-rock-on slopes "feature" in FSX). Similarly, a high setting for textures will allow the road vectors to show their full detail, which, according to ACES, is higher than 1m.Having said that, we haven't had a chance yet to test the effects on visual display and resource use with these sliders. For example, has the display distance of the mesh "rings" (i.e., automatic switching to lower LODS at specific distances from the user) changed at all? Does a high setting for mesh resolution lead to terrain morphing or ground shawdow issues as a TMVL=21 setting does in FS9? Etc.Cheers, Holger

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Hi ther Holger I will look into the above to-morrow after I get back from work. Dan Martin

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>something to keep in mind about both mesh resolution (and, to>some extent, texture res too) is that the *displayed*>resolution is independent of the resolution of the input>data.>>The sim "doesn't care" what resolution your source data are;>it will always up- or downsample to the parameter settings>given to it in the cfg files and display menu. >Holgar:If I understand your post correctly, are you saying that the "display resolution" settings interpolate the "data resolution"?I.E. If you have display resolution at 1 meter, and your data is at 19 meter...the simulator "inserts" values in between data points?Sorry to be so dense, just having trouble understanding how it really works.

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Hi there,That's actually a nice way of putting it: "display resolution settings interpolate the data resolution" and that's essentially how it works. Obviously, you won't get more accuracy by interpolating a 19-m mesh at 1 meter res because the interpolation is linear or something similar. Thus, oversampling may seem useless. However, my point was that other aspects of the terrain engine, in particular the interaction of various landscape elements, may benefit from using a higher resolution setting. Whether this is the case and what the negative side effects are, if any, will have to be tested in detail.Cheers, Holger

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This is an extremely interesting feature of the new terrain engine and one worth investigating. What is the intrinsic value of on-the-fly interpolation? Does it serve to "equalize" the altitude mesh, as it were, and to provide the same level of detail no matter what the terrain? Are there any other advantages, or unwanted consequences?Using the island of Saba as a test-bed, small, easy to visualize, I made 2 simple mesh files (from SRTM version 2 data) containing only one LOD level each - LOD 7 and LOD 8 - and placed the terrain setting so as to view at the native resolution, and then as interpolated by FS.First, however, and as a basis for comparison, here is the default mesh containing LODs 2-10 and with the terrain setting at 38 meters (LOD10):http://forums.avsim.net/user_files/158453.jpgThere is no interpolation and FS simply loads and displays the data, I assume (although it is anybody's guess as to how the terrain engine works, since the FS Team does not reveal the inner workings of the game.)Now, the LOD 7 mesh with terrain set to 305 meters (LOD 7):http://forums.avsim.net/user_files/158454.jpgWhen terrain is set to 38 meters, and the terrain engine has to interpolate, here is the result:http://forums.avsim.net/user_files/158455.jpgThere is a visible difference, but not much. However, this is not surprising, since there was not much information there to start with, so not much interpolation can be done.And, anyway, it is not as if there is anyone making LOD 7 mesh that would need to be interpolated to a higher resolution. Generally, I assume that the lowest resolution source data found for the world is the SRTM stuff. Normally, at around 90 meters resolution, this should be compiled to LOD 8 (152 meters), but nobody does this. At the cost of less accuracy, most SRTM is compiled to LOD 9 (76 meters), and therefore is already interpolated.Nonetheless, it was interesting to see a LOD 8 mesh in this example, so here it is with terrain set to 152 meters:http://forums.avsim.net/user_files/158456.jpgWhen terrain is set to 38 meters, there is some visible interpolation:http://forums.avsim.net/user_files/158457.jpgThere is very little difference when terrain is set 19 meters:http://forums.avsim.net/user_files/158458.jpgIt is interesting to compare the default mesh and this LOD 8 mesh, with terrain set to 38 meters:http://forums.avsim.net/user_files/158459.gifTwo things here: - There is a noticeable shift. I doubt if this is due to the on-the-fly interpolation. Rather, I had noticed that the default FS X mesh for the Caribbean has rather dirty water, reminiscent of the first version of SRTM data. I cannot imagine where else this data could have come from, so I assume that SRTM version 1 is the ultimate source. And I had already noticed this shift in the data when the SRTM version 2 came out a year ago. So, I would just put it down to that - a basic difference between SRTM versions 1 and 2. - Aside from the shift, there are evidently differences in the mesh. This is clear - the very shape of the terrain is different. This is to be expected, and undoubtedly unavoidable. Probably nobody would notice it except somebody who lives there, so it is perhaps not very important. And after all, we are looking for realism, and not absolute accuracy.So, all in all, it seems that this interpolation feature is quite welcome and not particular harmful.Commercial vendors are set to release 19-meter terrain on the FS community in the days to come. So, their clients will need to set terrain to that resolution in order to display the new mesh. And if they fly outside of the coverage of those files, then FS will simply interpolate the default terrain to the same level, with only slight inaccuracies in the ground.On the other hand, we could suspect that greater resolution terrain will affect performance, and that 19-meter terrain whether present in the mesh bgl or interpolated, is going to be noticed in the frame rate counter. Although, this needs to be verified and extensively checked.If FS were providing great levels of performance, all of this would probably not be very important. It remains to be seen how precisely this type of higher resolution will impact on already difficult FS X performance. And whether on-the-fly interpolation will make matters worse.Best regards.Luis

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