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jimdbird

Mesh settings, and interpolation.

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If I have 76m mesh installed, but set the mesh resolution to 10m, does FSX use the 76m as is, or does it interpolate because of the 10m setting? Thanks,Jim

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Hi Jim:I have read that the resolution of the source data for the FSX default terrain mesh was 38.2 meters.Since FSX will load and run legacy format FS8/FS9 terrain mesh BGLs, it would be reasonable to expect that when running with those mesh BGLs available it might behave as pre-FSX versions of FS do when it comes to loading terrain mesh files: it might preferentially load and use the highest resolution mesh BGL it finds which covers the area in which the user aircraft is flying.However, since there is a new mesh BGL format now factored into the equation, one might wonder if because of the scalable design of the FSX mesh engine whether the FSX mesh might be given higher priority due to its potential to be scaled (via interpolation most likely) to render "empty resolution" datapoints when the slider is set at an 'artificial' higher resolution (less meters of distance between terrain elevation datapoint vertices) than was actually contained in the default mesh resolution/source data.In your scenario, the 76 meter mesh is technically lower than the default internal resolution of the FSX scalable mesh, and I would not normally expect it to be loaded.It is not impossible that there are some layering and/or naming tricks which work in FSX which we might wish to know more about to force a load of a particular legacy format and/or single LOD mesh file for a specific purpose; I'm curious what FSX would allow us to do with that type of situation.Perhaps it is as simple as setting the default FSX mesh slider to a lesser resolution (lower LOD/QMID resolution=greater distance in meters between datapoints/vertices in the rendered terrain mesh!).Thus, it might be possible to force display of your 76 meter 3rd party mesh by setting the FSX mesh slider at a number greater than 76 meters (ex.: 152 meters) enabling that 76 meter mesh BGL to display instead of the default FSX mesh BGL.Holger has previously commented on related issues, and it would be interesting to know more about how legacy mesh BGL files would be handled vs. default FSX mesh files with the prioritization process now that the multi-LOD type FSX terrain mesh BGL files are normally available at all times in a given flight even if we load an add-in legacy mesh BGL via the add-on scenery folder.Perhaps someone else has further insight on this process?http://forums.avsim.net/dcboard.php?az=sho...ing_type=searchGaryGB

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Hello Jim,FS X will interpolate both mesh and ground texture resolution. So, if you have a LOD 9 mesh (76 meters) and set the mesh slider to 10 meters, then FS X will attempt to add more resolution by adding elevation points.This is not worthwhile because: 1. interpolation affects performance. Resources are expended in the interpolation process that would have been used for other processes. The result can be blurry ground textures, lower frame rates, etc. 2. you will not get any visual benefit. I tested this last October - here is the island of Saba with a LOD 8 (152 meter) mesh and slider set to 152 meters:http://forums.avsim.net/user_files/175648.jpgThen, I set the slider to 38 meters, forcing FS X to interpolate:http://forums.avsim.net/user_files/175650.jpgThere are only minor differences and the general shape of the mesh has not changed at all. Understandable as the interpolation cannot create something out of nothing. And, performance will suffer from this.So, in general, there is no benefit to increasing mesh and ground texture resolution sliders beyond what is present in the scenery.Best regards.Luis

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Hi Jim:Interesting screenies and project... reminds me of the fun I once had in "4X4Evo2" climbing Pikes Peak!http://www.nvidia.com/object/game_evo2.htmlThe FS default and many Ultimate Terrain (UT) add-in/substitute roads are essentially mesh clinging VTP texture lines draped over the terrain mesh and default local land class textures.In the FS world (I would assume 'globally' with all such lines via the terrain.cfg file) such VTP lines have an option to clear autogen to an assigned distance on either side of the line, and also the option to have roads "indent" the scenery area beneath and to either side of the line. I don't believe the line can actually "flatten" (in the true sense of the word) the terrain mesh underneath the line just on the basis of legacy features available for VTP lines.I believe there is a feature available via SBuilderX and other tools, which in conjunction with the FSX SDK, would allow the use of assignable and variable per vertex elevations in LWM3 polygons, originally developed for use where mesh clinging water follows elevation changes in FS.I have not yet worked with LWM3 polys, but I believe there is a way to assign a land class texture other than water to an LWM3 poly (ex: a road texture) which would allow creation of flat roadway areas to implement corrections to FS terrain mesh rendering in problem areas to compensate for the way resample and/or the FS rendering engine seems to get biased by substantially different nearby elevations when rendering an area that should otherwise be flat according to the source DEM data used to create the terrain mesh itself. But where there are polygons, there are many data points to be dealt with by the FS rendering engine and increasing processing expense.Going to a higher LOD (smaller metric distance between mesh data points/vertices) might help as seen in your screenies, but as shown in your last screenie, at some point resample and/or the FS rendering engine still occasionally gets biased by a nearby set of data points for terrain and one literally encounters a 'bump in the road'.The possible drawback to the use of a very high LOD mesh in FSX to keep terrain mesh inconsistencies to a lesser level in roadway areas would be the high processing expense to the FSX real time rendering engine. Although UT-X has reportedly otherwise implemented many roads with traffic in FSX, apparently Pikes Peak has VTP-style roads in your screenies.I have not yet worked with the FSX SDK to create roads, but I am curious if there would not already be a way to create truly flattened roadways, so that the SimObject traffic works properly on top of continuous surfaces that change with terain mesh elevation. If not, I would suspect the same ongoing problem we thus far have had in FS with AI traffic at airports: there may not yet be an efficient way to move AI objects (SimObjects in this FSX scenario) over anything but completely "flat" surfaces.I am curious if there may also be a way in the FSX SDK to create a type of "roadway" (without traffic engine hooks, and different than the existing VTP textured road lines) in the form of a variable elevation "flatten line", rather than a LWM3 flatten poly (unless LWM3 polys can be 2 points and they can be placed sequentially along a vector path!).This road/line could be built from original source data containing both coordinates and elevation (an "X,Y,Z" data set) via the SHP2VEC routines and would be a smoothed subset of the terrain mesh slope data in the desired area of road placement. This could itself be textured with a road appearance, or placed 'transparently' on a layer under a VTP textured line (sort of like a land version of a water flatten).I would anticipate such a line might then be further subject to the terrain.cfg parameters for defined clearance of nearby autogen and optional 'indentation' of underlying terrain mesh when displayed by the FS rendering engine. I would expect that such a line would cause less of a hit on the FS rendering engine than a LWM3 poly, and depending on the terrain cfg parameters, it might be wide enough to satisfy the needs for the rural "roads" you are trying to smooth out. Perhaps someone else might comment on this possibility?PS: ATTN. Admins... Should this thread be moved to the Scenery Design Forum?Hope this helps! :-) GaryGB

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As I understand it, the 38.2 m resolution is in the lower 48 of the U.S. only. Elsewhere in North America and Europe it is 76 m, and you've got a grab bag of lower resolutions in the rest of the world. I'm quoting this from memory, so please correct me if I am inaccurate.Thomas[a href=http://www.flyingscool.com] http://www.flyingscool.com/images/Signature.jpg [/a]I like using VC's :-)N15802 KASH '73 Piper Cherokee Challenger 180

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Hey Gary,I think you are probably right about the mesh, and mesh resolution settings, having done about as much good as they can. As you stated they smooth in some areas, and generate bumps in others, as determined by the surrounding terrain.Although my computer skills are limited, I feel it may be

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Hi Jim:I had a moment to look at the FSX SDK document again; there is indeed an ability to render the vector roads without traffic, and with a choice of texture.I haven't spent that much time in FSX yet to know the answer to this, as I am busy finishing a project for FS9 right now.But, I guess one should just fly FSX to see if non-rural specially-textured multi-lane roads (with or without traffic) are flat with contiguous and aligned segments, and are properly (if at all!) rendered while descending slopes in the FS scenery.If not, one might wonder if my ideas for a special "flatten line" might still work.In FS9, the idea of using a very narrow width VTP line road "baseline" along with the "stream depth" set at -1 or -2 (which I believe also controls default and UT VTP lines, identified to FS I assume, by internal BGL layer number as "roads") with a superimposed wider generic VTP "road line" placed to drape over (at surrounding terrain AGL surface level but on different FS layer number) would be an interesting experiment to try.I suspect that Scott Gridley of the "FreeFlow" scenery projects would know something about this, and the possibility of creating and placing VTP lines and/or LWM3 polys in a sequential, batched, "extrusion" type of manner; it might be worth inquiring in his forum:http://www.fs-freeflow.com/forum2/index.phpArt Martin created many types of FS scenery components (and no doubt roads!) and innovated a sophisticated, batch function capable, 3rd party autogen annotation tool for his "Phoenix" scenery; he might have ideas on this too:http://www.simulatingart.com/mybb/index.phphttp://www.fsdeveloper.com/forum/forumdisplay.php?f=56I must address some other pressing FS9 scenery matters before I can tinker more on this intriguing set of possibilities, but I would be interested to read of any further discoveries you might make working with this; keep us posted will you?Hope this helps!:-) GaryGB

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Hi guys,there are indeed two types of terrain flattens in FS. Those associated with roads, railroads, and streams influence the mesh vertices individually, which explains the stepped result. In contrast, polygon-based flattens, which can be sloped, override the vertices to provide smooth surfaces. Thus, it is possible in principle to create smooth road surfaces by adding the latter types of flattens.I don't know why road/railroad/stream vectors use the former approach but I assume it has to do with performance. Also, working with sloped flattens quickly reveals that they have limitations too, e.g., at intersections of flattens. FSX seems a bit more forgiving in that regard.The equivalent for sloped road flattens are sloped river flattens. Allen Kriesman, creator of the Ultimate Terrain series, recently developed a new algorithm that computes accurate sloped flattens for rivers based on the surrounding terrain. It's mentioned in the UT USA FSX slide show pdf file on page 21 (Radial Elevation Theory): http://www.simforums.com/forums/forum_posts.asp?TID=21320 I assume that a similar approach could be used for roads though probably at an additional performance cost.Cheers, Holger

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Hi Holger:Very interesting ideas... thanks for the clarification and link! :-) GaryGB

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It will be interesting to see how Trainsim will handle this. Obviously, railroad tracks need a very smooth longitudinal path, so whatever solution MS come up with in their new TrainSim product may be transferable to roads.This would allow a whole new sim based on the FS architecture, that I'll call "Rally-Sim" for something better. Imagine a multiplayer car rally/race sim where you can drive around Colorado, or from Paris to Dakar....- regards, SkyDrift

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I'll bet before too much longer, a vision of computer simulation described a few years ago by Steve Greenwood (a notable authority on terain mesh technology for both Train Simulator and Flight Simulator), may become a "reality", as FS develops into a platform for 'virtual travel'. :-) Perhaps soon, we will be able to choose between "Planes, Trains and Automobiles" when we become "FS-Travelers"!:-coolGaryGB

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