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FSX Higher LOD terrain not drawn.

benclark

benclark

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Well I just made a LOD12 (9.5m) terrain mesh of Mount Saint Helens using the 10m source data from 3DEP and when I put it in the sim I saw it and thought great it worked (been a VERY long time since I've done any mesh work) so I turned off the Addon Scenery folder to see the difference between it and default and was faced with what appeared to be even higher resolution mesh. Checking the BGL files with TMFViewer indeed the default is LOD14 (2m) mesh which has raised an interesting question for me now.

I believed that yes addon files should always be above the default with mesh first and airports above but that if a file below had a higher resolution it would be drawn preferentially, is this not the case? Are all of us with addon mesh missing out on this significantly higher resolution mesh without realising it?
 
Hello:

Indeed, Mount St. Helens was used as an example for the FSX SDK Resample FractionBits parameter:


https://msdn.microsoft.com/en-us/library/cc707102.aspx#UsingScaledElevationValues

http://blogs.msdn.com/b/ptaylor/arc...esign-design-goals-and-design-influences.aspx

http://www.avsim.com/topic/395348-fsx-default-terrain-vs-downloads/page-2#entry2556667


FYI: FSX Terrain mesh BGLs are displayed by the FS rendering engine based on their internal LOD resolution specified when created via FSX SDK Resample ...and not based on their relative position in the FS Scenery Library GUI stack of Area layers (which otherwise confers a 'virtual "priority" number' for most- but not all- other types of 'non-mesh' FS terrain scenery BGLs*).

Whenever a "active" Terrain mesh BGL (whether default or 3rd party) has a internal resolution higher than the settings 'enabled' by the FS GUI terrain mesh resolution slider (or the manually edited FSX.Cfg file terrain resolution setting), that terrain mesh data will be used preferentially over the ACES default terrain mesh.

Whenever a "active" Terrain mesh BGL (whether default or 3rd party) has a internal resolution lower than the settings 'enabled' by the FS GUI terrain mesh resolution slider (or the manually edited FSX.Cfg file terrain resolution setting), the ACES default terrain mesh data will be used preferentially over the 3rd party terrain mesh.

However, in both the above scenarios, the FS rendering engine will interpolate (read: up-sample or down-sample) using the highest resolution data of all supplied "active" terrain mesh BGL sources ...to tessellate and draw the terrain surface according to the settings 'enabled' by the FS GUI terrain mesh resolution slider (or the manually edited FSX.Cfg file terrain resolution setting).

Hope this helps ! :)

GaryGB


[EDITED]

(*) Regarding file loading priority and/or 'virtual "priority" number' for most- but not all- other types of 'non-mesh' FS terrain scenery BGLs*)...

http://www.blog.scruffyduck.org.uk/index.php?/archives/99-Priority-Matters.html

https://www.google.com/#q=site:www.fsdeveloper.com+VTP+layer+number

[END_EDIT]
 
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Well then I've found a bug of some kind then, I had the mesh slider at it's highest setting (1m) and when my BGL file was in place it was still being drawn preferentially over the higher resolution default terrain. Not sure why it would be doing this.
 
benclark said:
Well then I've found a bug of some kind then, I had the mesh slider at it's highest setting (1m) and when my BGL file was in place it was still being drawn preferentially over the higher resolution default terrain. Not sure why it would be doing this.
Click to expand...

Hi Ben:

Reportedly, most of the FSX default terrain mesh BGLs were created from 30 meter source data.

Possibly your custom 3rd party terrain mesh BGL alpha-numeric file name may have forced the load priority ? :scratchch

(see scruffyduck's "Priority Matters" tutorial linked via the edit to my post above).

GaryGB
 
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Hi Ben:

I failed to mention above, another "gotcha" (I'm not so sure it is a 'bug') in the way that the FSX rendering engine works when rendering a local ground surface with Geographic coverage by more than one terrain mesh BGL, when each of those BGLs also contains differing LOD extents; this scenario might possibly explain what you reported above. :idea:

benclark said:
http://www.fsdeveloper.com/forum/threads/higher-lod-terrain-not-drawn.435658/#post-727362

Well then I've found a bug of some kind then, I had the mesh slider at it's highest setting (1m) and when my BGL file was in place it was still being drawn preferentially over the higher resolution default terrain. Not sure why it would be doing this.
Click to expand...


For example:

*1 BGL has more high resolution LODs and a smaller Geographic coverage area than the other (ex: your custom terrain mesh)

*1 BGL has more low resolution LODs and a larger Geographic coverage area than the other (ex: OrbX FTX PNW custom terrain mesh)


FS may persist in rendering only the lower LOD terrain mesh if you load and start a flight outside the Geographic coverage area of the BGL which has more high resolution LODs than the other (ex: your custom terrain mesh).

IIRC, Holger Sandmann was the first to report this initially baffling behavior by the FS rendering engine, wherein the larger Geographic coverage area of an existing lower LOD terrain mesh BGL displays with top priority, and the higher resolution LODs of the custom terrain mesh BGL are not displayed when one loads a flight session outside-, then flys into- ...that smaller Geographic coverage area of higher resolution LODs.

[EDITED]

Reportedly, in such a scenario of "over-lapping LOD extents" terrain mesh BGL coverage, one may be able to display that higher resolution LOD terrain mesh only when one loads a new flight session inside that smaller Geographic coverage area of higher resolution LODs.


I will try to find and link to a few more threads specific to this "terrain quirk" of the FS rendering engine, but here is some related info on manually specifying the range of output LODs in one's FS SDK Resample INI file:

http://www.fsdeveloper.com/forum/th...ticle-create-mesh-using-global-mapper.433307/


UPDATE:

A few links for those interested in reviewing some additional info related to this type of display priority scenario: :coffee:

http://www.fsdeveloper.com/forum/threads/lods-for-high-resolution-photoreal.436785/#post-738368

http://www.fsdeveloper.com/forum/threads/photoscenery-texture-problem.436547/#post-735983

http://www.fsdeveloper.com/forum/threads/higher-lod-terrain-not-drawn.435658/#post-727464

http://www.fsdeveloper.com/forum/threads/lods-for-hi-res-photoreal.435132/

http://www.fsdeveloper.com/forum/threads/fsx-photoreal-naming-conventions.20989/


FYI: The general idea is that to ensure a custom terrain mesh BGL displays with top priority above either the default or another 3rd party terrain mesh BGL, one must specify that FS SDK Resample outputs the same low LODs (or even 1-additional LOD 'lower') into that custom terrain mesh BGL ...as are contained in any other "active" terrain mesh BGL which has the same local Geographic coverage area. :pushpin:

[END_EDIT]

Hope this helps with your project ! :)

GaryGB
 
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That would explain it exactly, I was starting away from the Mount and then moving in to the area. This is interesting as I compile my BGL's from LOD 5 upwards as I believe that's the default coverage. Will be looking in to this more, gotta love the sim as it's always teaching you lol
 
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