Terrain Mesh Resolution

[DAL1850 51]

Does anyone happen to know what the resolution of the stock elevation data used in P3D is? 10m? 19m?

[GHarrall 494]

I assume it's the same as fsx which for USA I believe was 38m and the rest of the world 156m

 

Edit

 

USA 38m

Canada, Europe, Mexico 76m

 

Rest of world varies from 156m to 306m

 

I may be off though......

[DAL1850 51]

Trying to decide if I should drop my FSG DEMs in or not. The other consideration is whether or not high res DEM data is even necessary anymore with real time tessellation built in.

 

Off the cuff, the resolution of the terrain mesh looks markedly better than FSX does out of the box (hence the question).

[mganz121 159]

Off the cuff, the resolution of the terrain mesh looks markedly better than FSX does out of the box (hence the question).

Yes it does and I suspect that may (?) be due to the better graphics and smoother experience.

 

The frame chasers still have to work this out though.

 

Sent from my GT-N7100 using Tapatalk

 

 

[GHarrall 494]

The tesselation can only work with the base data that is there. If anything increased resolution elevation data should make things better than ever. You should be able to see the higher resolution dem out further than ever possible previously

[DAL1850 51]

One of my biggest complaints with FSX and my universe of 10m DEMs + photoscenery are the terrain load times. So I'm weighing the visual quality of a using higher resolution DEMs vs performance. If dynamic tesselation is strong enough to smooth those hard low-resolution edges you see in FSX, I'd be willing to to take that in exchange for speedy load times.

 

I'll drop a couple of BGLs in and take some before/after shots to compare to see how things measure up.

 

EDIT - Another point to consider. Why is the default terrain mesh resolution 19m if the provided DEM is only 38m?

[DAL1850 51]

No doubt about it. The mesh in P3D (at least in the States) is sampled at 19m (LOD11). This makes sense, given the default has been set to 19. Moreover, the visual differences between FSG 9.8m(LOD12) mesh and what you see in P3D out of the box w/ tessellation enabled is next to negligible. I can't make a compelling argument for using a third party mesh unless you were flying over an irregular grid of stalagmites or enjoy long load times. Justin(FSG) can be none too pleased with that development.

[Jimmy RFR 406]

Perhaps for the lower 48, it may include acceptable mesh, but for the rest of the world it would appear that the same mesh that was in FSX is still in use. Fo example, I took a flight earlier out of PAKT; there's a huge cliff in a bay just north of the airport that exists in default FSX - it also exists in default P3D as well. I do plan on making the install of some mesh a priority.

[MikeT707 1,181]

No doubt about it. The mesh in P3D (at least in the States) is sampled at 19m (LOD11). This makes sense, given the default has been set to 19. Moreover, the visual differences between FSG 9.8m(LOD12) mesh and what you see in P3D out of the box w/ tessellation enabled is next to negligible. I can't make a compelling argument for using a third party mesh unless you were flying over an irregular grid of stalagmites or enjoy long load times. Justin(FSG) can be none too pleased with that development.

Jason,

What is the tessellation supposed to do in P3D2?

[DAL1850 51]

Perhaps for the lower 48, it may include acceptable mesh, but for the rest of the world it would appear that the same mesh that was in FSX is still in use. Fo example, I took a flight earlier out of PAKT; there's a huge cliff in a bay just north of the airport that exists in default FSX - it also exists in default P3D as well. I do plan on making the install of some mesh a priority.

 

Makes sense, considering LM is a US defense contractor. They may not have invested in elevation data beyond the lower 48. Maybe there's hope for Justin yet

 

Jason,

What is the tessellation supposed to do in P3D2?

 

Tessellation is a mathematical/graphics term that refers to subdividing a low-resolution surface of a model (low vertex, low poly count) into a high resolution one by subdividing larger polygons into smaller ones - giving the appearance of greater detail to the viewer. In this past, doing this in real time was not practical because it is computationally expensive. Instead, game developers relied (and still do) on something called geometry LOD (level of detail) by baking the tessellated geometry into the game assets. 3D models typically ship with high-polygon versions (for viewing up close), a variety of mid-range ones, and a low-poly/res version (for viewing far away). The graphics engine will typically select the appropriate model based on how far away the object was from the virtual camera. Fewer polygons = better performance. Fewer polygons = blocky unappealing objects too. So you can see the need to strike a proper performance/quality balance based on viewing distance.

 

"Baking" LODs is harder to do with a terrain mesh because it isn't "an object" in the classical sense. It's a procedurally generated geometric surface (the code generates it from raw data files in the scenery BGLs) that requires dynamic tessellation/subdivision of the terrain grid "on the fly" as you move over it. This is why you can see the terrain nearest the aircraft morph from looking flat, smooth, and blocky to looking sharp, bumpy, and detailed (good texturing also helps with that illusion too). In DirectX 11 this kind of dynamic geometry computation can be done in real-time by the uber fast GPU workhorses...and they are far more efficient at it. Even moreso, the CPU doesn't have to copy the data back and forth geometry updates from the computer to the video card - the GPU can just do it right there as it's rendering the scene to your display.

 

Anyway, P3D supports DirectX 11 and if your video card can hack it (most newer cards do), it can result in better looking terrain for less cost. It effectively allows a greater degree of terrain detail to be present in-game (the GPU is creating it) than what the raw data would normally present as if rendered without. P3D uses dynamic tessellation in the terrain system. I'm not sure if they're using it anywhere else. Apart from the aircraft, most of the scenery models in the game are very simplistic and low-poly to begin with.

 

That said, some of the older cards which claim DirectX 11 compliant aren't - or they do a ###### poor job of it (worse than the CPU). My old Radeon 6900-series had hardware support for tessellation, but enabling it drove P3D performance straight into the toilet. I was really alarmed when I started P3D for the first time - with its "modest" default settings - and discovered I had gone from 30 fps in FSX to 6 in P3D. Disabling GPU tessellation (which is on by default) on the graphics card was actually a boon in this case. So people with older mid-range cards (2 or 3 years old) may try disabling GPU tessellation and find life is a whole lot better.

 

(sometimes a picture paints a thousand words)

 

[meshman 109]

No doubt about it. The mesh in P3D (at least in the States) is sampled at 19m (LOD11). 

 

Justin(FSG) can be none too pleased with that development.

 

Strange... When I look at the files in TMFviewer it reads LOD10 or 38m. Looked at 0303 (Hawaii), 0202 (Texas) and 0102 (N.Kalifornia). I believe if you do a file size check with FSX you will see little, if any difference? I haven't done a scan of all the files yet, but I will! :lol:

 

 

And you need to get current on FSGenesis. It's now owned by FS Pilot Shop...

[Jimmy RFR 406]

So then here's a question for you mesh experts (and I mean that very sincerely):

 

If the current mesh that we're using has LOD's baked into it, is there an advantage to using high levels of tessellation at all? It would seem to me that our current mesh is 'optimized' for the older FSX method of displaying mesh.

 

Conversely, if tesselation is indeed making 38m mesh appear to be as good as 10m mesh, does that mean that with tessellation, our 10m mesh will seem to be even more detailed than what it was??

[MikeT707 1,181]

 

 

"Baking" LODs is harder to do with a terrain mesh because it isn't "an object" in the classical sense. It's a procedurally generated geometric surface (the code generates it from raw data files in the scenery BGLs) that requires dynamic tessellation/subdivision of the terrain grid "on the fly" as you move over it. This is why you can see the terrain nearest the aircraft morph from looking flat, smooth, and blocky to looking sharp, bumpy, and detailed (good texturing also helps with that illusion too). In DirectX 11 this kind of dynamic geometry computation can be done in real-time by the uber fast GPU workhorses...and they are far more efficient at it. Even moreso, the CPU doesn't have to copy the data back and forth geometry updates from the computer to the video card - the GPU can just do it right there as it's rendering the scene to your display.

 

I do not have P3D yet (my new build is coming soon) but am wondering if you are seeing tessellation in the sim in the form of displacement mapping.  From my understanding, this would change the rendering of smooth ground to be more bumpy and uneven.

[DAL1850 51]

Strange... When I look at the files in TMFviewer it reads LOD10 or 38m.

 

I suspect what they're doing is using the tessellation to interpolate 38m down(up?) to 19m - that or the UI is lying . The "P3D" 19m isn't identical to the "FSG" mesh, but it was pretty damn close in the couple mountainous places I looked. If it is upsampling from 38m, it's only doing it for 1 LOD. I noticed no differences in the terrain geometry going lower than 19m (but maybe the deltas were too small for me to notice). I also noticed little benefit from changing the Tessellation Quality from High to Ultra - it made a couple little bumps and depressions appear here and there, but nothing to write home about.

 

I'm thinking perhaps the terrain mesh slider really means "Tessellated to look like XXm".

 

 

So then here's a question for you mesh experts (and I mean that very sincerely):

 

If the current mesh that we're using has LOD's baked into it, is there an advantage to using high levels of tessellation at all? It would seem to me that our current mesh is 'optimized' for the older FSX method of displaying mesh.

 

Conversely, if tesselation is indeed making 38m mesh appear to be as good as 10m mesh, does that mean that with tessellation, our 10m mesh will seem to be even more detailed than what it was??

 

Good question. And I don't know (probably because I'm not a mesh expert lol). Off the cuff, I would think the benefit would be "less" but there is still some benefit to having the geometry manipulated directly in VRAM as opposed to having the CPU pull the geometry from system RAM and shuttling it over to the bus to the video card.

 

To your last question: again without seeing it, it's hard to say...but I think there is a point of diminishing returns. The GPU's are designed only to tessellate a scene so much (configurable through the driver)...so if your source mesh is high res to begin with, I wouldn't expect it to be another order of magnitude better. Kinda the point of GPU tessellation is to allow "lesser/lighter poly" geometries to be presented to the graphics card and become "rezzed" in dynamically at draw time.

I do not have P3D yet (my new build is coming soon) but am wondering if you are seeing tessellation in the sim in the form of displacement mapping.  From my understanding, this would change the rendering of smooth ground to be more bumpy and uneven.

 

I haven't seen this, but then I haven't been looking for it either. I don't think - given a perfectly flat area of terrain polygons you're going to get pseduo-generated displacements to simulate uneven terrain. Where you tend to see it is in areas of existing elevation or depression - the gradients are accentuated where they would ordinarily appear "soft" and undefined...they appear smoothed where the geometry would normally present a hard edge.

[astroavion 2]

I've been using computers since about 1980, and you guys make me feel like a complete idiot. lol

 

How and where did you guys learn all of this stuff?