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boez

Terrain LOD slider - FSX v P3D

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I have read a couple of times that the slider in P3D which controls the LOD of the terrain rings around the aircraft is set to 6.5 when at its maximum. Also it would appear that the tweak which allowed you to increase that value in FSX.CFG no longer works in P3D, for example setting LOD_RADIUS=8.5 does not work. Using the false colour mip-map texture files that I used to experiment with that tweak last year I decided to repeat the tests in P3D. As in previous post inner ring = white = 1024x1024 (i.e. sharp detail), Outter ring = deep red = 64x64 resolution mipmap (i.e. less sharp). See http://forum.avsim.net/topic/423417-lod-radius15-but-its-not-about-distance/

 

I can confirm that the tweak no longer works in P3D and that the LOD rings are a combination of the inner rings being 5.5 LOD and the outer rings being 6.5 - please see attached images.

 

Plockton on the west coast of Scotland is my chosen airport - image 1 with standard texture files, image 2 & 3 is FSX using the false colour mip-maps texture with LOD at 5.5 and 6.5 respectively. Then image 4 is P3D with the terrain LOD slider set at maximum (approximately 6.5 LOD). Its quite difficult to compare them statically so I've added some animated gifs which compare the important images. As you may be able to see the inner rings of P3D match FSX when FSX is set at 5.5, while the outter rings of P3D match FSX when FSX is set at 6.5. Not sure why LM decided to do it this way but it explains the more blurred appearance of textures closer to the aircraft in P3D compared to a similar configured FSX setup (i.e. set to 6.5).

 

HTH

Andy

 

 

Image 1 - Plockton

fsx_plo.gif

 

Image 2 - FSX - LOD = 5.5

FSX_5.5.gif

 

 

Image 3 - FSX - LOD = 6.5

fsx_6.5.gif

 

 

Image 4 - P3D - LOD = 6.5

p3d_max.gif

 

 

Image 5 - Plockton default v rings

ci92d.gif

 

 

Image 6 - FSX (LOD = 5.5) v P3D

chtyc.gif

 

 

Image 7 - FSX (LOD = 6.5) v P3D

chtwo.gif

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Thank you for this, very interesting findings. I guess this is why people with photoscenery complained that LOD=6.5 wasn't enough. If Lockheed Martin aren't going to remove the 6.5 cap, I hope that they will introduce true 6.5 at least.

 

I'm also wondering, why does mesh seem a lot more crisp and defined in the FSX screenshots?

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The lower LOD is generally under the aircraft and not visible to the pilot in VC mode. LM did the same thing with autogen.

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This used to bother me, but since installing the latest NVidia driver textures at a distance seem to have sharpened a little bit.  Not sure if it is some other setting, I did change a few, or if it is placebo, but I'm no longer irritated by it.

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I'm also wondering, why does mesh seem a lot more crisp and defined in the FSX screenshots?

Simple answer really - I neglected to make sure I'd set the time the same in P3D and FSX! Caused me to wonder initially when I was preparing the post but the lower sun caused darker shadows.

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Simple answer really - I neglected to make sure I'd set the time the same in P3D and FSX! Caused me to wonder initially when I was preparing the post but the lower sun caused darker shadows.

 

OK, thanks!

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The lower LOD is generally under the aircraft and not visible to the pilot in VC mode. LM did the same thing with autogen.

 

True unless you're a slow and low pilot or like hilly/mountainous areas!

 

Plenty of the high resolution mips (white, red and magenta) still visible at 2,000ft: (note conversion to gif has caused poor image quality - must use jpg from now on!)

 

2000.gif

 

Not so many at 10,000ft:

 

10000.gif

 

 

I guess as in most things a compromise can help but if this was done to save memory usage then the saving was surely negligible?

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I've posted about this a few times before (information is from Beau H.).  The P3D LOD radius is a limitation of DX11 Tessellation texture array size (2048 bytes as I recall).  There is no "simple" option to just exceed this limit ... the cap is not an artificial one, it's a real one based on texture array size.

 

Possible ways around this limit:

 

1.  Code changes on how the terrain processing works based on Tessellation On/Off 

-- Two distinct terrain engines, very difficult to maintain

 

2.  Code changes to allow for multiple tessellation texture arrays as to allow higher LOD radius

-- Major changes to terrain processing with very high potential of breaking compatibility

 

I would guess these types of changes would best be aimed at a future major product version i.e. 3.x (be it 64bit or whatever LM decide).

 

Cheers, Rob.

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Prepar3d.cfg

 

For Trees you can do this, but I'm not sure about Buildings.

 

AUTOGEN_TREE_MAX_DRAW_DISTANCE=9500.000000
AUTOGEN_TREE_MIN_DISTANCE_TO_LOD=2500.000000
 
change to
 
AUTOGEN_TREE_MAX_DRAW_DISTANCE=12000.000000
AUTOGEN_TREE_MIN_DISTANCE_TO_LOD=12000.000000

 

Obviously this will impact frame rates and increase VAS usage ... you've been warned.

 

Cheers, Rob.

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Note, those changes also affects ORBX street and road lights, which are modeled as "trees".

 

Hey Andy, good work on this as always.

 

Not so many at 10,000ft:

 

That's true, but considering that a) one is most likely flying a whole lot faster at high altitude and b ) a pilot really doesn't need to see lot of ground-based detail when up that high, I don't see this as a major problem.

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That's true, but considering that a) one is most likely flying a whole lot faster at high altitude and b ) a pilot really doesn't need to see lot of ground-based detail when up that high, I don't see this as a major problem.

Totally agree :) As I said in my post a simulator has to make compromises.

 

 

 

In fact this was never meant to be a P3D bashing thread simply a comparison between the two simulators and their differing approach based on measurements (rather than the usual assumptions) to assist me in deciding whether it's time to move to P3D.

 

I run FSX at LOD = 8.5 (with zero OOM mainly thanks to Win7x64 + DX10 + GA aircraft) and so the LOD of 6.5 that P3D is limited at is jarring but the improved lighting/weather representation/AG may persuade me to put up with that. Well maybe ;)

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