answered KFOT Rohnerville - High density grass option appears to eat VAS

[DAVIDF4]

KFOT Rohnerville - Unreasonably high VAS consumption when high density volumetric grass is enabled.

An observation (using FSX acceleration):
With the KFOT volumetric grass options turned completely off, I get memory usage of ~2500 MB (1500 MB remaining - this will obviously vary with aircraft used, etc). This is good. I also have KEKA installed and flying between the two airfields still leaves a decent amount of memory (there are points in the flight when memory usage actually drops).
However, when I turn the KFOT volumetric grass option to high density it appears to eat an extra 500K of memory.

Fly low swooping loops around the airfield and over the runway and watch the memory consumption climb. It tops off at ~500K more with the high density grass on.
This seems exorbitantly high for what you would imagine to be a minor detail in the grand scheme of things (just some repeated objects - grass and stones - and their display coordinates?). 
I would suggest then that there is a problem here and I think it's probably worth investigating, if for no other reason than to learn what is causing it and avoid whatever it is when developing future sceneries.

Normally I run with volumetric grass turned off at airports because it hurts my FPS (I've always been puzzled as to why the impact is quite as bad as it is). Here the FPS doesn't seem to be hit that much, but for me VAS is hammered. Fortunately this scenery still looks great without the extra grass so I'm not particularly traumatized by it  :-)

Can anyone with KFOT corroborate these findings?

[Alex Goff]

Hi David,

 

I did not play any role in development of KFOT, but in general grass and other vegetation can place an enormous strain on resources.

 

Vegetation is deceptive in how simple it looks, but it hits several things that can drain performance both in frames and memory. First is that it uses textures with alpha channels to render the transparency of the blades of grass, also there is usually some semi-transparent area at the base of the vegetation to blend it into the ground. Textures with alpha channels are both larger in texture size, and require more from the simulator to render them, determine which part of the texture is transparent, and then draw the texture with the proper sorting order so that objects do not end up behind other objects that have transparencies. 

 

Vegetation also requires a large number of polygons, to cover Block Island it took about 300,000 polygons for the grass alone. The ESP engine is good at eating up a lot of polygons with no struggle, but that does have its limits. More polygons equals more memory usage as well, especially if the models are individually placed instead of being all contained in one "master" model.

 

This is why we usually offer some control panel options to manage vegetation, they're a non-essential item for airports that has a disproportionate performance impact.

[DAVIDF4]

Thanks Alex,
And I obviously meant 500MB, and not 500K,
500MB is 1/8 of the total memory resources available, so that's why so much consumption for a 'minor' detail alarmed me.
I noticed that there was some discussion about KFOT VAS consumption way back, with some saying it was fine and others having issues.
It makes me think that perhaps it was the grass that was/is the problem for those people. So if nothing else, perhaps this thread might be useful to anyone experiencing VAS problems in this geographical area.
The KFOT - KEKA combination is perfectly viable if you kick the long grass into the, ermm, long grass. It makes for a very attractive looking area with good performance and with several other interesting airfields within a short distance as well.

[Jon Clarke]

Hopefully VAS will be thing of the past with P3Dv4 64 bit. Will you consider going for it and change from FSX, considering that your current FTX sceneries will work OK with the 64 bit option?

[DAVIDF4]

My FSX installation perfoms satisfactorily at the moment and I have it looking pretty nice. I also have a few FSX only licensed planes.
I'd love to not have to worry about VAS though.

 

As of right now a 64 bit version of P3D doesn't exist yet and I certainly won't be an early adopter (I'll let others beta test it), but once it proves stable and snag free, I'm sure I'll be moving up.
The fact that ORBX sceneries will continue to work on P3D is an important part of being able to make that decsion, as it means my investment is protected. I'm grateful for that, but on the other hand if this wasn't the case it would probably put a dead stop to my scenery buying at the current time. So it's a win/win situation for ORBX and it's customers in that respect.