FSX, Crysis and framerates

[WarpD 824]

>>1) FSX is generating terrain real time. If you think>>otherwise, then you don't grok what the statement actually>>means.>>I have no idea what you mean here. If it's "generating" the>terrain in real time, why do I have 20+GB of terrain BGLs,>textures, models etc in my FSX folder?>>When you say Crysis is "prerendered" I don't know what you>mean either - if it was prerendered you wouldn't even need a>good video card because it would just be playing back a video>or something to that effect.>>Both games *render* in real time - they do not create their>"maps" in real time.Generating terrain in real time means that all of the trees/buildings and other such items on the landscape are 'created' dynamically. ACES calls it autogen. Not a bit of Crysis is dynamic because absolutely every single item on the landscape is precoded in place. Right down to the individual tree/pole/wall/building/shrub.Imagine having to do that for a world, literally.

[Guest JeanLuc_]

Can we suppose every grass blade on the ground in Crysis is also hand placed? I thought it was generated at runtime?!! I would have bet... Sure enough, their grass floats with wind, and folliage on trees support full real time collision and interaction with the world (bullets, actors, wind).The only difference I see in both engines, and pardon me for drawing conclusions too early (I just read the published documents, I've toured myself in the inner working of FS to draw these early conclusions):1) FSX render engine, tesselates in real time the mesh based on many factor, one important is the distance to the viewer, and the level of detail locality (i.e. abrupt changes in elevation in close distance leads to high poly count, small changes over large distances leads to low poly count). No different that any game, some using pre-computed meshes, but overall, not an heavy process since it can be span among a long time frame (i.e. you compute the lod 100km away, and it takes the user 10 mins to reach this location).2) FSX builds tiles (the texutres) in compositing images (the individual land class textures) using vector/binary data (shapes and density maps). It blends it with mask maps, and overlay higher level elements (rivers, roads etc...). It uses antigrain for this (or similar gfx composition code). THIS is to me the factor that makes the engine slow. It requires for each cell, to compute the gfx blend, and then to upload the texture to the video card. No 2 tiles are the same, and this leads to high cache miss in the CPU (during composition) and bad performance with the video card (efficient at reusing textures).3) Crysis, like most "regular" games, seems to have a pre-set of textures.4) shadow maps are computed with FSX, somewhat at runtime (but not real time, like updated every 5 minutes). It does not cope well with high level of detail (i.e. it uses a lot of computations/polys to make the shadows of moving objects), and for ground shadows (terrain mountain shadows), it "paints" the shadow on the tiles.5) Crysis shodows are real-time (each grass blade seems to cast shadows in realtime as they move with wind). I suspect an efficient useage of shaders.6) FSX is new at using shaders, FS9 started to use few.7) FPS games used to use shaders, and improve on technology, since shaders became available. Most of the shaders techniques documented at NVidia, ATI or dev books, are from major FPS game developpers as far as I've seen.8) I suspect 80% of the development effort to code FS is in missions, content, graphics (tiles), back compat, third party integration, and 20% on the actual 3D engine9) I suspect 80% of the development effort to code a FPS shooter is in 3D engine.these are just few of my assumptions, nothing more.

[Guest]

The FSX engine is extremely inefficient in what it does. I will give one simple example:Set your plane in a corner or the airport and turn off autogen. Load the sim and view the frame rates. Now change autogen to max. Frame rates will halve or worse. Even though all the AI are not even visible, this engine is still rendering them. [edit]

[dmaher 0]

edit...on second thought I'll stay out of the conversation. respect...

[Guest]

If you can not see objects, the 3D engine should not render them! its that simple. It's just one of the reasons its not scalable!

[Tabs 2,790]

Wingnut,Can we try to be civil here while having this discussion/debate? The ACES guys aren't stupid and I'm sure they know the engine related reasons for FSX's lower than average performance at high detail. No need to take such an aggressive tone IMO.Phil,Ok thanks for correcting me. Am I correct though in saying that the models for the autogen etc are in fact premade though - the sim isn't actually coming up with those shapes and stuff on the fly is it? That's what I mean here - I understand you're recalculating terrain and stuff on the fly... But stuff like airports, buildings, the AI planes, roads etc, that's all premade in the same way Crysis's trees and vehicles, AI enemies etc are correct?

[Guest]

ok "sorry"

[PhilTaylor 45]

I appreciate civil discourse, thanks.Some things are similar, some are different."Hi def" airports that have custom objects ( 1200 or so locations planetwide ) are similar in that there are pre-built objects that are loaded and placed. Same with the custom objects in cities. The scale of this, eg 1200 separate locations planetwide, might be a bit larger than the design points in Crysis have to deal with, but the idea is similar although let me clear again without vidding their source I am speculating there just like everyone else.Autogen trees and buildings are different. They are pieced together automagically from landclass mapping data and geographic/cultural region data on the fly. Thats why they are called Autogen. Trees use both landclass and geographic data to generate themselves. Buildings use geographic and cultural data as well as human footprint data to generate themselves. Autogen building roofs are actually stored in a separate bgl allowing even more dynamic runtime composition based on this cultural/regional mapping. That flexibility does come at a cost, though. But its hard to see how the user base would accept less variability in the world. Autogen gets its share of criticism for being too cookie-cutter as is. Its a hard problem. Cell densities and visibility have an impact here too. The range of Autogen is goes up to 6000 per cell for both buildings and trees. what is 2x6000x16=? 192k is what my math shows. That is just the Autogen objects for a 4x4 grid around the viewpoint. IIRC our grid is 2nm on a side. Thats only 8nm x 8nm. So our Autogen densities result in a lot of objects. But that is what it takes for LA, or London, or Paris, or Tokyo or any of the other big cities to appear real. Yes we batch, and yes we LOD - but even there its a lot of indivual objects even if you cut down the verts and use a single texture.The combination of the world object techniques is again somewhat unique. Usually its either fixed maps, or completely random maps. Not use of both specific fixed data at such a large scale with controlled variability to generate the illusion of planet Earth.The way the terrain textures are generated is pretty unique and that is how all vector data ( hydrology for streams, roads, rails ) coastlines etc appears. I highly recommend Adams' paper at http://dev.fsinsider.com/developers/Pages/GlobalTerrain.aspx. The overall terrain approach is noteworthy enough that GDC accepted a session proposal based on it in 2006.And the way night is handled is another difference. The lighting technique we use for night lighting allows generation of thousands of emmissive light sources which is how you get the wonderful nighttime city scapes. As well as the great night airport experience, which again is one of the reasons I begged to be able to fix the 737 and A321 because when they rolled by dark on the tarmac it really destroyed the night experience. If you dont know what I mean do this:1)take the Trike and roll along any major airport until you can view both the terminal, the takeoff runway, and the landing runway; 2)park it and find a good view, or slew if you can control it well enough, until you have a great vantage point3)turn the sim speed up to 4x, all AI works up until that pointThis gets you a great view of the airport night experience and its very soothing, almost like a screensaver and is something unique in FS in that we give you a pretty good 24 hr 365 day a year experience. AI is, I believe, the bit of the same and different. All AI follow paths. The scale of a continental road network is a bit different, though. And I think the nature of generating commercial flight plans within a connected network, relatively random but non-crashing GA flights, and several layers of boat traffic ( including commercial/military shipping and ferrys that follow timed schedules ) as well as the at-airport vehicle behaviors means both titles have non-trivial AI capabilities that have overlap and unique aspects.While all games do have commonality, genres do have differences. And those differences do matter in terms of design.

[Guest Lith1um]

Wow Phil, that was an interesting post. (yours, not the fsinsider link)

[Tabs 2,790]

Thanks for the info Phil - we all appreciate it?Do you know how the raw poly/triangle count differs between a typical FSX scene and something like Crysis or UT3?

[PhilTaylor 45]

Good question. I dont know enough to quote those numbers for the other titles.Another good metric to consider is unique materials since thats how you have to group objects for batching and instancing. Properties ( diffuse, specular, emissive ) + textures + shaders are all part of what a material is, so the each of those unique combinations defines a material "bucket" if you will and then the number of objects in each "bucket" is also an important number as that is a measure of the upper limits of batching efficiency.

[cat 2]

Just did that. Sydney Airport. No change framerates! Only+or-, one fps!!!Peter Sydney AustraliaFSX SP1 Vista GF 8800 GTS 4 gig ram 2 Core

[Guest JeanLuc_]

An update on Crysis, I've been told about this: you can run Crysis in Windows XP with what seems to be ALL supposedly DX10 only features, and it appears the game, in DX9, just rocks both in visuals and FPS.That is you get motion blur, HDR, advanced AI, advanced collision detection, dynamic moving objects, breakable objects etc...To me this just sums up the thread: as much it requires a large team of experts nowadays to build an Airliner addon for FS, it requires specialist in the 3D engine field to build a sound 3D engine, I just find this engine to rock for FPS shooters, and like many readers here, just wished it could also suit a flight simulator.http://www.crysis-online.com/forum/index.php?topic=11837.0Enjoy! I'm downloading the demo now!!

[Guest]

You can run it on all High settings and get " motion blur, HDR, advanced AI, advanced collision detection, dynamic moving objects, breakable objects etc..." under DX9. There are definately some differences under DX10 but I don't recall which ones. I know for sure DX10 allows for much higher physics (like breakable trees, destructible buildings) in multiplayer, which DX9 does not. I've been playing it, using the amazing Sandbox 2 editor and it's a great game. In the editor you can even create a tornado that will destroy buildings and you can watch the walls and roofs spin up in the air and get flung outwards. It really is pretty amazing stuff.

[Guest phenom]

It's so rewarding seeing your baby grow up.11 pages, and a celebrity appearance.*phenom wipes a tear.;-)