Displacements is their terrain system. It actually works very similar to the sandbox tool in SketchUp.
You take a block, pick one face and convert it to a displacement. You tell it what power to split it into, then raise and lower the areas as needed. It isn't quite as flexible as the sandbox tool, but does work.
And yes, no where near as good as the terrain based systems like Crysis. But again each engine was designed for a different end-goal in mind.

You do have some impressive plug-ins. I am just barely learning programming, and I am trying to build a library of tools for working with sketchup and hammer. So far I have a modified massmaterial importer, and the two plugins mentioned above for fixing lines.

I think the most useful plug-in would be one that you can select a face, right click, and tell it how much you want to extrude it. The plug-in would first try to detect if it is a convex shape, if true, it would then group it and clean-up any stray or broken lines, then extrude it to the number entered. This would allow someone to simply break up a single face into lots of smaller pieces, and then extrude each one as needed.
Another good clean-up script would remove any textures from back-side faces, and if possible check if any backside faces are facing outwards. These two would solve 90% of the problems.

I am currently working on some tutorials an modified scripts to make this stuff easier on others.
However to use ANY 3D modeling program with ANY game, you need to read to documentation on both and learn both. I already knew a ton about SketchUp but nothing about hammer when I started. I constantly read tutorials and look at their developer wiki site. You can't just jump in and hope you did stuff right.
Right now I still spend a good amount of time correcting my own mistakes. But the tutorials will come soon. I have already modified the masstexture importing ruby script to properly name materials imported from L4D. Below are some tips I posted on the steam forums for working in SketchUp for export to hammer.

However answer to exporting VMFs is that SketchUp has two types of ways to group faces: Groups, and Components.
Groups are single-instances, you can make a copy of a group, but editing one group won't affect others.
Components are MUCH more powerful. Components are copies of each other, if you edit one component in a model ALL other components of the same name are also edited. Plus you can flip and mirror components. So for example in my buildings shown so far, most are symmetrical. I only have to model half the building. All the windows are components, so I only have to model one and the rest will follow.

When you export a VMF to Source it only looks for one type of object: A block or brush. A block of brush in Hammer is a convex object consisting of several faces.
See here on what is convex and what is concave:
http://developer.valvesoftware.com/wiki/Concave

The simplest type if convex object is a six-sided block. So in SketchUp that is a grouping or component consisting of six single faces.

There are four things that can break exporting a proper brush object:
1: Un-connected or broken lines. These are lines that either go nowhere, or don't meet at two other lines. There is ruby scipt here that can help to fix broken lines:
http://www.crai.archi.fr/RubyLibrary...roken_lines.rb
And one here that can help to remove lines that go nowhere:
http://www.smustard.com/script/StrayLines

2: Lines that split up a face. These can be hidden, or visible (Show hidden geometry reveals these) Erase these lines that split a single flat face in two.

3: Reversed faces. All faces in SketchUp have two sides, a front and back. You can use the Style editor to make the back faces show up as a different color. I choose magenta similar to the error texture in Hammer.
A VMF model can't have any reversed faces visible.

4: Textures on a reversed face. SketchUp allows you to apply textures to a reversed face. So even if you can't see them, you may have accidentally applied a texture to the back-side of a face. This can happen for example if a texture is applied to a face before extruding. The only good way to check for this is to remove a face and look inside the block. This can be time consuming, and caught me bad on one of my models. Tips: When extruding always extrude forwards to prevent this issue.

You can group multiple groups or components into larger and more complex groups and components. When you export these into hammer the groupings are preserved, you can un-group and re-group the items as needed in hammer.

As mentioned before, there isn't any UV mapping when exporting VMF models. All textures get reset to standard scaling upon export. So cleanup is often needed in Hammer. I have sent valve feedback on this, there is also a e-mail address on the wiki if you want to send your own feedback.

If you are exporting models and not brushes, you can do lots more, such as single floating faces, concave objects, proper UV mapping, etc...

Finally a WARNING about the 3DWarehouse.
1: Most models in the 3DWarehouse still have copyright protection the same as most user created content. Ask for permission before use.

2: Many of the models in the 3DWarehouse are NOT game quality. They will often be built in a messy fashion with too many polygons, unconnected lines, massive textures, improper scale, etc... Often the model rating will help to guide you to well made models. Some even not built to scale.

3: The 3DWarehouse however IS a great place to get references for making your own models.

According to this page:
http://developer.valvesoftware.com/wiki/SketchUp_Source_Tools
the SketchUp plugins are now included with the SourceSDK and L4D SDK. They are for sure included with the Left4Dead SDK, all you need to do is own a copy of L4D.

Documentation on the general use of the plugins comes with the SDK.
I don't know programming but it seems like there should be some ruby scripts that could be written to aid with making brush objects for hammer. Specifically making objects into convex groups, and checking for errors. Something I with the exporter could do on its own.

The simplest way for me to model for hammer is to model as normal in SketchUp, clean up the model for any stray lines, revered faces, or broken lines (that don't meet two other lines).
I have explained a lot of this on page three of this thread:
http://forums.steampowered.com/forums/showthread.php?t=922563&page=3

I am working on some tutorials right now. Once you know the exact process and what to look for making these models is very quick.

In the mean time here are some more 100% brush models I have been able to bring into SketchUp in a short time. Most of them taking just one evening from concept to in-game. All these models use

[img]http://farm4.static.flickr.com/3467/3771577728_5cf96da78d.jpg[/i

More photos here:
http://www.flickr.com/photos/zapwizard/sets/72157619140531291/

Exporting models instead of brush work is much easier. You can use just about any shape and method you want in SketchUp. The game also preserves the UV for models, but not for VMFs.

The trick comes with physics objects, you basically make a new group that is all convex brushes, 100% smoothed and export that as your collision model.

I made this sleeping cot in less then 30 minutes and had it working in game with physics and all.
I don't have a in-game screenshot though. I re-used a sleeping bag texture from the game so I didn't have to make my own.

Hey, update here:
Valve has released two offical SketchUp plug-ins along with their Left4Dead SDK.
The plugins also work for other Source games, but you have to own L4D.

One plugin lets you export 3D Models, the other world brushes.
It also lets you assign in-game textures and objects if you simple name them properly.

Here are some tips off the top of my head:
1: To make a hammer-style brush in SketchUp group together a block, or group of polygons (if convex) together. If you make a simple 6-sided block as a group or component you can further edit it in hammer the same as any native hammer brush.

2: Use the texture naming schemes given out by Valve. I have even gone as far as to import all the textures and proper names into the SketchUp library so I can apply them easily.

3: Models are much more flexible, but also require more work depending on your texture use. Models can have single-sided faces, and concave surfaces.
Collision models are easy enough to make, but using a grouping of convex blocks, all with default materials and all 100% smoothed.

4: Ensure you don't have any errors in your model, that is lines that don't meet at a corner, stray lines that don't meet another line, or reversed faces. There are some ruby scripts to help clean this stuff up automatically. I will try to find the links.

5: SketchUp defaults all curves to 12 sides, and all circles to 24. You can change this default number by selecting the tool and typing a number in either right before or after you place your curve. This is the NUMBER one reason for high-poly models in SketchUp.

6: Know the limitations. For example the value brush importer doesn't have any UV or texture scaling numbers, so you have to tweak these in hammer. It however does work well for models.

The followings is all part of a campaign I am working on:
http://www.l4dmods.com/forums/viewtopic.php?f=80&t=3097

Here is a model I made in about an hour using SketchUp and only the native materials inside Left4Dead. The model is 100% brush work with some props added.

Reference photo:
[url=http://www.flickr.com/photos/fredericksburg/2939995054/:1n4q50gn]

[/url:1n4q50gn]

Inside sketchup, and also properly geo-positioned
[url=http://farm3.static.flickr.com/2572/3744142295_35c5c97ea5_o.jpg:1n4q50gn]

[/url:1n4q50gn]

Inside the game engine, with a few quick props added.
[url=http://farm3.static.flickr.com/2467/3744929850_da9074acb2_o.jpg:1n4q50gn]

[/url:1n4q50gn]

This is a much larger building, which currently only exists as a model, and will be converted into 90% brush work, and 10% model detail. Again this model uses only textures that were already in L4D.

Here is a photo of the real building:
[url:1n4q50gn]http://www.flickr.com/photos/mcgervey/3299027241/in/set-72157613789552413/[/url:1n4q50gn]

[url=http://farm4.static.flickr.com/3593/3600025498_293a9943df_o.jpg:1n4q50gn]

[/url:1n4q50gn]

[url=http://farm4.static.flickr.com/3642/3604975195_70cd83aa97_o.jpg:1n4q50gn]

[/url:1n4q50gn]

[url=http://farm3.static.flickr.com/2434/3663320760_137d4e66f3_o.jpg:1n4q50gn]

[/url:1n4q50gn]

[url=http://farm4.static.flickr.com/3654/3662518771_0c17d37249_o.jpg:1n4q50gn]

[/url:1n4q50gn]

Something I was working on today

Wall-E is hours of work getting a good model that would be optimized in for a game. He is still far from finished though.
I used parts from a few different Wall-E's in the 3D warehouse.

sella, FarCry2 does not have a sandbox editor (It was not made by Crytek)
FarCry2 only has a very basic sim-cities style map editor.
SandBox2 from Crytek is more of a whole game editor.

Pixero, once you have your CGF in the \Game\wherever folder, place a "brush" entity.
Then change the model of that brush to the CGF you created.
Though my work today I discovered that components don't export, but groups do.
Wall-E up there is made of 22 separate components exported and converted.

I have exported items with multiple components with no issue. Some more complex models I exploded and then cleaned up. Make sure and purge any unused items before export.
A messy model that uses lots of intersecting hidden lines may not work well.

Ideally a game ready model should be a solid model with no hidden lines, no lines that pass through faces. Basically the same tips that Google shows in their "How to model for Google Earth" tutorials. All texture dimensions need to be a multiple of 64 along their dimensions (128x128, 256x512, etc...)
Crysis uses .DDS (direct draw) textures, so I convert all the textures using Paint.net.
When you first import the object it won't have any textures.
In SandBox2 open the Material Editor, select "get current material"
You will see a list of material id's, inside there will be a texture path.
The texture path will end up looking like "file://..images/texture0.jpg"
Change that to the correct path for the .dds replacement.
For portability to other people's computers, you should keep your textures and model files under either "crysis\game\levels\YOU LEVEL\objects" or in a similar \Mod directory.

I suggest you try exporting the spitfire linked in my thread first to get the hang of it.

Just a reminder: If you want to try this out without buying, the Crysis demo comes with the full editor. (But not as many 3D assets as the full game)

The editor is not updated for Crysis warhead, although it is apparently coming sometime.
However you can import most of the Crysis warhead assets into the current editor.

The biggest thing I am going to be using SketchUp for is buildings and props, which is a huge part of any game.

Update for you guys: There is now a much easier and faster way to import SketchUp models into SandBox2 (Crysis engine)

The program is a basically a Calloda to CryEngine2 converter.

See my thread here:
http://www.crymod.com/thread.php?postid=394096#post394096

Source model:
http://tinyurl.com/5gjd42

Links to tutorials on SandBox2:

http://doc.crymod.com -Official manual
http://wiki.crymod.com -Wiki
http://www.crymod.com/tutorials.php -User made tutorials (all of my tutorials are in here)

There are also lots of other third-party sites like the one mike posted.

Richard, that screenshot is in-game. Crysis handles large areas, real-world scale and lighting very well that is why it is so attractive for visualization. The vegetation handling is also second to none. (So far)

Also the editor for SandBox2 is done in-game, meaning fully rendered, and it takes only a keypress to move into the map in a interactive form. Many other editors are just that: separate editors that allows you to make a map, compile it, and then launch it separately in the game.

I have only dabbled a little bit in the Source editor. It is easy to use also but not quite as powerful if you want something that is a perfect real-world match, and it also doesn't do massively large maps. In 64-bit mode SandBox2 map size is only limited by your CPU horsepower and memory.

@plot-paris, See below on the terrain, none of the actual in-game models other then the HDTV and flashlight posted above are imported SketchUp. However I used SketchUp and Google Earth in making my map. And I plan on using SketchUp to make in-game models once I get a good importer flow working.

For my first map (Castaway) I extracted satellite photos in 1:1 scale from google earth.
I have a series of video tutorials on how to do this here:
http://www.veoh.com/channels/ZapWizard
But the heightmap (the elevation of the terrain) was all done by hand, and all the terrain was re-painted in-game using the satellite photos as reference.
Here is my flickr photos on that project:
http://www.flickr.com/photos/zapwizard/sets/72157603074021169/

For my second map (Zion) it was a bit easier. Since the area is located in the US and is a national park there is hundreds of pages of data on the USGS website. Specifically I used a 1 meter resolution satellite photo (USGS) of the area which was better quality then Google earth had on the area.
Then I downloaded a 2-meter resolution height map from the USGS website.
Just with those two components I was able to get the images above.
The how-to on importing real-world height maps is here:
http://www.crymod.com/thread.php?threadid=17539

Once you add water, roads, and vegetation the results are very close to photo-real:

Compare to: http://www.panoramio.com/photo/3932425

My flickr set for this project is here:
http://www.flickr.com/photos/zapwizard/sets/72157605714135417/

The XSI mod-tool is about as easy as it gets. All I had to do to get my models in was to tweak the textures names in the XSI tool and then pass it on to SandBox2. I would do more but the plug-in isn't working on my newest PC.

Is should be pretty straight forward for someone to write a model converter as the full SDK for SandBox2 is out. I just have no skills in programming that type of stuff.

FarCry2 does look to have a great engine from the videos, however just FYI the engine is not developed by Crytek, only the license to the story was bought from them.

From a quote on the FarCry2 editor:

@unknownuser said:

We can't ship our real production editor - it's just impossibly complicated - so the version we've built for the public is a very quick and super user-friendly level editor that allows people to build maps for multiplayer very, very quickly in a few hours," said Hocking. "It uses all in-game assets so it's as beautiful as the game, unless you make a giant pillar of rock 500 metres high and don't texture it or something - then it's ugly - but that's up to you.

Where as with CryEngine2 they have a full SDK, and nearly every tool used to actually make Crysis was given out to the public.

Now I know we are not talking about making games here but realistic real world scale visualizations, but I have found nothing that is as easy and powerful as SandBox2.

I have my entire home modeled in SketchUp, I am thinking about making a demonstration map inside SandBox2 using my house as a model in the editor. Also my work is interested in using the game engine to setup virtual walkthroughs that allows a customer to see how our products work inside their home.

I have used SandBox2 combined with Google Earth to make two maps based on real-world terrain.
My first map, called Castaway has the same outline and basic terrain as the island where the movie Castaway was filmed. The island is 1:1 scale with the real-world island, and I used images from Google Earth as reference to paint the terrain.

On the map I am working on now I am actually using eight square km of real-world terrain. Specifically Zion's National park. The terrain is perfect 1:1 scale in elevation using USGS data. The textures is also nearly perfect using 1 meter resolution USGS satellite photos.

Here is the terrain in Google Earth:

Here is the terrain in SandBox2 after only a few hours work:

First off, long time forum lurker...but long time sketchup user.

I am very interested in getting a SketchUp to SandBox2 (Crysis) converter working.

If anyone is interested you can convert easy enough from SketchUp in to SandBox2 using XSI ModTool as a in-between.
SandBox2 is free with the Crysis demo (Although you get more with the real-game)
SketchUp free version can be used with the XSI ModTool using Google Earth 4 KMZ files.
And XSI ModTool is free.

I have used SketchUp a few times to bring in basic custom objects into the popular map I made in Crysis.

Text:

Flashlight:

HDTV:
http://www.crymod.com/thread.php?threadid=19058

I have a (Very) basic how-to here:
http://www.crymod.com/thread.php?postid=178946#post178946