The usual way of making brushes to make an object doesn't really work here, so instead people use a third party tool.  One is EasyGen, which I don't use, and another is GtkGenSurf (a plugin included within Radiant) which I do.

I haven't tried EasyGen so I can't comment on it.  Also there's a new terrain-generating-kid on the block called FATE, which looks like it will be really good when finished.  As I haven't used it I will stick to explaining how to do things in GtkGenSurf.

GtkGenSurf will generate an area of terrain using lots of triangular brushes, like the box Toblerone comes in, with one end face the required texture and all the rest as caulk.  You tell GtkGenSurf the area dimensions, the required size of triangles, the textures to be used and the contours you want and hit the Go button: GtkGenSurf then produces the terrain mesh, already grouped and ready for you to slot into place.

The approach I take to making terrain is this:

• Identify the area in the map that needs terrain - it will need to be rectangular although when the terrain is generated you can always chop away the stuff you don't want.
• Make the dimensions multiples of 256 unless the terrain area is small, in which case you could use multiples of 128 or 64 etc.  The smaller the triangles you create, the more of them there will be.  More triangles means nicer looking, but higher demands on the PC to draw them.  I have always used 256 to date.
• I give GtkGenSurf a rough description of the required geography and do the first generation.
• If it looks roughly ok in Radiant, compile it and go run around in ET.
• Note down the imperfections, like this bit is too tall, that bit is too steep, etc.
• Go back to Radiant, delete the terrain, refine the description to GtkGenSurf and try again.
• Repeat as many times as necessary to get it mostly right.  This might take 20 goes or so.
• For fine tuning I drag individual triangle vertices about in Radiant.  This is very tiresome and to be done last.

It can base the undulations on the forms of waves, cylinders or fractals, or from a bitmap which specifies how the lumps and dips should be laid out.  In practice I've found the bitmap method to be the most useful, so that is what I'll describe here.

You can create a rectangular bitmap, ie a graphical file of type .BMP, and by colouring the pixels in it in varying shades of black to white, tell GtkGenSurf how you want the terrain to rise and fall.

The tutorial map is 2048 * 2048.  We'll make the terrain mesh size 256 units (1 box  in grid scale 9) as this will be fine for the demonstration.  2048 / 256 is 8, so the size of the bitmap will be 8 * 8 pixels.

The tutorial map currently has lots of stuff in the bottom left quarter, with the rest more or less empty.  We'll make the empty 3/4 a bit hilly, and make the bottom 1/4 flatter.

Use Paint Shop Pro or any graphics editing software to create an 8*8 image.  Make it greyscale, ie 256 shades of grey only.  A coloured BMP will not do.  Fill it with black.

Black represents 0 height.  White means 255 high.  The lighter the grey the greater the corresponding height, as interpreted by GtkGenSurf.

Make the top & right area some dappling of grey to give some slopes there.  Here is a zoomed in image of an example 8*8 BMP.

As can be seen I've left the bottom left corner flat for now, to avoid some of the features we've put there disappearing into the terrain.

Save the file as a .BMP file type, eg tutorial.bmp.

Zoom/move the 2D view so you can see the whole map.

Click Plugins/GtkGenSurf/Ground Surface...  and this window opens up.

Make sure that:

• "Quake 3 Arena" is chosen as the Game
• "Ground surface" is selected for Orientation
• "From bitmap" is selected for the Waveform
• A "Roughness" value (how much irregularity should be introduced to the undulations) of 50 is fine, and pick any random seed you fancy (a starting point for the random numbers used - who cares really).  With a non-zero roughness it means that areas you've specified as black, ie flat at ground level, won't actually be completely flat, there will still be little curves and bumps.
• "Antialiased lines" ticked is nice

We must enter the map extents, ie tell GtkGenSurf the size of the area to create terrain for.  Seeing as we are using the whole map and we created the map with the lower left corner at (0,0), this is easy: the bottom left is (0,0) and the top right is (2048,2048).

As it happens, the Divisions default is x=8 and y=8, which happens to be what we want for our 8*8 terrain mesh.  If the map had been 4096*4096 and the box size were still 256, you'd enter 16 and 16 here.

Browse to the BMP file you created.  Don't worry about the map color boxes, they can be used to scale the undulations to increase the height range above 256, but we don't need that now.

Click the Preview box.  This will show you what the geography will look like.

Click the Texture tab.

The Surface texture is the main texture that GtkGenSurf will use when it makes the terrain.  You can change this to the texture you want.  While I'm making the Ludendorff map I am using some grassy dirt texture.  You should pick an organic texture, something like grass, dirt, snow, gravel, sand etc.  There are some good grassy choices in the textures/temperate_sd set, so for now I suggest you choose master_grass_dirt3.  There is no "browse" option, so you have to type it in.  Don't put .tga or .jpg at the end, just give the texture name.

The Other texture should be left as caulk.

The Steep texture is the texture to use for steep angles, defined as 60 degrees or more unless you change it.  You would make this either the same as the main surface, or if you wanted say hills to be grassy mainly but rocky on the steep slopes, you'd give a rocky texture here.

Make sure the "Use detail brushes" box is ticked.

The main window of interest is the preview window.

We can change the height of any point (except the yellow ones) by clicking on an intersection, and then entering the required height value.  If you enter a value in the Range Affected box, nearby points will be adjusted too.  As the adjacent points are 256 units away, you'd enter say 512 to affect your 2 nearest neighbours in all directions.

Click on a point and increase the height value so you can see the effect of your adjustment.  I have made an exaggerated adjustment here to make it obvious.

I don't really want this spike, so I can release it by clicking Free and it will return to its original value.

What you will find is that it is hard to equate where you click on the grid to where in the terrain you are actually affecting.  This is a pain.  Sometimes I flip the image upside down with the Elevation and spin it around with the Azimuth to get the left and rights to match up - but then the top and bottom are reversed. :(

It's trial and error and you must pick the view orientation that makes the most sense to you.

I'll repeat the point adjustment, but this time with a Range of 512.

You'll see how the neighbouring points are dragged upward.  This is neat and goes some way to compensating for the aggro you'll have in trying to work out which point is which...

You can adjust multiple points simultaneously by ctrl+clicking on the grid, and you can do rectangular ranges by shift+clicking.

For now we'll just leave it to the default values.  If you've made the grid a mess, click Free All.

Your view should look something like this:

For the sake of simplicity we'll just move the floor down a notch.  Get a 2D side view.  Change to grid size 7.  Select the old floor brush and move it down one notch.  Click on the hull_caulk texture in the textures window to give the whole brush that texture - we don't need it to be drawn as snow any more.

Press ESC.  Select all 4 of the surrounding wall brushes, and extend them down one notch to meet the bottom hull_caulk brush, thus making the solid surrounding cube again.

Press ESC.  Your view should now look something like this:

If you generally don't like how the terrain has come out, rather than specific detailed parts which we could fix by hand, select and delete the terrain group and go back to GtkGenSurf.  It will still have your details so you can just Fix Points differently and try again.

If though you have exited Radiant, GtkGenSurf will not know your terrain settings, so you will first have to use GtkGenSurf's Open... button and tell it to open "tutorial.ini".

An important detail to note is that there is a chunk of terrain inside the building.

It's at this point that it starts to become clear why we have taken such trouble to make our buildings line up along big grid lines where possible.  Choose grid size 9 and get the overhead 2D and you can see the terrain triangles that fall within the building.  There are 6 of them.

Select all 6 triangles in the 3D view, by first hiding the intervening floor brushes, and delete them.  Press shift+H to reveal the floor brushes again and it should look like this:

This will have revealed some gaps around the bottom of the building, as shown here:

The better solution to all this is to manually adjust the triangles in Radiant, but we'll come to that in the next lesson.  For now just select all the floor brushes again and extend them downwards in the 2D side view using grid scale 5.  This will still leave a problem with the door, because the terrain comes up the door a bit, and you'll see its caulk when opening the door from the inside.  We'll fix all this in the next lesson.

Save, compile and run around in your new hilly environment.

By the way, when taking screenshots from ET you usually have to increase the brightness (eg 40%) and contrast (eg 20%) otherwise the JPG looks too gloomy.

Whether or not you can plant landmines will depend on the texture you used.  If it's a shader with landmines enabled, you'll be able to plant landmines.

A neat way to see if a texture is actually a shader (ie there is a bit of script-like information for it which gives it properties instead of just being a picture) is to shift+click on the texture of interest in the textures window.  Make sure you have pressed ESC first or you will apply the texture to any selected brushes/faces. If the image is a plain texture, Radiant will report something like: ERROR: textures/egypt_floor_sd/block-16sq is not a shader, it's a texture. If it's a shader, ie there is an entry for it in a shader file, Radiant will open the shader file using Wordpad or whatever you have associated with .shader file types.  Find the texture name in there and see if "surfaceparm landmine" is given under it.  If it is, you can plant landmines on faces with this texture.