Using patches for terrain or anything which should be clipped, is usually not recommended. Reason is the bad clipping, you might get stuck or fall through. Or some parts disapear completely, making holes in your terrain.
So we need a way to properly clip the patches. We can do this by converting the patch to an ASE, and then let q3map2 clip the ase. At this step you either have a good terrain, or one which has bugs. As you cannot see how its clipped, the last step is to decompile the compiled ASE. And this will give you brushes.
Now you will be able to see where the terrain is bugged in the editor. It also allows to tune the terrain further. To either use the generated brushes and tweak them, or modify the patch mesh - and go through those steps again.
In detail, first step
Make the terrain with patch meshes, since one patch mesh can either be 15x15 or 31x31 (netradiant) width, it will probably need to multiple ones. The patch meshes need to be aligned perfectly with each other.
All control points need to be on the grid (this stuff gets converted to a brush later!).
Always re-disperse the patches, unless the extra detail is really wished - but that makes everything more complex, as it will be converted to brushes later.
Redisperse Intermediate Cols - Shift + Control + E
Redisperse Rows - Control + E
Now once the terrain is textured and ready. It can be in a map with all the other stuff when making it… but for the next step it needs to be put it in a separate map.
Second step
Copy the patch meshes for the terrain, into a new map, add a hollow caulk box around it, and a player spawn - so that it can be compiled with -patchmeta; Check here:
http://en.wikibooks.org/wiki/Q3Map2#Creating_an_.ase_model_out_of_brushwork
Subdivsion is of no use here, if the patch meshes have been properly re-dispersed.
Third step
Include the ASE as misc_model in a new map with a hollow caulk box and a player spawn, so that it can be compiled again.
With NetRadiant q3map2, there are 3 options for extrusion of the ASE.
http://dev.xonotic.org/projects/xonotic/wiki/Complete_list_of_entity_keys
spawnflags: 1 = in SoF2, append a _RMG_BSP suffix to shader names instead of _BSP
spawnflags: 2 = generate clipping brushes from the model
spawnflags: 4 = force this model through meta surface merging
spawnflags: 8 = when generating clipping planes, perform extrusion using the original normals from the model instead of per-triangle best axial normals
spawnflags: 16 = when generating clipping planes, perform extrusion using only up or down pointing normals (ideal for terrain))
It needs spawnflag 2+4 + (8 or 16 or none)
none, 8, 16 each of these does extrude the ase in a different way.
If the terrain is flat… well almost flat, Spawnflag 16 is best.
Spawnflag 8/none is better when the terrain is no so flat. But it will be troublesome, and have overlapping stuff probably.
A meta compile of this, should give a bsp with a clipped ASE. Now that terrain is kinda buggy - you will fall through at some spots and get stuck at others. If your lucky the terrain is already perfect. The better you put all control points on Grid, the better the result.
Fourth step - yeah we are not done yet :stroggtapir:
Now we have to decompile the compiled ase - NetRadiant’s q3map2 will conserve the textures.
http://en.wikibooks.org/wiki/Q3Map2#Decompiling_into_a_.map
This will give us a lot of brushes in triangle form. And some of these brushes will be broken, and some others maybe missing - e.g. in the ASE there was a triangle. Now you can either modify your patch mesh - and go trough the process again (write a batch script - lol)… or you can manually add/fix these brushes.
In any case its the fastest way to create large ‘natural’ structures with brushes.
You will have to take extra care of brushes where the extrusion does overlap.
If you have for example a wall with a edge, and that edge is below 45° …
/\ An edge like that in the ase looks fine (imagine the left / is a face and the right \ is another face forming the sharp edge in the corridor…)
Once the ASE gets extruded, each face gets extruded (with none/8) in a different direction, and the caulked extrusion will stick out of the face… and block players… Solution is to mitter the caulking.
I hope I explained it more or less correctly…
Well with these 4 steps, you can make terrain very fast. And adapt it in the Editor perfectly to your map. You can also add a more detailed patch in the terrain… not all need to have same ‘resolution’ … the cycle spawnflags: 4 = force this model through meta surface merging
should take care of that and add splits or remove if possible…
Btw, once you have the ASE … you can actually open it in a 3D modeler and edit it further … but the extrusion results might be even worse cause it will probably not be on the Grid.