i'd like to create a really huge terrain. it seems to me that 3dgs doesn't support 1 huge piece of terrain but rather many pieces of terrain 'stitched' together. the problem is that i can't find a software to do this stitching or splitting and even if so, there're always visible seams and possibly collision detection errors as a result (such as terrain height queries at the boundaries).

can anyone provide any advice on this?

Correct me if I am wrong but with the latest 6.4 update chunked terrain removes all limits on terrain size.

but the isn't the issue with med? i tried creating a terrain with the maximum values for triangle size and vertices but it simply crashed.

You need the 6.4 public beta update for this. With 6.31, you'll need to have at least 4.7 GB of memory just to handle it because of a design flaw in MED. This flaw (originally reported by me when the 6.40.0 update was finally available) has been fixed in the latest MED (since at least 6.40.2). Another possible cause is that the terrain is using more than 65,535 vertices, the limit of DirectX and MED isn't designed to cope with this. The highest possible is 500x500 vertices which needs slightly over triple that limit.

The absolute largest you can make a terrain is 257x255 vertices (or 256x254 tiles as I often think of it as).

You may also try using model terrains instead of HMPs.
First, create them all with same size say 20000 x 20000 quants,
place them all in the centre origin (postion : 0,0,0) in WED,
then set their skill1 for x-axis and skill2 for y-axis like :

terrain 1 = skill 1 : 0, skill 2 : 20000
terrian 2 = skill 1 : -20000, skill 2 : -20000 etc...

Code:

---

// assign this action to all terrains
action positionTerrain
{
  my.x = my.skill1;
  my.y = my.skill2;
  my.polygon = on;  // sensitive of collision

  // option : make them visible or invisble within
  // the camera view distance to increase fps
  while(my!=NULL)
  {
	if (vec_dist(my.x,camera.x) < camera.clip_far)  // play with camera.clip_far
	{
	   my.invisible = Off;
	} else {
	   my.invisible = On;
	}
	wait(1);
   }
  
}

---

It is much better than drag and place each terrain in WED.

Check this out: Infinite World. Some thoughts to this theme.

if i use a huge model instead of hmp, will the engine still 'chunk' it?

is there a tool to help create 'skirts' that prevent z-fighting and also holes in the ground when someone puts together several tiles?

Chunking only applies to HMP terrains, not MDL terrains. However, with the flexibility of using MDL terrains, you can get faster rendering, greater flexibility in shape, and several more advantages. For holes in the ground, only MDL terrains support that.

mdl terrain is not faster. mdl uses uv-sets to apply textures. terrain uses only a plane projection from above. Terrain vertices all have same size. So terrain can render much faster.

But you could program your own clipping system or use the LOD system of Gamestudio for mdl tiles of your terrain. But when you want to do that then it is better to buy IceX2 that already does all that for you.