Facing a terrain project,where should you begin ?It is really confusing, but there is still one thing we can confirm :All works of the terrain modeling base on some roads,that is to say that all things is meaningful only when the roads is fixed. If the road is modified ,all things connected with it will have to be adjusted.For example,if the curbs of a road is first created  and then you want to change the elevation of the road,previous work will be wasted.So,the most logical and resonable steps should be :At first ,build your road as accuratly as possible ,then think about how to add new faces to connect the roads and the terrains.This is also the basic thinking that TerrainAxe was designed basd on.

Generally,three issues are the most focused by 3D modeling artists:

Good topology

Make slopes and smooth roads

Connect roads and terrains

First of all,we talk about the most concerned question for 3D modeling artists :how to connect roads and terrain

Connect roads and terrains

There are two main ways to connect roads and terrains:

For an existed terrain object(such as a terrain mesh built from contour lines or some DEM data),thinking about the work flow:first ,delete the faces covered by the roads,then we can get some borders,with the borders and that of the roads ,create a big polygon face and subdivide it,then we will complete connecting.

In TerrainAxe,CapEdges,FreePoly can use an unclosed border to create a polygon,StitchVerts and Triangulate(Faces) can  cut polygons.

We can also use StitchPoly directly to create polygons to  connect borders of  a terrain and a road.

2.For those areas enclosed or semi-enclosed  by  roads,maybe the original terrain is missing or un-useful,a new terrain need to be re-created. Thus you can cap these areas to create a new polygon,then use Slice to cut and get grid-like topology,then relax them or paint desired appearance with 3dsmax's brush tools .

the way is also suit for the first situation.If you don't like the topology created with contour lines,you can use MoveVerts to conform vertices of the grid-like faces to the original terrain.So,you don't need  to stitch them.

Topologize

Topologizing is very important.To present accurate slopes and road levles, topologizing or re-topologizing   is necessary.There are some requirements for topologizing:

A road should be made up of regulate quad polygons as much as  possible,as shown  below in left picture;Some ground pavement need some cutting operations to make the polygon topology more reasonable;

Narrow and long triangles should be avoided as much as possible. The more reasonable topology, the better the effect at render time, as shown below in the right picture.

To meet the above requirements,many cutting operations are needed.In TerrainAxe ,there are many cutting tools to such as CutPerToEdge,CutByAgl,Cut2Verts and StitchVerts,and so on

Slope modeling and road smoothing

Make a Slope

Such a tool is indispensable:when vertices of surface fall to a slope,only z coordinates are modified but xy coordinates keep unchanged,that is ,make vertices align to slope plane along Z axis ,or the structure in top view will be damaged.MoveVerts can do this.

Smooth Roads

To present road levels and get a natural appearance,the section of a road need to keep horizontal,and can't be sticked to the terrain like a clothe .

So an ideal tool  should be able to output a smooth transition like a curve and meanwhile be able to  map  the evelation data of one side of the road to that of the other side,

When smoothing a road ,continous  edges  can be used to represent a range of  the  road  and the vertices with different z coordinates  to express  different  elevations 

you can use SMRoad(linear),SMRoad(curve),SMRoad(npts),SMRoad(blur)  to complete this work.

SMRoad(Splines)  uses a more advanced way to smooth a road in which you can ajust knots of splines to control the transition.

The article describe  several  main issuses of terrain modeling from the outer frame,it should be as a main direction.Hope  readers can get desired help and have a good beginning.