Facing a terrain project,where should we 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 roads is modified ,all things connected with them will have to be adjusted.For example,if the curbs of a road is created first 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:
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 partial borders to create polygons,StitchVerts and Triangulate(Faces) can subdivide polygon faces.If you are using the Lite version ,advConnectVts is an alternative.
More quickly,we can use StitchPoly directly to connect the terrain and the road.
Use StitchVerts connect roads and terrains
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 .
Create terrain with Slice
the way is also suit for 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 original terrain.So,you need not to stitch them.
Use MoveVerts re-construct terrain
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(cut vertices perpendicularly to one edge),CutByAgl(cut vertices on borders along angular bisector ),Cut2Verts(cut between 2 vertices),Connectverts and StichVerts,and so on
Cut perpendicularly to edge
Cut along angular bisector
Connect two vertex team
Make slope and smooth road
Such a tool is indispensable:when vertices of surface fall to 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.
To present road levels and get a natural appearance,the section of the road need to keep horizontal,and can’t be sticked to terrain like clothes .So the tool should be, with selected edges on one side of road and several vertices at special elevation,which can output the smooth transition of curve and meanwhile map this side of the evelation data to the other side,thus we can get the road to transit smoothly between elevations.
you can use smoothroad(linear),SmoothRoad(curve),SmoothRoad(npts),SmoothRoad(blur) to complete this work.
Use SmoothRoad(blur）to smooth road
The article describe only several main issuses of landscape modeling from the outer frame,it should be as a main direction.Hope that every readers can get desired help and have a good beginning.