Updating terrain models

I have been trying to find a easy answer to this problem, perhaps there is non but wanted to put it out to the community to see. What is the best way to update a terrain model if the design changes without having to remodel the whole site again?

Say you have a project that includes some buildings , parking areas and landscape. Modeling this to 3d by extruding curbs, walks, planters and any land forms creates a mesh with components of the above mentioned… If the design changes significantly or you want to change out an area of the landscape to a new design it is pretty much impossible to insert this into an existing landscape mesh without destroying and patching it together again. It seems easier sometimes to just remodel the whole ground plane. Is there any good way to do this if you don’t know what is going to change in the future? perhaps in the initial set up?

Ah the joys of working with terrain in 3D. Long story short is to create boundaries defining areas that may change prior to modeling everything. That way each ‘zone’ can be grouped or made into components independent of one another. That won’t solve everything but it’ll limit the damage when (not if) something changes.

If you haven’t set it up in advance to change, then you can ‘clip’ out areas at any time. See a simplified example:
1.) Draw a flat boundary directly above the terrain that encompasses the terrain area that needs to be revised.

2.) Extrude the boundary tall enough to cover the depth of the slope and move down into slope.

3.) Make sure that your extruded boundary is INSIDE your terrain group and then intersect with either model or selection.

4.) You now have an area that represents the extent of change on your surface. This red area in the example can be grouped and frozen (if needed later) or deleted.

5.) You now can safely change the surface / terrain within the boundary. Here it’s shown as a component given that often there are lots of objects on the surface so you can set your component fade to hide, turn off surface objects layers, or, like shown copy and work on the new area off to the side, watching as the boundary area updates in place.

Same technique applies to working with objects on the surface. If you haven’t organized things to change in advance, you can clip things like curbs or retaining walls where needed and re-model just affect areas only.

Post some images of your progress to help share your opportunities and constraints with others :wink:

***UPDATE. Some people who read this will say it’d be easier to drape the change boundary vs extruding and intersecting but in my experience, the more complex the surface, the more likely that draw can’t complete a closed loop - whereas intersect almost always can.


It’s worth noting that, depending on where or how you obtained/created your terrain, quite often the terrain mesh is a triangulated grid.
This means you can turn on hidden geometry and easily select sections. So if you keep a copy of you original terrain you can copy and paste new sections as needed. By leaving it in place on its own layer you can even use Paste in place.


thanks, yes these are all good tips. sometimes the TIN does save time selecting out a few triangles. I’ve tried the clip out option before, sometimes it works sometimes it doesn’t. I think the complexity of the model affects this, probably best to copy out the terrain to a separate clean file and try it there. That may make it easier for the computer clip/intersect with a less complex model.

Yes I forgot to mention that if the terrain mesh is large and complex, make it a component and do a ‘Save as’ and then work on it in its own file…then just ‘reload’ into main model after making changes. If you post model/screenshots we can be more specific with addressing your particular mode’s challenges.