3D Terrain Modeling Problem

[deadfly]

Hi,

A client has asked me to do something a little different than I usually do and that is a 3d terrain model. All has gone well so far, but when i render I get some funny black holes in my mesh. (see attached photo(please excuse the bad image map))

Anyone had this problem before, or know how to solve it?

Here is my work flow, if its any help.

survey data from a .txt file.
imported into Autocad 2008 with TerrainCAD plug in.
Mesh created with TerrainCAD
Imported to 3ds Max 2008 & rendered with Vray 1.5

Thanks in advance!

[WAcky]

Hi Joel,

Without seeing your wireframe mesh I cant really see whats going on.

Perhaps try looking at the first 3 tutorials listed here. There is a section on optimizing your terrains to reduce this type of artifacting.

Good luck!

[BrianKitts]

how was the terrain model generated?

my first guess would be that the normals are flipped on just those black faces. Use an edit poly modifier on your terrain select just those bad faces and flip their normals to see if it corrects the problem.

If it's not that my second guess is that it's just bad smoothing applied to the mesh, the vertices might be pulled too much in those locations. In which case I would try using the edit poly modifier and with the paint deformation tool, select relax and just paint up the area a bit to smooth it out.

[slanier]

I have had this happen before when using terrian creation from splines. It's usually faces overlapping or having drastic elevation changes.

When you use the terrain function to create geometry, MAX will create a TIN, Triangluated Irregular Network.

This is basically MAX doing anything it can to create a congruent mesh out of the linework that you present.
This can cause geometry issues, because the mesh is never elegant.
I would go back through the model especially in areas that are coming out "black" and see if you can't do a little clean up.

More times than not, the areas that turn out black for me, are usually areas where tons of geometry comes to a single point.

It's frustrating, but one way to reduce that is to reduce the number of points or steps in your splines. If you can reduce the verts in your splines, your TIN terrain will not be so dense.
Hope this helps.