I used a LIDAR point cloud, imported it in meshlab, sampled (from 9 million points to about 1) and reconstructed a mesh for it, set normals, exported as OBJ, then imported it into Blender 2.76. I have Cycles Rendering on, made a simple material in the node editor with just a Diffuse BDSF shader with a flat color and no roughness (0.1 roughness looks the same). I get this wierd result:

This is in Render View Render View Material view looks fine.

What am I doing wrong?

Here is my .blend

  • 1
    $\begingroup$ Looks like either z-fighting or messed up normals. Try [W] > Remove Doubles. $\endgroup$
    – PGmath
    Jan 7 '16 at 19:03
  • $\begingroup$ Remove doubles didn't do anything. While I did find some messed up normals, there's very few of them (only in face, not in vertex or edge), and generally are nowhere near the problem areas, which are ubiquitous. These "tears" aren't even in the same shape as the triangles which make up the surface. Selecting the faces under these black tears and flipping normals does not eliminate them. Most normal or meshing errors I've found and corrected don't present themselves like these artifacts at all, and any manipulation to amount of vertexes, overlapped lines, etc do not help. $\endgroup$ Jan 7 '16 at 22:27
  • $\begingroup$ Does it still give these artifacts when actually rendered (not just in render view)? $\endgroup$
    – PGmath
    Jan 8 '16 at 14:18
  • $\begingroup$ It does still have them when actually rendered. $\endgroup$ Jan 8 '16 at 17:10
  • $\begingroup$ @PGmath I still haven't found an answer for this. $\endgroup$ Jan 26 '16 at 18:36

The problem is caused by the fact that although the terrain origin is at (0,0,0), the real mesh is still very far from it.

So it seems you have to use a very large clipping range (1000000 in your case), which allows you to see objects, but reduces the depth precision. This is a known limitation of all softwares using OpenGL.

To fix it, you can:

  • Increase the start clipping.
  • Decrease the end clipping.

However, you may also have to scale the objects to see it again. (And, in your case, I would suggest you select the terrain then ShiftCtrlAltC > Origin to Geometry, to relocate the origin from afar. Then move them back to the world center.)


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