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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

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Gabriel Ortiz Duran
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    Looks like either z-fighting or messed up normals. Try [W] > Remove Doubles. – PGmath Jan 07 '16 at 19:03
  • 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. – Gabriel Ortiz Duran Jan 07 '16 at 22:27
  • Does it still give these artifacts when actually rendered (not just in render view)? – PGmath Jan 08 '16 at 14:18
  • It does still have them when actually rendered. – Gabriel Ortiz Duran Jan 08 '16 at 17:10
  • @PGmath I still haven't found an answer for this. – Gabriel Ortiz Duran Jan 26 '16 at 18:36
  • It would help to have the .blend file to look at. Try uploading it to Blend Exchange and editing the given link into your question. – PGmath Jan 26 '16 at 18:38
  • @PGmath I've added the .blend file. Had to trim it a bit since it has a lot of points and was over 50mb, but the result is the same. – Gabriel Ortiz Duran Jan 29 '16 at 20:37
  • Wow, I've never seen anything like that before. There is something really really messed up about the normals on that plane. I'll have to check it out on my workstation as it's running way too slow on my tablet. – PGmath Jan 29 '16 at 21:10

1 Answers1

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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.)

Leon Cheung
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