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openscad

Result is ok at preview, but empty after rendering

I want to cut this hemisphere:

enter image description here

my code is:

difference() {
import("../kupol.stl");
translate([-150,-1,-1]) cube(500);
}

at preview result is ok:

enter image description here

but after rendering (F6 key) I received an empty object:

enter image description here

Rendering was finished without any errors:

Compiling design (CSG Tree generation)...
Rendering Polygon Mesh using CGAL...
Geometries in cache: 15
Geometry cache size in bytes: 3178728
CGAL Polyhedrons in cache: 12
CGAL cache size in bytes: 0
Total rendering time: 0 hours, 0 minutes, 0 seconds
Rendering finished.

I'm using OpenSCAD version 2015.03-2 at Windows 7 64bit machine. Here is detailed information about my build and here is stl with hemisphere which I need to cut.

What am I doing wrong?

Solution

  • The STL has probably some problems. Make sure it's manifold (which can be checked with most mesh editors, e.g. MeshLab, Blender, Netfabb).

    Also have a look at the FAQ which explains an additional issue that can cause OpenSCAD to have problems with the STL (Zero-Faces = Triangles that have no area).