Hello!

I have some questions and I would like a solution.

I'm still learning openscade for now. However, I noticed that, considering the difference between two primitives, the preview does not appear. I can only see the result when I render it.
(Linux Mint 21 Cinnamon
Pentium© Dual-Core CPU E5400 @ 2.70GHz × 2
Intel Corporation 4 Series Chipset Integrated Graphics Controller 3.7GB)

Can it be solved with some setting so that the preview is also visible?


The other question must have been somewhere. Sorry!
I am importing a binary stl. It displays and renders nicely.
Then I would multiply this imported file with a for loop. The preview shows exactly what I want, but the rendering does not execute.

module head(){
  union(){

  difference(){
    translate([0, 0, 0]) {
      scale([1, 1, 1.7])
        import("horse3.stl");
    }


  $fn=32;
  // eye1
    translate([5, 11, 73]){
      sphere(2.5);
    } 
    
 // eye2
    translate([5, -3, 55]){
      sphere(2.5);
    } 
 } //difference
 } //union
} //module head

 for (i=[0 : 120 : 360]) {
    rotate([0, 0, i])
      translate([5,5,0])
        head();
  }

Throw a CGAL error (CGAL error in CGALUtils::applyUnion3D: CGAL ERROR: precondition violation! Expr: ! _is_valid (_succ2_P) || comp_f (node1_P->object, _succ2_P->object) != LARGER File: /usr/include/CGAL /Multiset.h Line: 2344 ), 

and a warning (No top level geometry to render).

And of course nothing appears.

Why? Why is rendering fine with plain import and not working with loop?
Is it possible to put the result of the cycle in a variable and display it?

I have another problem with this job.
The preview isn't really good though.
The attached pictures shows that the surface is transparent. I checked and corrected the original file with FReecad.

Thanks, convexity solved the preview. :)

- ”try this”
As you can see in the picture, the cube appears in the preview, but the render does not display the cube either. The CGAL error and "no renderable surface" remained.

• variable

I mean, something like this:  $Head= cycle;

I tried this and it didn't work either.

module heads(){

 for (i=[0 : 120 : 360]) {

    rotate([0, 0, i])

      translate([5,5,0])

        //scale([1,1, 1.3])

        head();  } // for i
}

heads();