OpenSCAD::render()

render()
Adding render() before a code block forces OpenSCAD to render and cache the mesh produced by that code, making each successive render much faster.

An Example
The following OpenSCAD program was a dissection of

member Emmett Lalish's file Rhombic Dodecahedra Chain.

Starting with the following shapes where L= the height of the module and in this case 40:

    translate ([-60,0,0])rotate([0,0,45])cube(L*[1,1,2],center=true);
    translate ([0,0,0])rotate([0,45,0])cube(L*[1,2,1],center=true);
    translate ([70,0,0])rotate([45,0,0])cube(L*[2,1,1],center=true);

Combine each shape by using intersection(). The shape created will be just where the three shapes intersect:

intersection(){
    rotate([0,0,45])cube(L*[1/s,1/s,2],center=true);
    rotate([0,45,0])cube(L*[s,2,s],center=true);
    rotate([45,0,0])cube(L*[2,s,s],center=true);
}

Now you want to create another form using these shapes.

Here L is still 40, and s=fraction of the face to hollow/2+0.5

translate([-70,0,0])rotate([0,0,45])cube(L*[1/s,1/s,2],center=true);
translate([20,0,0])rotate([0,45,0])cube(L*[s,2,s],center=true);
translate([100,0,0])rotate([45,0,0])cube(L*[2,s,s],center=true);

Combine each shape again by using intersection(). The shape created will be just where the three shapes intersect:

intersection(){
    rotate([0,0,45])cube(L*[1/s,1/s,2],center=true);
    rotate([0,45,0])cube(L*[s,2,s],center=true);
    rotate([45,0,0])cube(L*[2,s,s],center=true);
}

You should now have two shapes:

The next thing to do is create a boolean difference of the second form from the first form:
The next step is the continue differencing from the initial form. This time you will rotate the second form 90° on the X axis:
The last step is to create another difference from the initial form. This time rotate the second form 90° on the Y axis:
If you wanted to see how the form falls on the platform, you could add a cube:
```
%cube([220,140,1],center=true);
```
Rotating the form by 45° on the X axis and 90° on the Z axis will straighten the form:
```
rotate([45,0,90])
```
Now to raise the form to sit on the platform:
```
rotate([45,0,90])
```
Surround the code with
```
render(){

}
```

Then put it in a module:

module openRhom(){
   render(){
       translate([0,0,L/2])
       rotate([45,0,90])
       difference(){
          firstShape();
          secondShape();
          rotate([90,0,0])secondShape();
          rotate([0,90,0])secondShape();
       }
    }
}

Now you can quickly preview chains. Here set a variable d to be the 16.5:

chain(20);
module chain(n){
    translate([-(n-1)*1*d+d,0,0])
    for(i=[1:n]){
	    translate([(i-1)*2*d,0,0])
	    openRhom();
    }    
}

Challenge: