Brontekst bekijken van Slicing a 3D object to SVG

[[Category:Howto]]
One can use OpenSCAD to slice a 3D STL or an object made in OpenSCAD into SVG usable with the Lasersaur.

Or in other words, turning
[[Bestand:Sphere-on-box-example.png|220px]] into [[Bestand:Sphere-on-box-as-slices-Flat.png]].

Needed: http://www.openscad.org/ - OpenScad (free).

The typical workflow is

# Create an OpenSCAD object, or import an STL of an object into OpenScad
# Add the slicing code below
# Adjust the parameters
# Render the object
# Save the resulting object as SVG
# Open the SVG in Inkscape to check and perhaps make it a bit more efficient by moving things around and/or nesting things
# Export/upload the SVG from Inkscape to the Lasersaur

== Example of a CSG object ==

Below is an example of a hollow sphere on top of a hollow cube (''thing()'' in below code) which is sliced; and each slice is then laid out flat.

<pre>
$fn = 30; // setting the resolution to high values can seriously increase rendering time!
  
module thing() // a random object, in this case a hollow sphere on top of a hollow cube.
{
    difference() 
    {
        union() 
        {
            translate([0, 0, 5 ]) cube(10,true);
            translate([0, 0, 12]) sphere(d=20);
        }
        union() 
        {
            translate([0, 0, 5 ]) cube(8,true);
            translate([0, 0, 12]) sphere(d=18);
        }
    }
}

// change these (measurements all in mm) -------------------------------------------------------------
x_dist      = 21; // desired horizontal distance between centre lines of projected cuts
y_dist      = 20; // desired vertical distance between centre lines of projected cuts

z_min       = 0;  // smallest z-coordinate object
z_max       = 23; // biggest z-coordinate object (add 1 to be safe)
slice       = 1;  // desired distance between cuts

explode     = false; // not in mm. false does nothing, x_dist and y_dist don't matter if this is true
// stop changing here --------------------------------------------------------------------------------

// some useful numbers
slicecount = (z_max - z_min)/slice; // this be the number of slices you get
rowlength  = floor(sqrt(slicecount)) + 1; // make rows and columns of projected cuts of equal length

// business end
for(s = [0:slicecount]) 
{ 
    x = x_dist * (s % rowlength); // calculate coordinates per cut
    y = y_dist * floor(s / rowlength);
    z = z_min + s * slice; // calculate height at which the cut should be made

    translate(explode ? [-x, -y, z * 2] : [0, 0, 0]) // translation if explode==true
        projection(cut = true)        // actual cut
            translate([x, y, -z])     // -z gets the correct layer, x and y do the grid move
                thing();
}
</pre>

== Example with an STL ==

An example of an STL that is loaded from a file and then sliced. You will have to manually adjust the Z range & slice distance.

  // 30x150x20 bbx
  import("dino.stl", convexity=3); 
  
  z_min = 0;
  z_max = 30;
  x_max = 20;
  y_max = 150;
  slice = 0.5;
  
  n = floor(sqrt((z_max - z_min)/slice)+1);
  for(z = [-z_max:slice:z_min]) { 
    i = (z + z_max) / slice;
    x = x_max * (i % n);
    y = Y_max * floor(i / n);
    translate([x,y,0]) {
        projection(cut=true) 
            translate([0,0,z]) thing();
    };
  };