Added a short OpenSCAD description to aid in the creation of simple m…

…odifier meshes that describe a change every N layers

utils/modifier_helpers/solid_layers.scad

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+// Used to generate a modifier mesh to do something every few layers. 
+// Load into OpenSCAD, tweak the variables below, export as STL and load as 
+// a modifier mesh. Then change settings for the modifier mesh.
+
+// Written by Joseph Lenox; in public domain.
+
+layer_height = 0.3; // set to layer height in slic3r for "best" results.
+number_of_solid_layers = 2;
+N = 4; // N > number_of_solid_layers or else the whole thing will be solid
+model_height = 300.0;
+model_width = 300.0; // these two should be at least as big as the model 
+model_depth = 300.0; // but bigger isn't a problem
+initial_offset=0; // don't generate below this
+
+position_on_bed=[0,0,0]; // in case you need to move it around
+
+// don't touch below unless you know what you are doing.
+simple_layers = round(model_height/0.3);
+translate(position_on_bed)
+  for (i = [initial_offset:N:simple_layers]) {
+    translate([0,0,i*layer_height])
+      translate([0,0,(layer_height*number_of_solid_layers)/2])
+      cube([model_width,model_depth,layer_height*number_of_solid_layers], center=true);
+  }