relativity.scad OpenSCAD Library

The relativity.scad library introduces a set of modules designed to replace standard OpenSCAD primitives. These new primitives allow objects and their children to align and size themselves relative to their parent's dimensions using the $parent_size variable.

Instead of manually calculating offsets using hardcoded dimensions (e.g., translate([cube_h/2, 0, 0])), you can use anchor parameters and the align() module to position objects based on their own geometry and the geometry of their parents.

// Standard OpenSCAD approach (manual calculation)
cube_h=10;
cylinder_d=7;
translate([0,0,cube_h/2]){
    cube(cube_h, center=true);
    translate([cube_h/2 + cylinder_d/2,0,0])
    cylinder(d=cylinder_d, h=cube_h, center=true);
}

// relativity.scad approach (relative positioning)
box(10, anchor=[0,0,-1])
align([1,0,0])
rod(d=7, h=$parent_size.z);

The library implements a pattern similar to CSS for HTML, allowing you to separate the definition of a model (content) from how it is rendered (presentation).

• Content Layer: Define all parts of a project and how they interact (e.g., using attachment points).
• Presentation Layer: Use CSG operations like show, hide, or attach to isolate specific parts for printing or to assemble components like Lego blocks.

The library provides several modules to perform Constructive Solid Geometry (CSG) operations based on object classes. These allow for complex pattern generation and visibility control.

Module | Description
--------- --------------
mirrored | form bilaterally symmetric objects using the `mirror()` function 
rotated | form radially symmetric objects by repeated calls to `rotate()` 
translated | form repeating patterns by repeated calls to `translate() `
hulled | performs `hull` between objects of a given class
intersected | performs `difference` between objects of a given class
differed | performs `difference` between one class of objects and another
show | renders only the specified class 
hide | renders everything but the specified class 
attach | attaches child to the parent at an attachment point of a given class