In programmatic CAD (PCAD), 3D shapes are generally modelled either by position-based composition of simpler shapes, or by direct generation via path-based techniques (e.g., extrusions, sweeps, revolves). While state-of-the-art PCAD tools effectively support position-based modelling, they lack expressive mechanisms for path-based modelling. As a result, shapes that are naturally formed by sweeping a 2D path into a 3D shape are difficult to model and use in these tools. This paper introduces TurtleTalk, a PCAD language that offers rich support for constructing path-based shapes and the composition of path-based and primitive shapes. TurtleTalk is an extension of PrintTalk, a PCAD language featuring constraints for composing constituent shapes into complex 3D models. TurtleTalk takes inspiration from turtle graphics for constructing paths using imperative instructions and uniquely integrates constraints to enable the declarative expression of path properties. Our evaluation shows that combining imperative instructions and declarative constraints facilitates the design of path-based shapes by reducing the need for complex manual calculations, while also enhancing their composability and reusability.

We present PrintTalk, a DSL to "program" 3D objects, called "gadgets". PrintTalk also features "topologies", which are predefined spacial arrangements of gadgets. Gadgets are composed by executing a gadget script (possibly consisting of subscripts) that 'draws' the gadget in the 3D scene. However, executing the script also returns a number of constraint variables. These variables can be constrained inside the gadget and can also be bound outside the gadget in order to constrain the produced gadgets after the facts. This is the essence of the gadget composition mechanism of PrintTalk.