Industrial LSAM systems typically extrude at constant layer height and width to simplify toolpath generation and quality control. Uniform extrusion limits the ability to locally vary thermal, structural, and material-efficiency performance, constraining both design and function. This work presents a framework coupling distance fields with performance-driven field functions to govern spatially variable extrusion in architectural-scale 3D printing [1]. A distance field defines the medial axis of the target geometry; a second field maps thermal or structural demands to a desired extrusion width at each toolpath location. The realized width at any point is twice the lesser of the boundary distance or the performance-driven target, ensuring the deposited material does not exceed the design boundary. A single continuous toolpath thus produces graded material distribution, thicker where greater thermal mass or load bearing is required, thinner where material can be saved, without infill or multiple shells. Extrusion width is controlled by modulating robot traverse speed or extruder screw speed, standard procedures within the LSAM field [2]. Representing feeds and speeds as dimensionless ratios allows identical machine code to run across material batches with different rheological properties, a practical necessity for viscous feedstocks like earth or ready-mix mortar that already require some human-in-the loop control. Because the performance field is independent of the geometric field, the method generalizes across design objectives. A case study applies the framework to a hybrid 3D printed earth wall designed to meet California building code. Extrusion width varies to balance thermal mass and insulation for the local climate while the printed geometry serves as lost formwork for reinforced concrete. Compared to conventional geometry-based space-filling toolpaths, the method improves material efficiency without reducing print stability. This contribution shifts LSAM toolpath design from uniform geometry-driven deposition toward multi-field, performance-driven fabrication using locally sourced materials.