A team at Texas A&M University proposes PIKNN (Physics-Informed K-Nearest Neighbors), a training-free few-shot learning method. By constructing an eight-dimensional physically constrained feature space incorporating laser power, scan speed, layer thickness, hatch spacing, volumetric energy density, linear energy density, and material thermal diffusivity, they achieve cross-material relative density prediction across 1,579 samples from six alloys. Trained on four source alloys (1,244 samples), PIKNN achieves 58.0% accuracy on unseen Ti6Al4V (10-shot) and 52.0% accuracy on CuCrZr (1-shot), outperforming supervised baselines (Prototypical Networks, SVM) by up to 18.3%. Ablation studies confirm that physically derived features such as energy density play a critical role, with explicit physical encoding capturing cross-material transferable structures that data-driven learned embeddings cannot express.