With recent expansion and advancement of 3D printing (3DP) technology, the textile and apparel industry is taking notice of its vast potential in developing an efficient and sustainable manufacturing process for customized products. Currently, many traditional apparel designers are facing challenges in digital 3D modeling wearable product. The obstacles lie in understanding the human-computer interaction (HCI) and the cognitive process for an apparel designer in 3D CAD product development. Based on research through design methodology, this case study explores ways the traditional apparel designer transfers tacit knowledge gained in the physical world to the virtual environment in 3D modeling a wearable product. Findings suggest that the designer's haptic and visual memory from traditional practice in a physical studio impact how spatial visualization skills are applied and how CAD tools are utilized in the 3D modeling process.