We propose a three-step participatory design cycle for the early urban design phase that can be integrated into the digital design chain. Step one involves a visualization method that is implemented as an interactive card-based interview technique for the collaborative requirement specification of urban designs. In step two these specifications are a) translated into simplified GIS data and then b) implemented into a grammar-based system together with the corresponding design regulations. The final outcome is a generative and iterative urban model, which includes buildings, building blocks, transportation networks and open spaces that visually communicates spatial impacts of urban design proposals.