Mind maps simply document all thoughts surrounding a central subject. I use them often to help reveal unseen connections and generate concept development directions.
Initial concept sketching is fast and comprehensive, exploring a wide range of ideas.
Development sketches help refine initial concepts.
Hand rendering offers a faster alternative to 3D computer modeling for visual assessment.
Sketch models are essential to developing form, proportion and function. This model was made using a 3D printer but often sketch models made by hand from common scrap materials are just as effective.
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Concept

Research, mind maps, sketching, form studies and sketch modeling are the concept development tools I use most often.