Model notes & references
Seed n sits at radius r = c√n and angle θ = n × α (Vogel's construction). The golden angle is 360° × (1 − 1/φ) ≈ 137.5078°, with φ = (1 + √5)/2.
Spacing CV is the standard deviation of nearest-neighbour distances divided by their mean, for up to 400 evenly sampled seeds against the whole head; lower means more even spacing. Spiral guides join seeds whose index offsets are continued-fraction denominators of α/360° that are nearest neighbours at the rim of the visible head. They are mathematical guides, not measurements of real plants; real flower heads vary and do not always show Fibonacci counts.
- H. Vogel (1979), A better way to construct the sunflower head, Mathematical Biosciences 44, 179–189. doi:10.1016/0025-5564(79)90080-4
- J. Swinton, E. Ochu et al. (2016), Novel Fibonacci and non-Fibonacci structure in the sunflower, Royal Society Open Science 3, 160091. doi:10.1098/rsos.160091
Original code and procedural art by explainer tools.