Drag the scene to orbit, pinch or scroll to zoom.
Use Pause / Reset at the top to freeze or restart the simulation.
The tabs at the bottom control each tropism. The ? button explains the shape dynamics.
Torture the plant by rotating the pot (Pot tab) or moving the light source (Light tab).
The stem is a 3D curve. Growth occurs along the green growth zone β when one side elongates faster than the other, the stem bends. The brown mature zone is permanently fixed.
The classic way to torture a houseplant is to rotate the pot β the stem was growing toward the window, and now gravity and light pull it a different way. Use the Pot tab to tilt and spin. You can also move the light source to the other side and watch the plant chase it. What shape can you grow?
Plants sense gravity and grow against it (shoots) or toward it (roots). Negative sensitivity = shoot-like, grows upward. Positive = root-like, grows downward.
Add a point light source and the plant bends toward it. Sensitivity follows Stevens' power law β response grows non-linearly with signal strength. Drag the β sphere to reposition it; use the height slider to move it up and down.
The plant senses its own curvature and resists over-bending β like an internal straightening drive. Without it the stem would spiral without limit. The balance number B = Ξ²Β·L_gz / Ξ³ describes whether autotropism dominates (Bβͺ1, smooth straightening) or the tropism response overshoots (Bβ«1, oscillatory tip).
Many plant shoots spontaneously spiral their growing tip in circles β driven by an internal oscillator, not any external signal. This helps climbing plants search for supports. You can tune the amplitude and period.
The Ξ tab overlays arrows showing the differential growth direction at each cross-section of the growth zone β the direction in which one side of the stem elongates faster than the other. Each arrow shows one stimulus (gravity, light, autotropism, or circumnutations), and the Total arrow is their vector sum. Arrow length is proportional to magnitude.