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Bend / Twist / Sine

The three deformers that cover the most common motion needs: curving a long shape (Bend), spiraling it around its axis (Twist), and rippling it (Sine).

Bend

Curves geometry along an axis.

Parameter Default Effect
axis Y Which axis the bend curls around
angle_deg 0 -180 to 180; total bend angle from start to end
start 0.0 Where the bend begins (0..1 along axis)
end 1.0 Where the bend ends
falloff 0.0 0 = no falloff, 1 = full ease at start and end

Common uses:

  • A flag pole + flag, where the pole stays straight (falloff = 0, start = 0.5).
  • An arched window frame (axis = Z, angle_deg = 30, start = 0).
  • A bending tree limb in a procedural scene.

Twist

Rotates geometry around an axis as a function of position along that axis.

Parameter Default Effect
axis Y Which axis the twist runs along
angle_deg 0 Total twist from start to end
start 0.0 Where twist begins
end 1.0 Where twist ends
profile linear linear / ease_in / ease_out / sine: how twist accumulates

Common uses:

  • A ribbon banner (axis = Y, angle = 90, profile = ease_out).
  • DNA-helix decoration.
  • A wrung-out cloth-like shape stacked under a Bend.

Sine

Adds a sine wave displacement along an axis.

Parameter Default Effect
axis X Which axis the wave runs along
amplitude 10 Pixels of displacement at the peak
wavelength 100 Pixels per cycle
phase_deg 0 Animatable; offset of the wave
direction Y Which axis the displacement points along
envelope none none / triangle / sin: modulate amplitude along axis

Common uses:

  • Animated flag wave (axis = X, direction = Y, animate phase).
  • Rippling water surface decoration.
  • Wing edge oscillation on a static butterfly skin.

Animating phase_deg over time at constant rate produces a traveling wave. The Aurora Clock tutorial's breathing glow could also be authored as a Sine on the glow placement's scale.

Combining Bend + Twist + Sine

The classic "flag in the wind" stack: Bend (small angle, animated) + Sine (high amplitude, animated phase). Stack Bend first so it shapes the flag's overall droop; Sine adds the ripple on top.

For a wing-flap, Bend (large angle, animated) is usually enough on its own. Add Sine with a low amplitude and short wavelength for a feather-ruffle effect on top.

Animating

Animate > Toggle Auto Key + scrub the timeline + drag any deformer slider. The framework records a key on each frame change.

For sine animations, drag phase_deg from 0 → 360 over the desired number of frames. The Graph Editor's tangent type should be Linear (constant rate) for a steady wave; Auto Tangent for a slightly springy wave.

Layering with masks

A flag should bend only past the pole. Combine Bend with a render part mask:

  1. Vertex-select the "after the pole" portion of the flag.
  2. Mesh > Render Part Mask > From Vertex Selection.
  3. Add the Bend deformer; it respects the mask automatically.

Performance

All three deformers are leaves on the GPU compute path and are ~0.1 ms per 10,000 vertices. Stacking five is still under 1 ms.

See also