# Function: radiate()

[**lifecycle-kit**](https://jonbogaty.com/lifecycle-kit/api/readme/index.md)

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[lifecycle-kit](https://jonbogaty.com/lifecycle-kit/api/readme/index.md) / [forms](https://jonbogaty.com/lifecycle-kit/api/forms/readme/index.md) / radiate


# Function: radiate() {#function-radiate}


> **radiate**(`unit`, `params`): [`Path`](https://jonbogaty.com/lifecycle-kit/api/forms/interfaces/path/index.md)

Defined in: [forms/rules/radiate.ts:54](https://github.com/jbcom/lifecycle-kit/blob/074e4e7b8038d3e2de9eb44c4b5b5aee0ef02b48/src/forms/rules/radiate.ts#L54)

Place `count` copies of a unit appendage radially around a centre.

The generalisation of `pair` from two sides to N: a starfish's arms, a sea
anemone's tentacle ring, or a jellyfish's tentacles. `spreadTurns` covers both:
1.0 for the anemone's full ring, less than 1.0 for tentacles that trail
from the underside of a bell rather than surrounding it.

The unit is authored pointing along +x from the centre; each copy is
rotated to its position on the ring and translated out to `center`. Copies
are `count` evenly spaced slots covering `spreadTurns`, always dividing by
`count` and never by `count - 1`.

An earlier version divided by `count - 1` below a full turn, so the last
copy landed exactly at the far end of the spread, and switched to dividing
by `count` at `spreadTurns = 1` so a ring's first and last copy did not
coincide. That is a genuine cliff at spreadTurns = 1 — sweeping through it
jumps the last copy's angle discontinuously — and the continuity assay in
`radiate.test.ts` exists precisely to catch this class of bug. One formula
for every spread is what removes it: a partial arc's last copy sits one
slot short of the spread's far edge rather than exactly on it, which is a
real behaviour change from the inclusive-endpoint version, not a
simplification of the same one.


## Parameters {#parameters}



### unit {#unit}


[`Path`](https://jonbogaty.com/lifecycle-kit/api/forms/interfaces/path/index.md)


### params {#params}


[`RadiateParams`](https://jonbogaty.com/lifecycle-kit/api/forms/interfaces/radiateparams/index.md)


## Returns {#returns}


[`Path`](https://jonbogaty.com/lifecycle-kit/api/forms/interfaces/path/index.md)