raysSDF: Radial Ray Pattern Generator

Angular Division Pattern for Spoke and Star Designs

The raysSDF function creates radial ray patterns by dividing polar coordinates into equal angular segments. This primitive generates spoke-like patterns radiating from a center point, useful for creating star bursts, wheel spokes, and radial navigation interfaces.

Mathematical Foundation

The ray pattern is generated through polar coordinate transformation and angular division:

$$\theta = \text{atan2}(p_y - 0.5, p_x - 0.5)$$

The normalized angle is divided by the number of rays and fractional part extracted:

$$\text{rays} = \text{fract}\left(\frac{\theta}{2\pi} \times N\right)$$

where $N$ is the number of rays and the result creates repeating angular segments from 0 to 1.

Function Signature

Parameter	Type	Description
st	vec2	Input texture coordinates (0-1 range)
N	int	Number of rays to generate

Implementation Demonstrations

ライブエディター

const fragment = () => Scope(() => {
      const center = vec2(0.5)
      const dist = uv.sub(center).length()
      const fadeOut = float(0.5).smoothstep(0.3, dist)
      const minBrightness = float(0).toVar()
      Loop(4, ({ i }) => {
              const rayCount = i.add(4).mul(2)
              const rayPattern = raysSDF(uv, int(rayCount))
              const threshold = i.toFloat().mul(0.15).add(0.4)
              const rays = threshold.step(rayPattern).mul(fadeOut)
              minBrightness.assign(minBrightness.max(rays.mul(i.add(1).toFloat().div(8))))
      })
      const hue = raysSDF(uv, int(16)).mul(0.3).add(0.1)
      return vec4(minBrightness.mul(vec3(1, hue, 0.8)), 1)
})