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blendSubtract: Additive Threshold Clamping Mode

Unity-Based Threshold Function for High-Luminance Extraction​

The subtract blend mode applies an additive threshold operation where color values persist only when the combined luminance exceeds unity. This creates high-contrast selections based on luminance accumulation.

The mathematical definition uses threshold clamping:

subtract(base,blend)=max⁡(base+blend−1,0)\text{subtract}(base, blend) = \max(base + blend - 1, 0)

Values below the unity threshold are eliminated, while excess luminance above 1.0 creates the final result. This produces stark binary separations between preserved and eliminated regions.

Live Editor
const fragment = () => {
      const baseGrad = vec3(uv.x, uv.x.mul(0.7), uv.x.mul(0.4))
      const blendGrad = vec3(uv.y.mul(0.6), uv.y, uv.y.mul(0.8))
      const subtracted = blendSubtractVec3(baseGrad, blendGrad)
      const amplified = subtracted.mul(4)
      return vec4(amplified, 1)
}