compositeSourceOver: Standard Alpha Overlay

Foreground-Background Transparency Blending

The source over composite operation performs standard alpha blending where the source layer overlays the destination with alpha-based transparency mixing.

$$\text{sourceOver} = src \times \alpha_{src} + dst \times \alpha_{dst} \times (1 - \alpha_{src})$$

ライブエディター

const fragment = () => {
      const srcAlpha = uv.y
      const dstAlpha = float(0.8)
      const srcColor = vec3(1, 0.2, 0.1)
      const dstColor = vec3(0.1, 0.3, 0.9)
      const src = vec4(srcColor, srcAlpha)
      const dst = vec4(dstColor, dstAlpha)
      return compositeSourceOverVec4(src, dst)
}