LerpA

LerpA is a term used in computer graphics and programming to denote a variant of linear interpolation that uses an alpha parameter A to weight two values. It is commonly used for alpha blending and compositing, where a per-element or per-channel alpha controls the influence of each source value.

For scalar values, lerpA(a, b, A) = (1 - A) * a + A * b, with A in [0,1]. For vectors or colors, the same formula applies channel-wise, so each component is blended by the corresponding alpha. In practice, A can be a scalar, a per-element array, or a texture alpha channel.

LerpA is closely related to the standard linear interpolation function lerp(a, b, t). If one sets A = t, lerpA and lerp are equivalent; the distinction in some codebases is that lerpA highlights the alpha-driven weighting and is often used when A varies across data items, such as images or surfaces.

Applications include color blending, image compositing, and animation transitions. In shaders, lerpA-like behavior can be achieved with mix(a, b, A) or a*(1-A) + b*A, depending on the language and conventions.

Implementation notes: perform blending in an appropriate color space (linear space for color channels when required). Per-pixel alpha blending is computationally lightweight, but memory access patterns and texture fetches can dominate in real-time rendering. See also lerp, mix, alpha blending, and compositing.