Move lerp/cubic to alnumeric.h

1 files changed, 13 insertions, 0 deletions

diff --git a/common/alnumeric.h b/common/alnumeric.h
index d3d0edfd..8d13f9bf 100644
--- a/common/alnumeric.h
+++ b/common/alnumeric.h
@@ -67,6 +67,19 @@ constexpr inline size_t clampz(size_t val, size_t min, size_t max) noexcept
 { return minz(max, maxz(min, val)); }
 
 
+constexpr inline float lerp(float val1, float val2, float mu) noexcept
+{ return val1 + (val2-val1)*mu; }
+constexpr inline float cubic(float val1, float val2, float val3, float val4, float mu) noexcept
+{
+    const float mu2{mu*mu}, mu3{mu2*mu};
+    const float a0{-0.5f*mu3 +       mu2 + -0.5f*mu};
+    const float a1{ 1.5f*mu3 + -2.5f*mu2            + 1.0f};
+    const float a2{-1.5f*mu3 +  2.0f*mu2 +  0.5f*mu};
+    const float a3{ 0.5f*mu3 + -0.5f*mu2};
+    return val1*a0 + val2*a1 + val3*a2 + val4*a3;
+}
+
+
 /** Find the next power-of-2 for non-power-of-2 numbers. */
 inline uint32_t NextPowerOf2(uint32_t value) noexcept
 {