add "lorp" (log interpolation) function

inmath/interpolate.d

@@ -9,7 +9,7 @@ module inmath.interpolate;
 private {
     import inmath.linalg : Vector, dot, vec2, vec3, vec4, quat;
     import inmath.util : isVector, isQuaternion;
-    import inmath.math : almostEqual, acos, sin, sqrt, clamp, PI;
+    import inmath.math : almostEqual, acos, sin, sqrt, clamp, PI, exp, log;
     import std.conv : to;
 }
 
@@ -20,6 +20,12 @@ T lerp(T)(T a, T b, float t) {
     return a * (1 - t) + b * t;
 }
 
+/// Logarithmically interpolates between `a` and `b`, using scalar `t` from 0..1
+/// Also known as eerp
+T lorp(T)(T a, T b, float t) {
+    return a * exp( t * log(b / a));
+}
+
 /// Linearly interpolates between to vectors or quaternions.
 T slerp(T)(T a, T b, float t) if(isVector!T || isQuaternion!T) {
     static if(isVector!T) {