Readd some ROyFit methods

src/NeRCA.jl

@@ -58,6 +58,7 @@ include("hits.jl")
 include("mc.jl")
 include("scanfit.jl")
 include("dumandfit.jl")
+include("royfit.jl")
 include("db.jl")
 
 end

src/royfit.jl

+mutable struct SingleDUParams
+    d::Float64
+    t::Float64
+    z::Float64
+    dz::Float64
+    t₀::Float64
+end
+
+"""
+Returns a function which calculates the arrival time of a Cherenkov photon
+at a given position.
+"""
+function make_cherenkov_calculator(d_closest, t_closest, z_closest, dir_z, t₀; n=KM3io.Constants.INDEX_OF_REFRACTION_WATER)
+    c_ns = KM3io.Constants.c / 1e9
+    d_γ(z) = n/√(n^2 - 1) * √(d_closest^2 + (z-z_closest)^2 * (1 - dir_z^2))
+    t(z) = (t₀) + 1/c_ns * ((z - z_closest)*dir_z + (n^2 - 1)/n * d_γ(z))
+    d_γ, t
+end
+
+"""
+Returns a function which calculates the arrival time of a Cherenkov photon
+at a given position.
+"""
+function make_cherenkov_calculator(sdp::SingleDUParams; n=KM3io.Constants.INDEX_OF_REFRACTION_WATER)
+    c_ns = KM3io.Constants.c / 1e9
+    d_γ(z) = n/√(n^2 - 1) * √(sdp.d^2 + (z-sdp.z)^2 * (1 - sdp.dz^2))
+    t(z) = (sdp.t₀) + 1/c_ns * ((z - sdp.z)*sdp.dz + (n^2 - 1)/n * d_γ(z))
+    d_γ, t
+end
+
+