diff --git a/src/facet.jl b/src/facet.jl
index 1bd4995c..406cb18f 100644
--- a/src/facet.jl
+++ b/src/facet.jl
@@ -4,14 +4,14 @@
 # #                      Face properties
 # ################################################################
 
-face_center(vs) = face_center(vs...)
-face_center(v1, v2, v3) = (v1 + v2 + v3) / 3
+face_center(vs::StaticVector{3, <:StaticVector{3}}) = face_center(vs...)
+face_center(v1::StaticVector{3}, v2::StaticVector{3}, v3::StaticVector{3}) = (v1 + v2 + v3) / 3
 
-face_normal(vs) = face_normal(vs...)
-face_normal(v1, v2, v3) = normalize((v2 - v1) × (v3 - v2)) 
+face_normal(vs::StaticVector{3, <:StaticVector{3}}) = face_normal(vs...)
+face_normal(v1::StaticVector{3}, v2::StaticVector{3}, v3::StaticVector{3}) = normalize((v2 - v1) × (v3 - v2))
 
-face_area(vs) = face_area(vs...)
-face_area(v1, v2, v3) = norm((v2 - v1) × (v3 - v2)) / 2
+face_area(vs::StaticVector{3, <:StaticVector{3}}) = face_area(vs...)
+face_area(v1::StaticVector{3}, v2::StaticVector{3}, v3::StaticVector{3}) = norm((v2 - v1) × (v3 - v2)) / 2
 
 
 ################################################################
@@ -54,7 +54,7 @@ end
 Intersection detection between ray R and triangle ABC.
 Note that the starting point of the ray is the origin (0, 0, 0).
 """
-function raycast(A, B, C, R)
+function raycast(A::StaticVector{3}, B::StaticVector{3}, C::StaticVector{3}, R::StaticVector{3})
     E1 = B - A
     E2 = C - A
     T  = - A
@@ -77,7 +77,7 @@ end
 Intersection detection between ray R and triangle ABC.
 Use when the starting point of the ray is an arbitrary point `O`.
 """
-raycast(A, B, C, R, O) = raycast(A - O, B - O, C - O, R)
+raycast(A::StaticVector{3}, B::StaticVector{3}, C::StaticVector{3}, R::StaticVector{3}, O::StaticVector{3}) = raycast(A - O, B - O, C - O, R)
 
 
 """
diff --git a/src/roughness.jl b/src/roughness.jl
index 003e98c2..d022b7d8 100644
--- a/src/roughness.jl
+++ b/src/roughness.jl
@@ -13,7 +13,7 @@ Return the curvature radius of a concave spherical segment.
 - `r`: Crater radius
 - `h`: Crater depth
 """
-crater_curvature_radius(r, h) = (r^2 + h^2) / 2h
+crater_curvature_radius(r::Real, h::Real) = (r^2 + h^2) / 2h
 
 """
     concave_spherical_segment(r, h, xc, yc, x, y) -> z
@@ -28,7 +28,7 @@ Return the z-coordinate of a concave spherical segment.
 - `x` : x-coordinate where to calculate z
 - `y` : y-coordinate where to calculate z
 """
-function concave_spherical_segment(r, h, xc, yc, x, y)
+function concave_spherical_segment(r::Real, h::Real, xc::Real, yc::Real, x::Real, y::Real)
     d² = (x - xc)^2 + (y - yc)^2
     d = √d²  # Distance from the crater center
 
@@ -54,7 +54,7 @@ Return (x, y, z) grid of a concave spherical segment.
 - `xc`: x-coordinate of crater center
 - `yc`: y-coordinate of crater center
 """
-function concave_spherical_segment(r, h; Nx=2^5, Ny=2^5, xc=0.5, yc=0.5)
+function concave_spherical_segment(r::Real, h::Real; Nx::Integer=2^5, Ny::Integer=2^5, xc::Real=0.5, yc::Real=0.5)
     xs = LinRange(0, 1, Nx + 1)
     ys = LinRange(0, 1, Ny + 1)
     zs = [concave_spherical_segment(r, h, xc, yc, x, y) for x in xs, y in ys]