diff --git a/src/sconvcol.h b/src/sconvcol.h
index 883706c..5451b6b 100644
--- a/src/sconvcol.h
+++ b/src/sconvcol.h
@@ -9,7 +9,7 @@ extern "C" {
 #include <stdbool.h>
 
 #include "vectorial/simd4x4f.h"
-8
+
 inline bool sch_simd4f_equal(simd4f a, simd4f b) {
   return (simd4f_get_x(simd4f_length4_squared(simd4f_sub(a, b))) == 0.f);
 }
@@ -101,9 +101,9 @@ SchHullResult sch_builder_create_hull(sch_hull_builder* builder, sch_hull* out_h
 // Calculations
 //
 
-float sch_plane_distance(sch_plane* plane, simd4f* v);
+float sch_plane_distance(const sch_plane* plane, const simd4f* v);
 
-void sch_edge_get_dir(sch_edge* edge, simd4f* dir);
+void sch_edge_get_dir(const sch_edge* edge, simd4f* out_dir);
 
 void sch_hull_free_memory (sch_hull* hull);
 
@@ -127,7 +127,7 @@ void sch_create_face(int num_vert, simd4f* vertices, sch_face* out_face);
 
 #ifdef SCONVCOL_IMPLEMENTATION
 
-float sch_plane_distance(sch_plane* plane, simd4f* v) {
+float sch_plane_distance(const sch_plane* plane, const simd4f* v) {
   return simd4f_dot3_scalar(simd4f_sub(*v, plane->p), plane->n);
 }
 
@@ -157,7 +157,7 @@ void sch_create_face(int num_vert, simd4f* vertices, sch_face* out_face) {
   out_face->edge = &f_edges[0];
 }
 
-void sch_edge_get_dir(sch_edge* edge, simd4f* out_dir) {
+void sch_edge_get_dir(const sch_edge* edge, simd4f* out_dir) {
   *out_dir = simd4f_sub(edge->next->vert->p, edge->vert->p);
   float recip_len = 1.f / sqrtf(simd4f_dot3_scalar(*out_dir, *out_dir));
   *out_dir = simd4f_mul(*out_dir, simd4f_splat(recip_len));