added important comment for `feature` field in Intersection struct
@@ -68,6 +68,13 @@ pub struct Intersection {
/// Additional data that contains a kind of the feature with which
/// intersection was detected as well as its index.
+ ///
+ /// # Important notes.
+ ///
+ /// FeatureId::Face might have index that is greater than amount of triangles in
+ /// a triangle mesh, this means that intersection was detected from "back" side of
+ /// a face. To "fix" that index, simply subtract amount of triangles of a triangle
+ /// mesh from the value.
pub feature: FeatureId,
/// Distance from the ray origin.
