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//! See [Mesh](crate::mesh::Mesh).

use crate::mesh::*;

/// # Vertex measures
impl Mesh {
    /// Returns the vertex position.
    pub fn vertex_position(&self, vertex_id: VertexID) -> Vec3 {
        self.position(vertex_id)
    }

    /// Returns the normal of the vertex given as the average of the normals of the neighbouring faces.
    pub fn vertex_normal(&self, vertex_id: VertexID) -> Vec3 {
        let mut normal = Vec3::zero();
        for halfedge_id in self.vertex_halfedge_iter(vertex_id) {
            if let Some(face_id) = self.walker_from_halfedge(halfedge_id).face_id() {
                normal += self.face_normal(face_id)
            }
        }
        normal.normalize()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_vertex_normal() {
        let mesh = crate::test_utility::subdivided_triangle();
        let computed_normal = mesh.vertex_normal(unsafe { VertexID::new(0) });
        assert_eq!(0.0, computed_normal.x);
        assert_eq!(0.0, computed_normal.y);
        assert_eq!(1.0, computed_normal.z);
    }
}