Function push_projected_chord 

pub fn push_projected_chord(
    mesh: &mut LineMesh<3>,
    a: Vec4,
    b: Vec4,
    color_a: [f32; 4],
    color_b: [f32; 4],
    width: f32,
    projection: &Projection<4>,
    body_pos_r3: Vec3,
    view_radius: f32,
    samples: usize,
)

Samples in the body frame, then clips before adding the world translation.