We can create Polymorphism using enums

src/geometry.rs

@@ -33,6 +33,22 @@ pub enum Geometry {
     Line(Line),
 }
 
+impl Geometry {
+    pub fn greet(&self) {
+        match self {
+            Geometry::Sphere(_) => {
+                println!("Sphere!");
+            }
+            Geometry::Line(_) => {
+                println!("Line!");
+            }
+            Geometry::Plane(_) => {
+                println!("Plane!");
+            }
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/main.rs

@@ -61,6 +61,9 @@ impl RenderableGeometry {
 fn main() {
     let tex = Rc::new(Texture::load_texture());
 
+    let sphere = Geometry::Sphere(Sphere::new(Point3::new(0.0, 0.0, 0.0), 1.0));
+    sphere.greet();
+
     let geo1 = RenderableGeometry::new(
         Mat4x4::ident(),
         Geometry::Sphere(Sphere::new(Point3::new(0.0, 0.0, 0.0), 1.0)),