add metal

src/main/java/eu/jonahbauer/raytracing/Main.java

@@ -1,6 +1,7 @@
 package eu.jonahbauer.raytracing;
 
 import eu.jonahbauer.raytracing.material.LambertianMaterial;
+import eu.jonahbauer.raytracing.material.MetallicMaterial;
 import eu.jonahbauer.raytracing.render.Camera;
 import eu.jonahbauer.raytracing.render.Color;
 import eu.jonahbauer.raytracing.render.ImageFormat;
@@ -13,8 +14,10 @@ import java.nio.file.Path;
 public class Main {
     public static void main(String[] args) throws IOException {
         var scene = new Scene(
-                new Sphere(0, 0, 1, 0.5, new LambertianMaterial(Color.RED)),
-                new Sphere(0, -100.5, 1, 100, new LambertianMaterial(Color.BLUE))
+                new Sphere(0, -100.5, 1, 100, new LambertianMaterial(new Color(0.8, 0.8, 0.0))),
+                new Sphere(0, 0, 1.2, 0.5, new LambertianMaterial(new Color(0.1, 0.2, 0.5))),
+                new Sphere(-1, 0, 1, 0.5, new MetallicMaterial(new Color(0.8, 0.8, 0.8))),
+                new Sphere(1, 0, 1, 0.5, new MetallicMaterial(new Color(0.8, 0.6, 0.2)))
         );
         var camera = new Camera(512, 2, 16 / 9d);
 

src/main/java/eu/jonahbauer/raytracing/material/MetallicMaterial.java

@@ -0,0 +1,23 @@
+package eu.jonahbauer.raytracing.material;
+
+import eu.jonahbauer.raytracing.math.Ray;
+import eu.jonahbauer.raytracing.render.Color;
+import eu.jonahbauer.raytracing.scene.HitResult;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.Objects;
+import java.util.Optional;
+
+public record MetallicMaterial(@NotNull Color albedo) implements Material {
+    public MetallicMaterial {
+        Objects.requireNonNull(albedo, "albedo");
+    }
+
+    @Override
+    public @NotNull Optional<ScatterResult> scatter(@NotNull Ray ray, @NotNull HitResult hit) {
+        var direction = ray.direction();
+        var normal = hit.normal();
+        var newDirection = direction.minus(normal.times(2 * normal.times(direction)));
+        return Optional.of(new ScatterResult(new Ray(hit.position(), newDirection), albedo));
+    }
+}