prevent StackOverflowError in SimpleRenderer

src/main/java/eu/jonahbauer/raytracing/render/renderer/SimpleRenderer.java

@@ -86,20 +86,28 @@ public final class SimpleRenderer implements Renderer {
     }
 
     private @NotNull Color getColor0(@NotNull Scene scene, @NotNull Ray ray, int depth) {
-        if (depth <= 0) return Color.BLACK;
+        var color = Color.BLACK;
+        var attenuation = Color.WHITE;
+
+        while (depth-- > 0) {
+            var optional = scene.hit(ray, new Range(0.001, Double.POSITIVE_INFINITY));
+            if (optional.isEmpty()) {
+                color = Color.add(color, Color.multiply(attenuation, scene.getBackgroundColor(ray)));
+                break;
+            }
 
-        var optional = scene.hit(ray, new Range(0.001, Double.POSITIVE_INFINITY));
-        if (optional.isPresent()) {
             var hit = optional.get();
             var material = hit.material();
             var emitted = material.emitted(hit);
-            return material.scatter(ray, hit)
-                    .map(scatter -> Color.multiply(scatter.attenuation(), getColor0(scene, scatter.ray(), depth - 1)))
-                    .map(color -> Color.add(color, emitted))
-                    .orElse(emitted);
-        } else {
-            return scene.getBackgroundColor(ray);
+            var scatter = material.scatter(ray, hit);
+            color = Color.add(color, Color.multiply(attenuation, emitted));
+
+            if (scatter.isEmpty()) break;
+            attenuation = Color.multiply(attenuation, scatter.get().attenuation());
+            ray = scatter.get().ray();
         }
+
+        return color;
     }
 
     /**