small performance improvements

src/main/java/eu/jonahbauer/raytracing/math/Ray.java

@@ -12,9 +12,9 @@ public record Ray(@NotNull Vec3 origin, @NotNull Vec3 direction) {
 
     public @NotNull Vec3 at(double t) {
         return new Vec3(
-                origin().x() + t * direction.x(),
-                origin().y() + t * direction.y(),
-                origin().z() + t * direction.z()
+                Math.fma(t, direction.x(), origin.x()),
+                Math.fma(t, direction.y(), origin.y()),
+                Math.fma(t, direction.z(), origin.z())
         );
     }
 

src/main/java/eu/jonahbauer/raytracing/math/Vec3.java

@@ -23,15 +23,20 @@ public record Vec3(double x, double y, double z) {
 
     public static @NotNull Vec3 random(@NotNull RandomGenerator random, boolean unit) {
         var vec = new Vec3(
-                2 * random.nextDouble() - 1,
-                2 * random.nextDouble() - 1,
-                2 * random.nextDouble() - 1
+                Math.fma(2, random.nextDouble(), -1),
+                Math.fma(2, random.nextDouble(), -1),
+                Math.fma(2, random.nextDouble(), -1)
         );
         return unit ? vec.unit() : vec;
     }
 
     public static @NotNull Vec3 reflect(@NotNull Vec3 vec, @NotNull Vec3 normal) {
-        return vec.minus(normal.times(2 * normal.times(vec)));
+        var factor = - 2 * normal.times(vec);
+        return new Vec3(
+                Math.fma(factor, normal.x(), vec.x()),
+                Math.fma(factor, normal.y(), vec.y()),
+                Math.fma(factor, normal.z(), vec.z())
+        );
     }
 
     public static @NotNull Optional<Vec3> refract(@NotNull Vec3 vec, @NotNull Vec3 normal, double ri) {
@@ -56,10 +61,11 @@ public record Vec3(double x, double y, double z) {
     }
 
     public static @NotNull Vec3 average(@NotNull Vec3 current, @NotNull Vec3 next, int index) {
+        var factor = 1d / index;
         return new Vec3(
-                current.x() + (next.x() - current.x()) / index,
-                current.y() + (next.y() - current.y()) / index,
-                current.z() + (next.z() - current.z()) / index
+                Math.fma(factor, next.x() - current.x(), current.x()),
+                Math.fma(factor, next.y() - current.y(), current.y()),
+                Math.fma(factor, next.z() - current.z(), current.z())
         );
     }
 

src/main/java/eu/jonahbauer/raytracing/scene/util/HittableList.java

@@ -5,6 +5,7 @@ import eu.jonahbauer.raytracing.math.Ray;
 import eu.jonahbauer.raytracing.scene.Hittable;
 import org.jetbrains.annotations.NotNull;
 
+import java.util.ArrayList;
 import java.util.List;
 
 public final class HittableList extends HittableCollection {
@@ -12,7 +13,7 @@ public final class HittableList extends HittableCollection {
     private final @NotNull AABB bbox;
 
     public HittableList(@NotNull List<? extends @NotNull Hittable> objects) {
-        this.objects = List.copyOf(objects);
+        this.objects = new ArrayList<>(objects);
         this.bbox = AABB.getBoundingBox(this.objects).orElse(AABB.EMPTY);
     }