add RandomGenerator parameter to Hittable#hit

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

@@ -128,7 +128,7 @@ public final class SimpleRenderer implements Renderer {
         var attenuation = white;
 
         while (depth-- > 0) {
-            var optional = scene.hit(ray);
+            var optional = scene.hit(ray, random);
             if (optional.isEmpty()) {
                 var background = scene.getBackgroundColor(ray);
                 color = SampledSpectrum.fma(attenuation, background, color);

src/main/java/eu/jonahbauer/raytracing/scene/Hittable.java

@@ -9,15 +9,16 @@ import eu.jonahbauer.raytracing.scene.transform.Translate;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.Optional;
+import java.util.random.RandomGenerator;
 
 public interface Hittable {
     @NotNull Range FORWARD = new Range(0.001, Double.POSITIVE_INFINITY);
 
     /**
-     * @see #hit(Ray, Range)
+     * @see #hit(Ray, Range, RandomGenerator)
      */
-    default @NotNull Optional<HitResult> hit(@NotNull Ray ray) {
+    default @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull RandomGenerator random) {
-        return hit(ray, FORWARD);
+        return hit(ray, FORWARD, random);
     }
 
     /**
@@ -31,7 +32,7 @@ public interface Hittable {
      * @return the result of the hit test, containing (among others) the value {@code t} such that {@code ray.at(t)} is
      *         a point on {@code this} hittable
      */
-    @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range);
+    @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range, @NotNull RandomGenerator random);
 
     /**
      * {@return the axis-aligned bounding box of this hittable}

src/main/java/eu/jonahbauer/raytracing/scene/Scene.java

@@ -12,6 +12,7 @@ import org.jetbrains.annotations.Nullable;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
+import java.util.random.RandomGenerator;
 
 public final class Scene extends HittableCollection {
     private final @NotNull HittableCollection objects;
@@ -42,8 +43,8 @@ public final class Scene extends HittableCollection {
     }
 
     @Override
-    public void hit(@NotNull Ray ray, @NotNull State state) {
+    public void hit(@NotNull Ray ray, @NotNull State state, @NotNull RandomGenerator random) {
-        objects.hit(ray, state);
+        objects.hit(ray, state, random);
     }
 
     @Override

src/main/java/eu/jonahbauer/raytracing/scene/hittable2d/Hittable2D.java

@@ -7,9 +7,11 @@ import eu.jonahbauer.raytracing.render.material.Material;
 import eu.jonahbauer.raytracing.scene.HitResult;
 import eu.jonahbauer.raytracing.scene.Hittable;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.Objects;
 import java.util.Optional;
+import java.util.random.RandomGenerator;
 
 public abstract class Hittable2D implements Hittable {
     protected final @NotNull Vec3 origin;
@@ -36,7 +38,7 @@ public abstract class Hittable2D implements Hittable {
     }
 
     @Override
-    public @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range) {
+    public @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range, @Nullable RandomGenerator random) {
         var denominator = ray.direction().dot(normal);
         if (Math.abs(denominator) < 1e-8) return Optional.empty(); // parallel
 

src/main/java/eu/jonahbauer/raytracing/scene/hittable3d/Box.java

@@ -48,7 +48,7 @@ public final class Box implements Hittable, Target {
     }
 
     @Override
-    public @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range) {
+    public @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range, @Nullable RandomGenerator random) {
         // based on AABB#hit with additional detection of the side hit
         var origin = ray.origin();
         var direction = ray.direction();
@@ -103,13 +103,13 @@ public final class Box implements Hittable, Target {
             t = tmin;
             side = entry;
             frontFace = true;
-            material = materials[side.ordinal()];
+            material = materials[entry.ordinal()];
             normal = side.normal;
         } else if (range.surrounds(tmax) && materials[exit.ordinal()] != null) {
             t = tmax;
             side = exit;
             frontFace = false;
-            material = materials[side.ordinal()];
+            material = materials[exit.ordinal()];
             normal = side.normal.neg();
         } else {
             return Optional.empty();
@@ -130,7 +130,7 @@ public final class Box implements Hittable, Target {
     @Override
     public double getProbabilityDensity(@NotNull Vec3 origin, @NotNull Vec3 direction) {
         if (contains(origin)) return 1 / (4 * Math.PI);
-        if (hit(new Ray(origin, direction)).isEmpty()) return 0;
+        if (hit(new Ray(origin, direction), null).isEmpty()) return 0;
 
         var solidAngle = 0d;
         for (var s : Side.values()) {

src/main/java/eu/jonahbauer/raytracing/scene/hittable3d/ConstantMedium.java

@@ -10,15 +10,16 @@ import eu.jonahbauer.raytracing.scene.Hittable;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.Optional;
+import java.util.random.RandomGenerator;
 
 public record ConstantMedium(@NotNull Hittable boundary, double density, @NotNull IsotropicMaterial material) implements Hittable {
 
     @Override
-    public @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range) {
+    public @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range, @NotNull RandomGenerator random) {
-        var hit1 = boundary.hit(ray, Range.UNIVERSE);
+        var hit1 = boundary.hit(ray, Range.UNIVERSE, random);
         if (hit1.isEmpty()) return Optional.empty();
 
-        var hit2 = boundary.hit(ray, new Range(hit1.get().t() + 0.0001, Double.POSITIVE_INFINITY));
+        var hit2 = boundary.hit(ray, new Range(hit1.get().t() + 0.0001, Double.POSITIVE_INFINITY), random);
         if (hit2.isEmpty()) return Optional.empty();
 
         var tmin = Math.max(range.min(), hit1.get().t());
@@ -28,7 +29,7 @@ public record ConstantMedium(@NotNull Hittable boundary, double density, @NotNul
 
         var length = ray.direction().length();
         var distance = length * (tmax - tmin);
-        var hitDistance = - Math.log(Math.random()) / density;
+        var hitDistance = - Math.log(random.nextDouble()) / density;
         if (hitDistance > distance) return Optional.empty();
 
         var t = tmin + hitDistance / length;

src/main/java/eu/jonahbauer/raytracing/scene/hittable3d/Sphere.java

@@ -9,6 +9,7 @@ import eu.jonahbauer.raytracing.scene.HitResult;
 import eu.jonahbauer.raytracing.scene.Hittable;
 import eu.jonahbauer.raytracing.scene.Target;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.Objects;
 import java.util.Optional;
@@ -40,7 +41,7 @@ public final class Sphere implements Hittable, Target {
     }
 
     @Override
-    public @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range) {
+    public @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range, @Nullable RandomGenerator random) {
         var t = hit0(ray, range);
         if (Double.isNaN(t)) return Optional.empty();
 

src/main/java/eu/jonahbauer/raytracing/scene/transform/Transform.java

@@ -2,10 +2,8 @@ package eu.jonahbauer.raytracing.scene.transform;
 
 import eu.jonahbauer.raytracing.math.Range;
 import eu.jonahbauer.raytracing.math.Ray;
-import eu.jonahbauer.raytracing.math.Vec3;
 import eu.jonahbauer.raytracing.scene.HitResult;
 import eu.jonahbauer.raytracing.scene.Hittable;
-import eu.jonahbauer.raytracing.scene.Target;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.Objects;
@@ -24,7 +22,7 @@ public abstract class Transform implements Hittable {
     protected abstract @NotNull HitResult transform(@NotNull HitResult result);
 
     @Override
-    public final @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range) {
+    public final @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range, @NotNull RandomGenerator random) {
-        return object.hit(transform(ray), range).map(this::transform);
+        return object.hit(transform(ray), range, random).map(this::transform);
     }
 }

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

@@ -8,6 +8,7 @@ import org.jetbrains.annotations.Nullable;
 
 import java.util.Comparator;
 import java.util.List;
+import java.util.random.RandomGenerator;
 
 public final class HittableBinaryTree extends HittableCollection {
     private final @Nullable Hittable left;
@@ -46,17 +47,17 @@ public final class HittableBinaryTree extends HittableCollection {
     }
 
     @Override
-    public void hit(@NotNull Ray ray, @NotNull State state) {
+    public void hit(@NotNull Ray ray, @NotNull State state, @NotNull RandomGenerator random) {
         if (!bbox.hit(ray, state.getRange())) return;
         if (left instanceof HittableCollection coll) {
-            coll.hit(ray, state);
+            coll.hit(ray, state, random);
         } else if (left != null) {
-            hit(state, ray, left);
+            hit(state, ray, left, random);
         }
         if (right instanceof HittableCollection coll) {
-            coll.hit(ray, state);
+            coll.hit(ray, state, random);
         } else if (right != null) {
-            hit(state, ray, right);
+            hit(state, ray, right, random);
         }
     }
 

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

@@ -8,20 +8,21 @@ import org.jetbrains.annotations.NotNull;
 
 import java.util.Objects;
 import java.util.Optional;
+import java.util.random.RandomGenerator;
 
 public abstract class HittableCollection implements Hittable {
 
     @Override
-    public final @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range) {
+    public final @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range, @NotNull RandomGenerator random) {
         var state = new State(range);
-        hit(ray, state);
+        hit(ray, state, random);
         return state.getResult();
     }
 
-    public abstract void hit(@NotNull Ray ray, @NotNull State state);
+    public abstract void hit(@NotNull Ray ray, @NotNull State state, @NotNull RandomGenerator random);
 
-    protected static boolean hit(@NotNull State state, @NotNull Ray ray, @NotNull Hittable object) {
+    protected static boolean hit(@NotNull State state, @NotNull Ray ray, @NotNull Hittable object, @NotNull RandomGenerator random) {
-        var r = object.hit(ray, state.range);
+        var r = object.hit(ray, state.range, random);
         if (r.isPresent()) {
             if (state.range.surrounds(r.get().t())){
                 state.result = r.get();

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

@@ -7,6 +7,7 @@ import org.jetbrains.annotations.NotNull;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.random.RandomGenerator;
 
 public final class HittableList extends HittableCollection {
     private final @NotNull List<Hittable> objects;
@@ -22,8 +23,8 @@ public final class HittableList extends HittableCollection {
     }
 
     @Override
-    public void hit(@NotNull Ray ray, @NotNull State state) {
+    public void hit(@NotNull Ray ray, @NotNull State state, @NotNull RandomGenerator random) {
-        objects.forEach(object -> hit(state, ray, object));
+        objects.forEach(object -> hit(state, ray, object, random));
     }
 
     @Override