improve performance by precomputing parts of the AABB intersection algorithm

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

@@ -79,35 +79,39 @@ public record AABB(@NotNull Vec3 min, @NotNull Vec3 max) {
      * @return {@code true} iff the ray intersects this bounding box, {@code false} otherwise
      */
     public boolean hit(@NotNull Ray ray, @NotNull Range range) {
-        var origin = ray.origin();
-        var direction = ray.direction();
-        var invDirection = direction.inv();
-
-        // calculate t values for intersection points of ray with planes through min
-        var tmin = intersect(min(), origin, invDirection);
-        // calculate t values for intersection points of ray with planes through max
-        var tmax = intersect(max(), origin, invDirection);
-
-        // determine range of t for which the ray is inside this voxel
-        double tlmax = Double.NEGATIVE_INFINITY; // lower limit maximum
-        double tumin = Double.POSITIVE_INFINITY; // upper limit minimum
-
-        for (int i = 0; i < 3; i++) {
-            // classify t values as lower or upper limit based on ray direction
-            if (direction.get(i) >= 0) {
-                // min is lower limit and max is upper limit
-                if (tmin[i] > tlmax) tlmax = tmin[i];
-                if (tmax[i] < tumin) tumin = tmax[i];
-            } else {
-                // max is lower limit and min is upper limit
-                if (tmax[i] > tlmax) tlmax = tmax[i];
-                if (tmin[i] < tumin) tumin = tmin[i];
-            }
-        }
+        var invDirection = ray.getInvDirection();
+        var negInvOrigin = ray.getNegInvOrigin();
+
+        var tminX = Math.fma(min.x(), invDirection.x(), negInvOrigin.x());
+        var tminY = Math.fma(min.y(), invDirection.y(), negInvOrigin.y());
+        var tminZ = Math.fma(min.z(), invDirection.z(), negInvOrigin.z());
+
+        var tmaxX = Math.fma(max.x(), invDirection.x(), negInvOrigin.x());
+        var tmaxY = Math.fma(max.y(), invDirection.y(), negInvOrigin.y());
+        var tmaxZ = Math.fma(max.z(), invDirection.z(), negInvOrigin.z());
+
+        var tlmax = max(
+                Math.min(tminX, tmaxX),
+                Math.min(tminY, tmaxY),
+                Math.min(tminZ, tmaxZ)
+        );
+        var tumin = min(
+                Math.max(tminX, tmaxX),
+                Math.max(tminY, tmaxY),
+                Math.max(tminZ, tmaxZ)
+        );
 
         return tlmax < tumin && tumin >= range.min() && tlmax <= range.max();
     }
 
+    private static double max(double a, double b, double c) {
+        return Math.max(a, Math.max(b, c));
+    }
+
+    private static double min(double a, double b, double c) {
+        return Math.min(a, Math.min(b, c));
+    }
+
     /**
      * Computes the {@code t} values of the intersections of a ray with the axis-aligned planes through a point.
      * @param corner the point

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

@@ -6,17 +6,35 @@ import org.jetbrains.annotations.NotNull;
 
 import java.util.Objects;
 
-public record Ray(@NotNull Vec3 origin, @NotNull Vec3 direction, @NotNull SampledWavelengths lambda) {
-    public Ray {
-        Objects.requireNonNull(origin, "origin");
-        Objects.requireNonNull(direction, "direction");
-        Objects.requireNonNull(lambda, "lambda");
-    }
+public final class Ray {
+    private final @NotNull Vec3 origin;
+    private final @NotNull Vec3 direction;
+    private final @NotNull SampledWavelengths lambda;
+
+    private final @NotNull Vec3 inv;
+    private final @NotNull Vec3 negInvOrigin;
 
     public Ray(@NotNull Vec3 origin, @NotNull Vec3 direction) {
         this(origin, direction, SampledWavelengths.EMPTY);
     }
 
+    public Ray(@NotNull Vec3 origin, @NotNull Vec3 direction, @NotNull SampledWavelengths lambda) {
+        this.origin = Objects.requireNonNull(origin, "origin");
+        this.direction = Objects.requireNonNull(direction, "direction");
+        this.lambda = Objects.requireNonNull(lambda, "lambda");
+
+        this.inv = direction.inv();
+        this.negInvOrigin = inv.neg().times(origin);
+    }
+
+    private Ray(@NotNull Vec3 origin, @NotNull Vec3 direction, @NotNull SampledWavelengths lambda, @NotNull Vec3 inv, @NotNull Vec3 negInvOrigin) {
+        this.origin = origin;
+        this.direction = direction;
+        this.lambda = lambda;
+        this.inv = inv;
+        this.negInvOrigin = negInvOrigin;
+    }
+
     public @NotNull Vec3 at(double t) {
         return Vec3.fma(t, direction, origin);
     }
@@ -30,6 +48,50 @@ public record Ray(@NotNull Vec3 origin, @NotNull Vec3 direction, @NotNull Sample
     }
 
     public @NotNull Ray with(@NotNull SampledWavelengths lambda) {
-        return new Ray(origin, direction, lambda);
+        return new Ray(origin, direction, lambda, inv, negInvOrigin);
+    }
+
+    public @NotNull Vec3 origin() {
+        return origin;
     }
+
+    public @NotNull Vec3 direction() {
+        return direction;
+    }
+
+    public @NotNull SampledWavelengths lambda() {
+        return lambda;
+    }
+
+    public @NotNull Vec3 getInvDirection() {
+        return inv;
+    }
+
+    public @NotNull Vec3 getNegInvOrigin() {
+        return negInvOrigin;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == this) return true;
+        if (obj == null || obj.getClass() != this.getClass()) return false;
+        var that = (Ray) obj;
+        return Objects.equals(this.origin, that.origin) &&
+                Objects.equals(this.direction, that.direction) &&
+                Objects.equals(this.lambda, that.lambda);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(origin, direction, lambda);
+    }
+
+    @Override
+    public @NotNull String toString() {
+        return "Ray[" +
+                "origin=" + origin + ", " +
+                "direction=" + direction + ", " +
+                "lambda=" + lambda + ']';
+    }
+
 }

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

@@ -160,6 +160,14 @@ public record Vec3(double x, double y, double z) implements IVec3<Vec3> {
         );
     }
 
+    public static @NotNull Vec3 fma(@NotNull Vec3 a, @NotNull Vec3 b, @NotNull Vec3 c) {
+        return new Vec3(
+                Math.fma(a.x(), b.x(), c.x()),
+                Math.fma(a.y(), b.y(), c.y()),
+                Math.fma(a.z(), b.z(), c.z())
+        );
+    }
+
     public static double tripleProduct(@NotNull Vec3 a, @NotNull Vec3 b, @NotNull Vec3 c) {
         return a.x * b.y * c.z + a.y * b.z * c.x + a.z * b.x * c.y - c.x * b.y * a.z - c.y * b.z * a.x - c.z * b.x * a.y;
     }

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

@@ -7,10 +7,10 @@ import eu.jonahbauer.raytracing.render.material.Material;
 import eu.jonahbauer.raytracing.render.texture.Texture;
 import org.jetbrains.annotations.NotNull;
 
-import java.util.Objects;
+import java.util.random.RandomGenerator;
 
 /**
- * The result of a {@linkplain Hittable#hit(Ray, Range) hit}.
+ * The result of a {@linkplain Hittable#hit(Ray, Range, RandomGenerator) hit}.
  * @param t the {@code t} value at which the hit occurs
  * @param position the position of the hit
  * @param normal the surface normal at the hit position
@@ -24,10 +24,6 @@ public record HitResult(
         double t, @NotNull Vec3 position, @NotNull Vec3 normal, @NotNull Hittable target,
         @NotNull Material material, double u, double v, boolean isFrontFace
 ) implements Comparable<HitResult> {
-    public HitResult {
-        Objects.requireNonNull(position, "position");
-        normal = normal.unit();
-    }
 
     public @NotNull HitResult withPositionAndNormal(@NotNull Vec3 position, @NotNull Vec3 normal) {
         return new HitResult(t, position, normal, target, material, u, v, isFrontFace);