add depth of field

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

@@ -28,6 +28,8 @@ public class Main {
                 .withPosition(new Vec3(-2, 2, 1))
                 .withTarget(new Vec3(0, 0, -1))
                 .withFieldOfView(Math.toRadians(20))
+                .withFocusDistance(3.4)
+                .withBlurAngle(Math.toRadians(10))
                 .build();
 
         var image = camera.render(scene);

src/main/java/eu/jonahbauer/raytracing/render/Camera.java

@@ -21,6 +21,7 @@ public final class Camera {
     private final int samplesPerPixel;
     private final int maxDepth;
     private final double gamma;
+    private final double blurRadius;
 
     // internal properties
     private final @NotNull Vec3 u;
@@ -42,7 +43,7 @@ public final class Camera {
         this.width = builder.imageWidth;
         this.height = builder.imageHeight;
 
-        var viewportHeight = 2 * Math.tan(0.5 * builder.fov);
+        var viewportHeight = 2 * Math.tan(0.5 * builder.fov) * builder.focusDistance;
         var viewportWidth = viewportHeight * ((double) width / height);
 
         this.origin = builder.position;
@@ -51,6 +52,7 @@ public final class Camera {
         this.samplesPerPixel = builder.samplePerPixel;
         this.maxDepth = builder.maxDepth;
         this.gamma = builder.gamma;
+        this.blurRadius = Math.tan(0.5 * builder.blurAngle) * builder.focusDistance;
 
         // project direction the horizontal plane
         var dXZ = direction.withY(0).unit();
@@ -63,7 +65,7 @@ public final class Camera {
         this.pixelU = u.times(viewportWidth / width);
         this.pixelV = v.times(viewportHeight / height);
 
-        this.pixel00 = origin.plus(direction)
+        this.pixel00 = origin.plus(direction.times(builder.focusDistance))
                 .minus(u.times(0.5 * viewportWidth)).minus(v.times(0.5 * viewportHeight))
                 .plus(pixelU.div(2)).plus(pixelV.div(2));
     }
@@ -97,6 +99,17 @@ public final class Camera {
     }
 
     private @NotNull Ray getRay(int x, int y) {
+        var origin = this.origin;
+        if (blurRadius > 0) {
+            double bu, bv;
+            do {
+                bu = 2 * Math.random() - 1;
+                bv = 2 * Math.random() - 1;
+            } while (bu * bu + bv * bv >= 1);
+
+            origin = origin.plus(u.times(blurRadius * bu)).plus(v.times(blurRadius * bv));
+        }
+
         return new Ray(origin, getPixel(x, y).minus(origin));
     }
 
@@ -147,6 +160,8 @@ public final class Camera {
         private double rotation = 0.0;
 
         private double fov = 0.5 * Math.PI;
+        private double focusDistance = 10;
+        private double blurAngle = 0.0;
 
         private int samplePerPixel = 100;
         private int maxDepth = 10;
@@ -190,6 +205,18 @@ public final class Camera {
             return this;
         }
 
+        public @NotNull Builder withFocusDistance(double focusDistance) {
+            if (focusDistance <= 0 || !Double.isFinite(focusDistance)) throw new IllegalArgumentException("focus distance must be positive");
+            this.focusDistance = focusDistance;
+            return this;
+        }
+
+        public @NotNull Builder withBlurAngle(double angle) {
+            if (angle < 0 || angle >= Math.PI || !Double.isFinite(angle)) throw new IllegalArgumentException("blur-angle must be in the range [0, π)");
+            this.blurAngle = angle;
+            return this;
+        }
+
         public @NotNull Builder withSamplesPerPixel(int samples) {
             if (samples <= 0) throw new IllegalArgumentException("samples must be positive");
             this.samplePerPixel = samples;