play with camera settings and fix handedness of camera

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

@@ -3,6 +3,7 @@ package eu.jonahbauer.raytracing;
 import eu.jonahbauer.raytracing.material.DielectricMaterial;
 import eu.jonahbauer.raytracing.material.LambertianMaterial;
 import eu.jonahbauer.raytracing.material.MetallicMaterial;
+import eu.jonahbauer.raytracing.math.Vec3;
 import eu.jonahbauer.raytracing.render.Camera;
 import eu.jonahbauer.raytracing.render.Color;
 import eu.jonahbauer.raytracing.render.ImageFormat;
@@ -15,12 +16,17 @@ import java.nio.file.Path;
 public class Main {
     public static void main(String[] args) throws IOException {
         var scene = new Scene(
-                new Sphere(0, -100.5, 1, 100, new LambertianMaterial(new Color(0.8, 0.8, 0.0))),
-                new Sphere(0, 0, 1.2, 0.5, new LambertianMaterial(new Color(0.1, 0.2, 0.5))),
-                new Sphere(-1, 0, 1, 0.5, new DielectricMaterial(0.75)),
-                new Sphere(1, 0, 1, 0.5, new MetallicMaterial(new Color(0.8, 0.6, 0.2), 1.0))
+                new Sphere(0, -100.5, - 1, 100, new LambertianMaterial(new Color(0.8, 0.8, 0.0))),
+                new Sphere(0, 0, - 1.2, 0.5, new LambertianMaterial(new Color(0.1, 0.2, 0.5))),
+                new Sphere(-1, 0, - 1, 0.5, new DielectricMaterial(1.5)),
+                new Sphere(-1, 0, - 1, 0.4, new DielectricMaterial(1 / 1.5)),
+                new Sphere(1, 0, - 1, 0.5, new MetallicMaterial(new Color(0.8, 0.6, 0.2), 1.0))
+        );
+        var camera = new Camera(
+                800, 450,
+                16d / 9 * 2, 2d,
+                Vec3.ZERO.plus(Vec3.UNIT_Z).plus(Vec3.UNIT_Y).minus(Vec3.UNIT_X), new Vec3(0.25, -0.5, - 1)
         );
-        var camera = new Camera(512, 2, 16 / 9d);
 
         var image = camera.render(scene);
         ImageFormat.PNG.write(image, Path.of("scene-" + System.currentTimeMillis() + ".png"));

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

@@ -44,6 +44,12 @@ public record Vec3(double x, double y, double z) {
         return Optional.of(rOutPerp.plus(rOutParallel));
     }
 
+    public static @NotNull Vec3 rotate(@NotNull Vec3 vec, @NotNull Vec3 axis, double angle) {
+        Vec3 vxp = axis.cross(vec);
+        Vec3 vxvxp = axis.cross(vxp);
+        return vec.plus(vxp.times(Math.sin(angle))).plus(vxvxp.times(1 - Math.cos(angle)));
+    }
+
     public @NotNull Vec3 plus(@NotNull Vec3 b) {
         return new Vec3(this.x + b.x, this.y + b.y, this.z + b.z);
     }
@@ -60,6 +66,10 @@ public record Vec3(double x, double y, double z) {
         return new Vec3(this.x * b, this.y * b, this.z * b);
     }
 
+    public @NotNull Vec3 neg() {
+        return new Vec3(-x, -y, -z);
+    }
+
     public @NotNull Vec3 cross(@NotNull Vec3 b) {
         return new Vec3(
                 this.y() * b.z() - b.y() * this.z(),

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

@@ -49,7 +49,7 @@ public final class Camera {
      * @param viewportHeight the viewport height
      */
     public Camera(int width, int height, double viewportWidth, double viewportHeight) {
-        this(width, height, viewportWidth, viewportHeight, Vec3.ZERO, Vec3.UNIT_Z);
+        this(width, height, viewportWidth, viewportHeight, Vec3.ZERO, Vec3.UNIT_Z.neg());
     }
 
     public Camera(
@@ -73,11 +73,11 @@ public final class Camera {
         var d = direction.unit();
         var dXZ = direction.withY(0).unit();
 
-        var viewportU = new Vec3(dXZ.z(), 0, - dXZ.x()); // perpendicular to dXZ in xz-plane
+        var viewportU = new Vec3(- dXZ.z(), 0, dXZ.x()); // perpendicular to dXZ in xz-plane
         var viewportV = d.cross(viewportU); // perpendicular to viewportU and direction
 
         viewportU = viewportU.times(viewportWidth); // vector along the width of the viewport
-        viewportV = viewportV.times(- viewportHeight); // vector along the height of the viewport
+        viewportV = viewportV.times(viewportHeight); // vector along the height of the viewport
 
         this.pixelU = viewportU.div(width);
         this.pixelV = viewportV.div(height);