skip unnecessary UV calculations

src/main/java/eu/jonahbauer/raytracing/render/material/IsotropicMaterial.java

@@ -3,6 +3,7 @@ package eu.jonahbauer.raytracing.render.material;
 import eu.jonahbauer.raytracing.math.Ray;
 import eu.jonahbauer.raytracing.math.Vec3;
 import eu.jonahbauer.raytracing.render.texture.Color;
+import eu.jonahbauer.raytracing.render.texture.Texture;
 import eu.jonahbauer.raytracing.scene.HitResult;
 import org.jetbrains.annotations.NotNull;
 
@@ -14,4 +15,9 @@ public record IsotropicMaterial(@NotNull Color albedo) implements Material {
     public @NotNull Optional<ScatterResult> scatter(@NotNull Ray ray, @NotNull HitResult hit, @NotNull RandomGenerator random) {
         return Optional.of(new ScatterResult(new Ray(hit.position(), Vec3.random(random, true)), albedo()));
     }
+
+    @Override
+    public @NotNull Texture texture() {
+        return albedo();
+    }
 }

src/main/java/eu/jonahbauer/raytracing/render/material/Material.java

@@ -2,6 +2,7 @@ package eu.jonahbauer.raytracing.render.material;
 
 import eu.jonahbauer.raytracing.math.Ray;
 import eu.jonahbauer.raytracing.render.texture.Color;
+import eu.jonahbauer.raytracing.render.texture.Texture;
 import eu.jonahbauer.raytracing.scene.HitResult;
 import org.jetbrains.annotations.NotNull;
 
@@ -11,6 +12,8 @@ import java.util.random.RandomGenerator;
 
 public interface Material {
 
+    @NotNull Texture texture();
+
     @NotNull Optional<ScatterResult> scatter(@NotNull Ray ray, @NotNull HitResult hit, @NotNull RandomGenerator random);
 
     default @NotNull Color emitted(@NotNull HitResult hit) {

src/main/java/eu/jonahbauer/raytracing/render/texture/CheckerTexture.java

@@ -14,4 +14,9 @@ public record CheckerTexture(double scale, @NotNull Texture even, @NotNull Textu
         var even = (x + y + z) % 2 == 0;
         return even ? even().get(u, v, p) : odd().get(u, v, p);
     }
+
+    @Override
+    public boolean isUVRequired() {
+        return even.isUVRequired() || odd.isUVRequired();
+    }
 }

src/main/java/eu/jonahbauer/raytracing/render/texture/Color.java

@@ -94,6 +94,11 @@ public record Color(double r, double g, double b) implements Texture {
         return this;
     }
 
+    @Override
+    public boolean isUVRequired() {
+        return false;
+    }
+
     private static int toInt(double value) {
         return Math.clamp((int) (255.99 * value), 0, 255);
     }

src/main/java/eu/jonahbauer/raytracing/render/texture/PerlinTexture.java

@@ -144,4 +144,9 @@ public final class PerlinTexture implements Texture {
         }
         return accum;
     }
+
+    @Override
+    public boolean isUVRequired() {
+        return false;
+    }
 }

src/main/java/eu/jonahbauer/raytracing/render/texture/Texture.java

@@ -10,4 +10,8 @@ public interface Texture {
     }
 
     @NotNull Color get(double u, double v, @NotNull Vec3 p);
+
+    default boolean isUVRequired() {
+        return true;
+    }
 }

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

@@ -82,8 +82,9 @@ public record Box(@NotNull AABB box, @NotNull Material material) implements Hitt
         var side = frontFace ? entry : exit;
         var normal = frontFace ? side.normal : side.normal.neg();
         var position = ray.at(t);
-        var u = side.getTextureU(box, position);
-        var v = side.getTextureV(box, position);
+        var uv = material().texture().isUVRequired();
+        var u = uv ? side.getTextureU(box, position) : Double.NaN;
+        var v = uv ? side.getTextureV(box, position) : Double.NaN;
         return Optional.of(new HitResult(t, position, normal, material, u, v, frontFace));
     }
 

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

@@ -52,11 +52,17 @@ public final class Sphere implements Hittable {
         var normal = position.minus(center).div(radius);
         var frontFace = normal.times(ray.direction()) < 0;
 
-        var theta = Math.acos(- normal.y());
-        var phi = Math.atan2(- normal.z(), normal.x()) + Math.PI;
-
-        var u = phi / (2 * Math.PI);
-        var v = theta / Math.PI;
+        double u;
+        double v;
+        if (material.texture().isUVRequired()) {
+            var theta = Math.acos(-normal.y());
+            var phi = Math.atan2(-normal.z(), normal.x()) + Math.PI;
+            u = phi / (2 * Math.PI);
+            v = theta / Math.PI;
+        } else {
+            u = Double.NaN;
+            v = Double.NaN;
+        }
 
         return Optional.of(new HitResult(
                 t, position, frontFace ? normal : normal.neg(),