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add total internal reflection

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jbb01 2024-08-03 22:16:53 +02:00
parent 088263b344
commit 82b38d4501
3 changed files with 25 additions and 6 deletions
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2
src/main/java/eu/jonahbauer/raytracing/Main.java
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@ -17,7 +17,7 @@ public class Main {
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(1.5)),
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))
);
var camera = new Camera(512, 2, 16 / 9d);

18
src/main/java/eu/jonahbauer/raytracing/material/DielectricMaterial.java
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@ -12,7 +12,21 @@ public record DielectricMaterial(double refractionIndex) implements Material {
@Override
public @NotNull Optional<ScatterResult> scatter(@NotNull Ray ray, @NotNull HitResult hit) {
var ri = hit.frontFace() ? (1 / refractionIndex) : refractionIndex;
var refracted = Vec3.refract(ray.direction(), hit.normal(), ri);
return Optional.of(new ScatterResult(new Ray(hit.position(), refracted), Color.WHITE));
var cosTheta = Math.min(- ray.direction().unit().times(hit.normal()), 1.0);
var reflectance = reflectance(cosTheta);
var reflect = reflectance > Math.random();
var newDirection = (reflect ? Optional.<Vec3>empty() : Vec3.refract(ray.direction(), hit.normal(), ri))
.orElseGet(() -> Vec3.reflect(ray.direction(), hit.normal()));
return Optional.of(new ScatterResult(new Ray(hit.position(), newDirection), Color.WHITE));
}
private double reflectance(double cos) {
// use schlick's approximation for reflectance
var r0 = (1 - refractionIndex) / (1 + refractionIndex);
r0 = r0 * r0;
return r0 + (1 - r0) * (1 - cos) * (1 - cos) * (1 - cos) * (1 - cos) * (1 - cos);
}
}

11
src/main/java/eu/jonahbauer/raytracing/math/Vec3.java
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@ -2,6 +2,8 @@ package eu.jonahbauer.raytracing.math;
import org.jetbrains.annotations.NotNull;
import java.util.Optional;
public record Vec3(double x, double y, double z) {
public static final Vec3 ZERO = new Vec3(0, 0, 0);
public static final Vec3 UNIT_X = new Vec3(1, 0, 0);
@ -31,12 +33,15 @@ public record Vec3(double x, double y, double z) {
return vec.minus(normal.times(2 * normal.times(vec)));
}
public static @NotNull Vec3 refract(@NotNull Vec3 vec, @NotNull Vec3 normal, double index) {
public static @NotNull Optional<Vec3> refract(@NotNull Vec3 vec, @NotNull Vec3 normal, double ri) {
vec = vec.unit();
var cosTheta = Math.min(- vec.times(normal), 1.0);
var rOutPerp = vec.plus(normal.times(cosTheta)).times(index);
var sinTheta = Math.sqrt(1 - cosTheta * cosTheta);
if (ri * sinTheta > 1) return Optional.empty();
var rOutPerp = vec.plus(normal.times(cosTheta)).times(ri);
var rOutParallel = normal.times(- Math.sqrt(Math.abs(1 - rOutPerp.squared())));
return rOutPerp.plus(rOutParallel);
return Optional.of(rOutPerp.plus(rOutParallel));
}
public @NotNull Vec3 plus(@NotNull Vec3 b) {