From 77c1a87e4ff5060b394e36d43b5df90e4db05b91 Mon Sep 17 00:00:00 2001
From: jbb01 <32650546+jbb01@users.noreply.github.com>
Date: Thu, 8 Aug 2024 19:31:57 +0200
Subject: [PATCH] fix a possible cause of NaNs

---
 .../raytracing/render/renderer/SimpleRenderer.java        | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/main/java/eu/jonahbauer/raytracing/render/renderer/SimpleRenderer.java b/src/main/java/eu/jonahbauer/raytracing/render/renderer/SimpleRenderer.java
index e3c6a1e..15a8ecc 100644
--- a/src/main/java/eu/jonahbauer/raytracing/render/renderer/SimpleRenderer.java
+++ b/src/main/java/eu/jonahbauer/raytracing/render/renderer/SimpleRenderer.java
@@ -180,7 +180,13 @@ public final class SimpleRenderer implements Renderer {
                     } else {
                         var mixed = new MixtureProbabilityDensityFunction(new TargetingProbabilityDensityFunction(hit.position(), scene.getLights()), pdf, 0.5);
                         var direction = mixed.generate(random);
-                        var factor = pdf.value(direction) / mixed.value(direction);
+
+                        var idealPdf = pdf.value(direction);
+                        var actualPdf = mixed.value(direction);
+                        if (actualPdf == 0) break; // when actualPdf is 0, the ray should have never been generated by mixed.generate
+
+                        var factor =  idealPdf / actualPdf;
+
                         attenuation = Color.multiply(attenuation, Color.multiply(a, factor));
                         ray = new Ray(hit.position(), direction);