From cfeb7766e7a1513492451f35dc65b86409655a7b Mon Sep 17 00:00:00 2001
From: Wenzel Jakob <wenzel.jakob@epfl.ch>
Date: Fri, 31 Jan 2020 12:12:09 +0100
Subject: [PATCH] fixed a serious issue in spectral interpolation (caught by
 @merlinND)

---
 src/libcore/spectrum.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libcore/spectrum.cpp b/src/libcore/spectrum.cpp
index 8f95a5cf..6e289161 100644
--- a/src/libcore/spectrum.cpp
+++ b/src/libcore/spectrum.cpp
@@ -703,7 +703,7 @@ Float InterpolatedSpectrum::eval(Float lambda) const {
               b  = m_wavelengths[idx1],
               fa = m_values[idx1-1],
               fb = m_values[idx1];
-        return math::lerp((lambda - a) / (b-a), fb, fa);
+        return math::lerp((lambda - a) / (b-a), fa, fb);
     } else if (idx2 == idx1+1) {
         /* Hit a value exactly */
         return m_values[idx1];