From 4175198d045674b6f5a62600a0e7d188403cebfa Mon Sep 17 00:00:00 2001
From: Filip Lundgren <45687559+ifiddynine@users.noreply.github.com>
Date: Sat, 26 Mar 2022 22:33:10 +0100
Subject: [PATCH] Detect Roughness factor exported by Blender

Matches the logic used by Blender's own FBX exporter / importer.
---
 code/AssetLib/FBX/FBXConverter.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/code/AssetLib/FBX/FBXConverter.cpp b/code/AssetLib/FBX/FBXConverter.cpp
index 32872108b..d446fd2e9 100644
--- a/code/AssetLib/FBX/FBXConverter.cpp
+++ b/code/AssetLib/FBX/FBXConverter.cpp
@@ -2161,6 +2161,9 @@ void FBXConverter::SetShadingPropertiesCommon(aiMaterial *out_mat, const Propert
     const float ShininessExponent = PropertyGet<float>(props, "ShininessExponent", ok);
     if (ok) {
         out_mat->AddProperty(&ShininessExponent, 1, AI_MATKEY_SHININESS);
+         // Match Blender behavior to extract roughness when only shininess is present
+        const float roughness = 1.0 - (sqrt(ShininessExponent) / 10.0);
+        out_mat->AddProperty(&roughness, 1, AI_MATKEY_ROUGHNESS_FACTOR);
     }
 
     // TransparentColor / TransparencyFactor... gee thanks FBX :rolleyes: