From 109612c7bc416d3ab45f30edbfc40a2ff7d090c4 Mon Sep 17 00:00:00 2001
From: netpro2k <netpro2k@gmail.com>
Date: Mon, 10 Jan 2022 19:41:31 -0800
Subject: [PATCH] Respect physicallyCorrectLights on lightmaps in
 MeshBasicMaterial

---
 src/renderers/shaders/ShaderLib/meshbasic.glsl.js | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/renderers/shaders/ShaderLib/meshbasic.glsl.js b/src/renderers/shaders/ShaderLib/meshbasic.glsl.js
index 3cd936dafe63b2..dd126b286d6a12 100644
--- a/src/renderers/shaders/ShaderLib/meshbasic.glsl.js
+++ b/src/renderers/shaders/ShaderLib/meshbasic.glsl.js
@@ -86,8 +86,17 @@ void main() {
 	// accumulation (baked indirect lighting only)
 	#ifdef USE_LIGHTMAP
 
-		vec4 lightMapTexel= texture2D( lightMap, vUv2 );
-		reflectedLight.indirectDiffuse += lightMapTexel.rgb * lightMapIntensity;
+		vec4 lightMapTexel = texture2D( lightMap, vUv2 );
+		vec3 lightMapIrradiance = lightMapTexel.rgb * lightMapIntensity;
+
+		// Lightmaps are the only source of "light" for basic materials, respect them being "phsyically correct"
+		#ifdef PHYSICALLY_CORRECT_LIGHTS
+
+			lightMapIrradiance *= RECIPROCAL_PI;
+
+		#endif
+
+		reflectedLight.indirectDiffuse += lightMapIrradiance;
 
 	#else