From 2039f496912216e36b69951f0c3980b21bf2fc59 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fernando=20Garc=C3=ADa=20Li=C3=B1=C3=A1n?=
 <fernandogarcialinan@gmail.com>
Date: Sun, 1 Aug 2021 08:34:49 +0200
Subject: [PATCH] Add missing call to glReadBuffer() when doing depth-only FBOs

---
 simgear/scene/viewer/CompositorPass.cxx | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/simgear/scene/viewer/CompositorPass.cxx b/simgear/scene/viewer/CompositorPass.cxx
index aca50056..0b047b61 100644
--- a/simgear/scene/viewer/CompositorPass.cxx
+++ b/simgear/scene/viewer/CompositorPass.cxx
@@ -395,8 +395,10 @@ PassBuilder::build(Compositor *compositor, const SGPropertyNode *root,
         // Explicitly let OpenGL know that there are no color buffers attached.
         // This is required on GL <4.2 contexts or the framebuffer will be
         // considered incomplete.
-        if (!color_buffer_present)
+        if (!color_buffer_present) {
             camera->setDrawBuffer(GL_NONE);
+            camera->setReadBuffer(GL_NONE);
+        }
     }
 
     return pass.release();