From 4941a86cbe9adeea4fde7a33f450403bc34283dc Mon Sep 17 00:00:00 2001
From: Eric Wasylishen <ewasylishen@gmail.com>
Date: Tue, 7 Jun 2022 19:49:39 -0600
Subject: [PATCH] qbsp: rest of fix for qbsp_q2_bmodel_collision, only needed
 on type-cleanup branch

---
 include/qbsp/brush.hh |  1 +
 qbsp/brush.cc         | 18 +++++++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/include/qbsp/brush.hh b/include/qbsp/brush.hh
index b0d675d3..63f0af07 100644
--- a/include/qbsp/brush.hh
+++ b/include/qbsp/brush.hh
@@ -53,3 +53,4 @@ void FreeBrushes(mapentity_t *ent);
 
 int FindPlane(const qplane3d &plane, int *side);
 int FindPositivePlane(int planenum);
+int FindPositivePlane(const qplane3d &plane, int *side);
diff --git a/qbsp/brush.cc b/qbsp/brush.cc
index a085484f..9b9d84b1 100644
--- a/qbsp/brush.cc
+++ b/qbsp/brush.cc
@@ -253,6 +253,22 @@ int FindPositivePlane(int planenum)
     return FindPlane(-plane, nullptr);
 }
 
+int FindPositivePlane(const qplane3d &plane, int *side)
+{
+    int planenum = FindPlane(plane, side);
+    int positive_plane = FindPositivePlane(planenum);
+
+    if (planenum == positive_plane) {
+        return planenum;
+    }
+
+    // planenum itself isn't positive, so flip the planeside and return the positive version
+    if (side) {
+        *side = !*side;
+    }
+    return positive_plane;
+}
+
 /*
 =============================================================================
 
@@ -394,7 +410,7 @@ static std::vector<face_t> CreateBrushFaces(const mapentity_t *src, hullbrush_t
         plane.dist = qv::dot(plane.normal, point);
 
         f.texinfo = hullnum > 0 ? 0 : mapface.texinfo;
-        f.planenum = FindPlane(plane, &f.planeside);
+        f.planenum = FindPositivePlane(plane, &f.planeside);
         f.src_entity = const_cast<mapentity_t *>(src); // FIXME: get rid of consts on src in the callers?
 
         CheckFace(&f, mapface);