From b05f86296dd9efb766ef3f4d944433da268e6b04 Mon Sep 17 00:00:00 2001
From: Tyrann <tyrann@disenchant.net>
Date: Mon, 2 Oct 2006 20:14:01 +0930
Subject: [PATCH] [PATCH] qbsp: Avoid some unnecessary face splits

Save some memory in CSGFaces by not splitting faces outside the brush being
processed. Normally these faces will be split by the planes of the brush, even
if the brush doesn't intersect with it at all. This also saves some time in
MergeFaces, since we don't need to re-assemble these faces again.

Signed-off-by: Tyrann <tyrann@disenchant.net>
---
 qbsp/csg4.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/qbsp/csg4.c b/qbsp/csg4.c
index aff60d1a..caf33fa7 100644
--- a/qbsp/csg4.c
+++ b/qbsp/csg4.c
@@ -153,6 +153,53 @@ SplitFace(face_t *in, plane_t *split, face_t **front, face_t **back)
     FreeMem(in, FACE, 1);
 }
 
+/*
+=================
+CheckInside
+
+Quick test before running ClipInside; move any faces that are completely
+outside the brush to the outside list, without splitting them. This saves us
+time in mergefaces later on (and sometimes a lot of memory)
+=================
+*/
+static void
+CheckInside(brush_t *b)
+{
+    face_t *f, *bf, *next;
+    face_t *insidelist;
+    plane_t *plane, clip;
+    winding_t *w;
+
+    insidelist = NULL;
+    f = inside;
+    while (f) {
+	next = f->next;
+	plane = &pPlanes[f->planenum];
+	w = CopyWinding(&f->w);
+	for (bf = b->faces; bf; bf = bf->next) {
+	    clip = pPlanes[bf->planenum];
+	    if (!bf->planeside) {
+		VectorSubtract(vec3_origin, clip.normal, clip.normal);
+		clip.dist = -clip.dist;
+	    }
+	    w = ClipWinding(w, &clip, true);
+	    if (!w)
+		break;
+	}
+	if (!w) {
+	    /* The face is completely outside this brush */
+	    f->next = outside;
+	    outside = f;
+	} else {
+	    f->next = insidelist;
+	    insidelist = f;
+	    FreeMem(w, WINDING, 1);
+	}
+	f = next;
+    }
+    inside = insidelist;
+}
+
 /*
 =================
 ClipInside
@@ -385,6 +432,7 @@ CSGFaces(void)
 	    inside = outside;
 	    outside = NULL;
 
+	    CheckInside(b2);
 	    for (f = b2->faces; f; f = f->next)
 		ClipInside(f->planenum, f->planeside, overwrite);