From cbbae0c9bfcf968d62d7c5854e8f30ea757a308e Mon Sep 17 00:00:00 2001
From: Alibek Omarov <a1ba.omarov@gmail.com>
Date: Mon, 6 Apr 2026 08:25:41 +0500
Subject: [PATCH] ref: gl: simplify backface culling checks in frustum class

---
 ref/gl/gl_cull.c    | 40 ++++++++++++++--------------------------
 ref/gl/gl_frustum.c | 17 ++++++-----------
 2 files changed, 20 insertions(+), 37 deletions(-)

diff --git a/ref/gl/gl_cull.c b/ref/gl/gl_cull.c
index 27f394a4..a897db8a 100644
--- a/ref/gl/gl_cull.c
+++ b/ref/gl/gl_cull.c
@@ -67,10 +67,10 @@ int R_CullSurface( const msurface_t *surf, const gl_frustum_t *frustum, uint cli
 {
 	cl_entity_t	*e = RI.currententity;
 
-	if( !e || !surf || !surf->texinfo || !surf->texinfo->texture )
+	if( unlikely( !e || !surf || !surf->texinfo || !surf->texinfo->texture ))
 		return CULL_OTHER;
 
-	if( r_nocull.value )
+	if( unlikely( r_nocull.value ))
 		return CULL_VISIBLE;
 
 	// world surfaces can be culled by vis frame too
@@ -78,9 +78,10 @@ int R_CullSurface( const msurface_t *surf, const gl_frustum_t *frustum, uint cli
 		return CULL_VISFRAME;
 
 	// only static ents can be culled by frustum
-	if( !R_StaticEntity( e )) frustum = NULL;
+	if( !R_StaticEntity( e ))
+		frustum = NULL;
 
-	if( !VectorIsNull( surf->plane->normal ))
+	if( glState.faceCull != GL_NONE && !VectorIsNull( surf->plane->normal ))
 	{
 		float	dist;
 
@@ -95,35 +96,22 @@ int R_CullSurface( const msurface_t *surf, const gl_frustum_t *frustum, uint cli
 		}
 		else dist = PlaneDiff( tr.modelorg, surf->plane );
 
+		if( FBitSet( surf->flags, SURF_PLANEBACK ))
+			dist = -dist;
+
 		if( glState.faceCull == GL_FRONT )
 		{
-			if( FBitSet( surf->flags, SURF_PLANEBACK ))
-			{
-				if( dist >= -BACKFACE_EPSILON )
-					return CULL_BACKSIDE; // wrong side
-			}
-			else
-			{
-				if( dist <= BACKFACE_EPSILON )
-					return CULL_BACKSIDE; // wrong side
-			}
+			if( dist <= BACKFACE_EPSILON )
+				return CULL_BACKSIDE;
 		}
-		else if( glState.faceCull == GL_BACK )
+		else // if( glState.faceCull == GL_BACK )
 		{
-			if( FBitSet( surf->flags, SURF_PLANEBACK ))
-			{
-				if( dist <= BACKFACE_EPSILON )
-					return CULL_BACKSIDE; // wrong side
-			}
-			else
-			{
-				if( dist >= -BACKFACE_EPSILON )
-					return CULL_BACKSIDE; // wrong side
-			}
+			if( dist >= -BACKFACE_EPSILON )
+				return CULL_BACKSIDE;
 		}
 	}
 
-	if( frustum && GL_FrustumCullBox( frustum, surf->info->mins, surf->info->maxs, clipflags ))
+	if( frustum && clipflags && GL_FrustumCullBox( frustum, surf->info->mins, surf->info->maxs, clipflags ))
 		return CULL_FRUSTUM;
 
 	return CULL_VISIBLE;
diff --git a/ref/gl/gl_frustum.c b/ref/gl/gl_frustum.c
index 0e4b2103..06e54af6 100644
--- a/ref/gl/gl_frustum.c
+++ b/ref/gl/gl_frustum.c
@@ -99,15 +99,14 @@ void GL_FrustumInitOrtho( gl_frustum_t *out, float xLeft, float xRight, float yT
 // cull methods
 qboolean GL_FrustumCullBox( const gl_frustum_t *out, const vec3_t mins, const vec3_t maxs, int userClipFlags )
 {
-	int	iClipFlags;
+	int iClipFlags = userClipFlags != 0 ? userClipFlags : out->clipFlags;
 	int	i, bit;
 
-	if( r_nocull.value )
+	if( unlikely( r_nocull.value ))
 		return false;
 
-	if( userClipFlags != 0 )
-		iClipFlags = userClipFlags;
-	else iClipFlags = out->clipFlags;
+	if( !iClipFlags )
+		return false;
 
 	for( i = FRUSTUM_PLANES, bit = 1; i > 0; i--, bit <<= 1 )
 	{
@@ -160,16 +159,12 @@ qboolean GL_FrustumCullBox( const gl_frustum_t *out, const vec3_t mins, const ve
 
 qboolean GL_FrustumCullSphere( const gl_frustum_t *out, const vec3_t center, float radius, int userClipFlags )
 {
-	int	iClipFlags;
+	int iClipFlags = userClipFlags != 0 ? userClipFlags : out->clipFlags;
 	int	i, bit;
 
-	if( r_nocull.value )
+	if( unlikely( r_nocull.value ))
 		return false;
 
-	if( userClipFlags != 0 )
-		iClipFlags = userClipFlags;
-	else iClipFlags = out->clipFlags;
-
 	for( i = FRUSTUM_PLANES, bit = 1; i > 0; i--, bit <<= 1 )
 	{
 		const mplane_t *p = &out->planes[FRUSTUM_PLANES - i];