Frustum cull fogs

Use CPU-side frustum culling to avoid drawing fogs when possible.

Also don't recalculate the near plane distance (for checking if fogs are
too close to the camera) every iteration when looping fogs.

Author: slipher

src/engine/renderer/tr_local.h

@@ -2823,7 +2823,7 @@ inline bool checkGLErrors()
 	void           R_LocalNormalToWorld( const vec3_t local, vec3_t world );
 	void           R_LocalPointToWorld( const vec3_t local, vec3_t world );
 
-	cullResult_t   R_CullBox( vec3_t worldBounds[ 2 ] );
+	cullResult_t   R_CullBox( const vec3_t worldBounds[ 2 ], int lastPlane = FRUSTUM_NEAR );
 	cullResult_t   R_CullLocalBox( vec3_t bounds[ 2 ] );
 	cullResult_t   R_CullLocalPointAndRadius( vec3_t origin, float radius );
 	cullResult_t   R_CullPointAndRadius( vec3_t origin, float radius );

src/engine/renderer/tr_main.cpp

@@ -341,7 +341,7 @@ R_CullBox
 Returns CULL_IN, CULL_CLIP, or CULL_OUT
 =================
 */
-cullResult_t R_CullBox( vec3_t worldBounds[ 2 ] )
+cullResult_t R_CullBox( const vec3_t worldBounds[ 2 ], int lastPlane )
 {
 	bool anyClip;
 	cplane_t *frust;
@@ -355,7 +355,7 @@ cullResult_t R_CullBox( vec3_t worldBounds[ 2 ] )
 	// check against frustum planes
 	anyClip = false;
 
-	for ( i = 0; i < FRUSTUM_PLANES; i++ )
+	for ( i = 0; i <= lastPlane; i++ )
 	{
 		frust = &tr.viewParms.frustum[ i ];
 
@@ -837,7 +837,7 @@ static void R_SetupFrustum()
 		MatrixAffineInverse(tr.viewParms.world.viewMatrix, invTransform);
 
 		//transform planes back to world space for culling
-		for (int i = 0; i <= FRUSTUM_NEAR; i++)
+		for (int i = 0; i < FRUSTUM_PLANES; i++)
 		{
 			plane_t plane;
 			VectorCopy(tr.viewParms.portalFrustum[i].normal, plane.normal);
@@ -881,13 +881,18 @@ static void R_SetupFrustum()
 			SetPlaneSignbits( &tr.viewParms.frustum[ i ] );
 		}
 
-		// Tr3B: set extra near plane which is required by the dynamic occlusion culling
 		tr.viewParms.frustum[ FRUSTUM_NEAR ].type = PLANE_NON_AXIAL;
 		VectorCopy( tr.viewParms.orientation.axis[ 0 ], tr.viewParms.frustum[ FRUSTUM_NEAR ].normal );
 
 		VectorMA( tr.viewParms.orientation.origin, r_znear->value, tr.viewParms.frustum[ FRUSTUM_NEAR ].normal, planeOrigin );
 		tr.viewParms.frustum[ FRUSTUM_NEAR ].dist = DotProduct( planeOrigin, tr.viewParms.frustum[ FRUSTUM_NEAR ].normal );
 		SetPlaneSignbits( &tr.viewParms.frustum[ FRUSTUM_NEAR ] );
+
+		tr.viewParms.frustum[ FRUSTUM_FAR ].type = PLANE_NON_AXIAL;
+		VectorCopy( tr.viewParms.orientation.axis[ 0 ], tr.viewParms.frustum[ FRUSTUM_FAR ].normal );
+		tr.viewParms.frustum[ FRUSTUM_FAR ].dist = tr.viewParms.zFar +
+			DotProduct( tr.viewParms.orientation.origin, tr.viewParms.frustum[ FRUSTUM_FAR ].normal );
+		SetPlaneSignbits( &tr.viewParms.frustum[ FRUSTUM_FAR ] );
 	}
 }
 

src/engine/renderer/tr_scene.cpp

@@ -229,13 +229,12 @@ static float NearPlaneCornerDist()
 // issue on the surface plane, since the GLSL calcs chop off overhang there. Note that
 // with original Q3 you are required to construct the fog so that it is impossible to pass
 // through non-surface planes at all.
-static bool R_InsideFog( int fognum )
+static bool R_InsideFog( int fognum, float tol )
 {
 	// TODO: with portals this should use the point at the view frustum near plane instead
 	const vec3_t &origin = tr.viewParms.orientation.origin;
 
 	const auto &bounds = tr.world->fogs[ fognum ].bounds;
-	float tol = NearPlaneCornerDist() + 0.1f;
 
 	for ( int i = 0; i < 3; i++ )
 	{
@@ -250,11 +249,18 @@ static bool R_InsideFog( int fognum )
 
 void R_AddFogBrushSurfaces()
 {
-	// TODO: incorporate them in the BSP?
+	float tol = NearPlaneCornerDist() + 0.1f;
+
 	for ( int i = 1; i < tr.world->numFogs; i++ )
 	{
 		const fog_t &fog = tr.world->fogs[ i ];
-		shader_t *shader = R_InsideFog( i )
+
+		if ( R_CullBox( fog.bounds, FRUSTUM_FAR ) == cullResult_t::CULL_OUT )
+		{
+			continue;
+		}
+
+		shader_t *shader = R_InsideFog( i, tol )
 			? fog.shader->fogInnerShader
 			: fog.shader->fogOuterShader;
 		R_AddDrawSurf( ( surfaceType_t *)&fog.surf, shader, -1 );