Pick a random ray, so that far missing block will eventually be shown

builtin/settingtypes.txt

@@ -2068,11 +2068,11 @@ block_send_optimize_distance (Block send optimize distance) int 4 2 32767
 server_side_occlusion_culling (Server-side occlusion culling) bool true
 
 #    At this distance the server will perform a simpler and cheaper occlusion check.
-#    Smaller values potentially improve performance, at the expense of visible
+#    Smaller values potentially improve performance, at the expense of temporarily visible
 #    rendering glitches (missing blocks).
 #    This is especially useful for very large viewing range (upwards of 500).
 #    Stated in mapblocks (16 nodes).
-block_cull_optimize_distance (Block cull optimize distance) int 25 2 32767
+block_cull_optimize_distance (Block cull optimize distance) int 20 2 32767
 
 [**Mapgen]
 

src/defaultsettings.cpp

@@ -392,7 +392,7 @@ void set_default_settings()
 	// This causes frametime jitter on client side, or does it?
 	settings->setDefault("max_block_send_distance", "12");
 	settings->setDefault("block_send_optimize_distance", "4");
-	settings->setDefault("block_cull_optimize_distance", "25");
+	settings->setDefault("block_cull_optimize_distance", "20");
 	settings->setDefault("server_side_occlusion_culling", "true");
 	settings->setDefault("csm_restriction_flags", "62");
 	settings->setDefault("csm_restriction_noderange", "0");

src/map.cpp

@@ -1180,9 +1180,13 @@ bool Map::isBlockOccluded(MapBlock *block, v3s16 cam_pos_nodes, bool simple_chec
 	// this is a HACK, we should think of a more precise algorithm
 	u32 needed_count = 2;
 
+	v3s16 random_point(myrand_range(-bs2, bs2), myrand_range(-bs2, bs2), myrand_range(-bs2, bs2));
+	if (!isOccluded(cam_pos_nodes, pos_blockcenter + random_point, step, stepfac,
+				start_offset, end_offset, needed_count))
+		return false;
+
 	if (simple_check)
-		return isOccluded(cam_pos_nodes, pos_blockcenter, step, stepfac,
-				start_offset, end_offset, needed_count);
+		return true;
 
 	// Additional occlusion check, see comments in that function
 	v3s16 check;