Ensure deterministic client occlusion culling and minor improvements

builtin/settingtypes.txt

@@ -2103,7 +2103,7 @@ server_side_occlusion_culling (Server-side occlusion culling) bool true
 #    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 20 2 2047
+block_cull_optimize_distance (Block cull optimize distance) int 25 2 2047
 
 [**Mapgen]
 

src/defaultsettings.cpp

@@ -397,7 +397,7 @@ 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", "20");
+	settings->setDefault("block_cull_optimize_distance", "25");
 	settings->setDefault("server_side_occlusion_culling", "true");
 	settings->setDefault("csm_restriction_flags", "62");
 	settings->setDefault("csm_restriction_noderange", "0");

src/map.cpp

@@ -1193,13 +1193,14 @@ bool Map::isBlockOccluded(v3s16 pos_relative, v3s16 cam_pos_nodes, bool simple_c
 	// 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 true;
+	// This should be only used in server occlusion cullung.
+	// The client recalculates the complete drawlist periodically,
+	// and random sampling could lead to visible flicker.
+	if (simple_check) {
+		v3s16 random_point(myrand_range(-bs2, bs2), myrand_range(-bs2, bs2), myrand_range(-bs2, bs2));
+		return isOccluded(cam_pos_nodes, pos_blockcenter + random_point, step, stepfac,
+					start_offset, end_offset, 1);
+	}
 
 	// Additional occlusion check, see comments in that function
 	v3s16 check;

src/map.h

@@ -305,9 +305,9 @@ class Map /*: public NodeContainer*/
 		}
 	}
 
-	bool isBlockOccluded(MapBlock *block, v3s16 cam_pos_nodes, bool simple_check = false)
+	bool isBlockOccluded(MapBlock *block, v3s16 cam_pos_nodes)
 	{
-		return isBlockOccluded(block->getPosRelative(), cam_pos_nodes, simple_check);
+		return isBlockOccluded(block->getPosRelative(), cam_pos_nodes, false);
 	}
 	bool isBlockOccluded(v3s16 pos_relative, v3s16 cam_pos_nodes, bool simple_check = false);