Allow cheaper culling checks at a distance (#14073)

* Allow cheaper culling checks at a distance
* Pick a random ray, so that far missing block will eventually be shown

builtin/settingtypes.txt

@@ -2061,8 +2061,8 @@ liquid_update (Liquid update tick) float 1.0 0.001
 #    as well as sometimes on land).
 #    Setting this to a value greater than max_block_send_distance disables this
 #    optimization.
-#    Stated in mapblocks (16 nodes).
-block_send_optimize_distance (Block send optimize distance) int 4 2 32767
+#    Stated in MapBlocks (16 nodes).
+block_send_optimize_distance (Block send optimize distance) int 4 2 2047
 
 #    If enabled, the server will perform map block occlusion culling based on
 #    on the eye position of the player. This can reduce the number of blocks
@@ -2070,6 +2070,13 @@ block_send_optimize_distance (Block send optimize distance) int 4 2 32767
 #    invisible blocks, so that the utility of noclip mode is reduced.
 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 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 20 2 2047
+
 [**Mapgen]
 
 #    Size of mapchunks generated by mapgen, stated in mapblocks (16 nodes).

src/clientiface.cpp

@@ -59,6 +59,7 @@ RemoteClient::RemoteClient() :
 		g_settings->getFloat("full_block_send_enable_min_time_from_building")),
 	m_max_send_distance(g_settings->getS16("max_block_send_distance")),
 	m_block_optimize_distance(g_settings->getS16("block_send_optimize_distance")),
+	m_block_cull_optimize_distance(g_settings->getS16("block_cull_optimize_distance")),
 	m_max_gen_distance(g_settings->getS16("max_block_generate_distance")),
 	m_occ_cull(g_settings->getBool("server_side_occlusion_culling"))
 {
@@ -225,6 +226,8 @@ void RemoteClient::GetNextBlocks (
 		wanted_range);
 	const s16 d_opt = std::min(adjustDist(m_block_optimize_distance, prop_zoom_fov),
 		wanted_range);
+	const s16 d_cull_opt = std::min(adjustDist(m_block_cull_optimize_distance, prop_zoom_fov),
+		wanted_range);
 	const s16 d_blocks_in_sight = full_d_max * BS * MAP_BLOCKSIZE;
 
 	s16 d_max_gen = std::min(adjustDist(m_max_gen_distance, prop_zoom_fov),
@@ -355,7 +358,7 @@ void RemoteClient::GetNextBlocks (
 					continue;
 
 				if (m_occ_cull && !block_not_found &&
-						env->getMap().isBlockOccluded(block, cam_pos_nodes)) {
+						env->getMap().isBlockOccluded(block, cam_pos_nodes, d >= d_cull_opt)) {
 					m_blocks_occ.insert(p);
 					continue;
 				}

src/clientiface.h

@@ -397,6 +397,7 @@ private:
 	const float m_min_time_from_building;
 	const s16 m_max_send_distance;
 	const s16 m_block_optimize_distance;
+	const s16 m_block_cull_optimize_distance;
 	const s16 m_max_gen_distance;
 	const bool m_occ_cull;
 

src/defaultsettings.cpp

@@ -393,6 +393,7 @@ 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("server_side_occlusion_culling", "true");
 	settings->setDefault("csm_restriction_flags", "62");
 	settings->setDefault("csm_restriction_noderange", "0");

src/map.cpp

@@ -1155,7 +1155,7 @@ bool Map::isOccluded(const v3s16 &pos_camera, const v3s16 &pos_target,
 	return false;
 }
 
-bool Map::isBlockOccluded(MapBlock *block, v3s16 cam_pos_nodes)
+bool Map::isBlockOccluded(MapBlock *block, v3s16 cam_pos_nodes, bool simple_check)
 {
 	// Check occlusion for center and all 8 corners of the mapblock
 	// Overshoot a little for less flickering
@@ -1193,6 +1193,14 @@ bool Map::isBlockOccluded(MapBlock *block, v3s16 cam_pos_nodes)
 	// 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;
+
 	// Additional occlusion check, see comments in that function
 	v3s16 check;
 	if (determineAdditionalOcclusionCheck(cam_pos_nodes, block->getBox(), check)) {

src/map.h

@@ -305,7 +305,7 @@ public:
 		}
 	}
 
-	bool isBlockOccluded(MapBlock *block, v3s16 cam_pos_nodes);
+	bool isBlockOccluded(MapBlock *block, v3s16 cam_pos_nodes, bool simple_check = false);
 protected:
 	IGameDef *m_gamedef;