From f7a695c212bea96887b32b859645f621fd8f1b48 Mon Sep 17 00:00:00 2001
From: sfence <sfence.software@gmail.com>
Date: Sat, 14 Dec 2024 17:01:06 +0100
Subject: [PATCH] Optimize raycast performance (#15233)

by skipping nodes not on the ray with selection boxes smaller than 1x1x1 early on
---
 doc/lua_api.md      |  2 ++
 src/environment.cpp |  6 ++++++
 src/nodedef.cpp     | 12 ++++++++++++
 src/nodedef.h       |  5 +++++
 4 files changed, 25 insertions(+)

diff --git a/doc/lua_api.md b/doc/lua_api.md
index 7fe464a30..d753b6b53 100644
--- a/doc/lua_api.md
+++ b/doc/lua_api.md
@@ -9948,6 +9948,8 @@ Used by `core.register_node`.
 
     selection_box = {
         -- see [Node boxes] for possibilities
+        -- Selection boxes that oversize node size can cause
+        -- significant performance drop of Raycasts.
     },
     -- Custom selection box definition. Multiple boxes can be defined.
     -- If "nodebox" drawtype is used and selection_box is nil, then node_box
diff --git a/src/environment.cpp b/src/environment.cpp
index fe582afd4..e66c7e2de 100644
--- a/src/environment.cpp
+++ b/src/environment.cpp
@@ -163,6 +163,8 @@ void Environment::continueRaycast(RaycastState *state, PointedThing *result_p)
 			break; // About to go out of bounds
 		}
 
+		const v3s16 pos_on_ray = state->m_iterator.m_current_node_pos;
+
 		// For each untested node
 		for (s16 z = new_nodes.MinEdge.Z; z <= new_nodes.MaxEdge.Z; z++)
 		for (s16 y = new_nodes.MinEdge.Y; y <= new_nodes.MaxEdge.Y; y++)
@@ -175,6 +177,10 @@ void Environment::continueRaycast(RaycastState *state, PointedThing *result_p)
 			if (!is_valid_position)
 				continue;
 
+			// Optimization: Skip non-oversized selection boxes for other positions.
+			if ((pos_on_ray != np) && !nodedef->get(n).has_big_selection_box)
+				continue;
+
 			PointabilityType pointable = isPointableNode(n, nodedef,
 					state->m_liquids_pointable,
 					state->m_pointabilities);
diff --git a/src/nodedef.cpp b/src/nodedef.cpp
index 81348cf23..0fde1b68e 100644
--- a/src/nodedef.cpp
+++ b/src/nodedef.cpp
@@ -1257,6 +1257,15 @@ inline void NodeDefManager::fixSelectionBoxIntUnion()
 		m_selection_box_union.MaxEdge.Z / BS - 0.5f);
 }
 
+inline void NodeDefManager::calcBigSelectionBox(content_t id, const ContentFeatures &def)
+{
+	aabb3f box_union;
+	getNodeBoxUnion(def.selection_box, def, &box_union);
+	m_content_features[id].has_big_selection_box =
+			(box_union.MinEdge.X < -BS/2) || (box_union.MaxEdge.X > BS/2) ||
+			(box_union.MinEdge.Y < -BS/2) || (box_union.MaxEdge.Y > BS/2) ||
+			(box_union.MinEdge.Z < -BS/2) || (box_union.MaxEdge.Z > BS/2);
+}
 
 void NodeDefManager::eraseIdFromGroups(content_t id)
 {
@@ -1312,6 +1321,7 @@ content_t NodeDefManager::set(const std::string &name, const ContentFeatures &de
 	getNodeBoxUnion(def.selection_box, def, &m_selection_box_union);
 	fixSelectionBoxIntUnion();
 
+	calcBigSelectionBox(id, def);
 	// Add this content to the list of all groups it belongs to
 	for (const auto &group : def.groups) {
 		const std::string &group_name = group.first;
@@ -1525,6 +1535,8 @@ void NodeDefManager::deSerialize(std::istream &is, u16 protocol_version)
 
 		getNodeBoxUnion(f.selection_box, f, &m_selection_box_union);
 		fixSelectionBoxIntUnion();
+
+		calcBigSelectionBox(i, f);
 	}
 
 	// Since liquid_alternative_flowing_id and liquid_alternative_source_id
diff --git a/src/nodedef.h b/src/nodedef.h
index c3f88ce83..e33f42699 100644
--- a/src/nodedef.h
+++ b/src/nodedef.h
@@ -425,6 +425,8 @@ struct ContentFeatures
 	NodeBox node_box;
 	NodeBox selection_box;
 	NodeBox collision_box;
+	//! Whether any selection box extent is > BS/2.
+	bool has_big_selection_box;
 
 	// --- SOUND PROPERTIES ---
 
@@ -774,6 +776,9 @@ private:
 	 */
 	void fixSelectionBoxIntUnion();
 
+	//! Calculates ContentFeatures::&has_big_selection_box
+	void calcBigSelectionBox(content_t id, const ContentFeatures &def);
+
 	//! Features indexed by ID.
 	std::vector<ContentFeatures> m_content_features;