From 21437090b80275f7967b7f5927ae0ead7f49d2e1 Mon Sep 17 00:00:00 2001
From: sfan5 <sfan5@live.de>
Date: Sat, 7 Dec 2024 12:59:40 +0100
Subject: [PATCH] Don't recalculate meshnode normals unnecessarily

---
 src/client/content_mapblock.cpp | 28 +++++++++++++++-------------
 src/client/mesh.cpp             |  4 ++--
 src/client/mesh.h               |  2 +-
 src/nodedef.cpp                 |  7 +++++--
 4 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/src/client/content_mapblock.cpp b/src/client/content_mapblock.cpp
index 2d294953a..25d303156 100644
--- a/src/client/content_mapblock.cpp
+++ b/src/client/content_mapblock.cpp
@@ -1644,7 +1644,6 @@ void MapblockMeshGenerator::drawMeshNode()
 {
 	u8 facedir = 0;
 	scene::IMesh* mesh;
-	bool private_mesh; // as a grab/drop pair is not thread-safe
 	int degrotate = 0;
 
 	if (cur_node.f->param_type_2 == CPT2_FACEDIR ||
@@ -1664,32 +1663,37 @@ void MapblockMeshGenerator::drawMeshNode()
 
 	if (cur_node.f->mesh_ptr) {
 		// clone and rotate mesh
-		private_mesh = true;
 		mesh = cloneMesh(cur_node.f->mesh_ptr);
+		bool modified = true;
 		if (facedir)
 			rotateMeshBy6dFacedir(mesh, facedir);
 		else if (degrotate)
 			rotateMeshXZby(mesh, 1.5f * degrotate);
-		recalculateBoundingBox(mesh);
-		meshmanip->recalculateNormals(mesh, true, false);
+		else
+			modified = false;
+		if (modified) {
+			recalculateBoundingBox(mesh);
+			// FIXME: we should rotate the normals too, instead of recalculating
+			meshmanip->recalculateNormals(mesh, true, false);
+		}
 	} else {
 		warningstream << "drawMeshNode(): missing mesh" << std::endl;
 		return;
 	}
 
-	int mesh_buffer_count = mesh->getMeshBufferCount();
-	for (int j = 0; j < mesh_buffer_count; j++) {
+	for (u32 j = 0; j < mesh->getMeshBufferCount(); j++) {
 		// Only up to 6 tiles are supported
-		const auto tile =  mesh->getTextureSlot(j);
+		const u32 tile = mesh->getTextureSlot(j);
 		useTile(MYMIN(tile, 5));
+
 		scene::IMeshBuffer *buf = mesh->getMeshBuffer(j);
 		video::S3DVertex *vertices = (video::S3DVertex *)buf->getVertices();
-		int vertex_count = buf->getVertexCount();
+		u32 vertex_count = buf->getVertexCount();
 
 		if (data->m_smooth_lighting) {
 			// Mesh is always private here. So the lighting is applied to each
 			// vertex right here.
-			for (int k = 0; k < vertex_count; k++) {
+			for (u32 k = 0; k < vertex_count; k++) {
 				video::S3DVertex &vertex = vertices[k];
 				vertex.Color = blendLightColor(vertex.Pos, vertex.Normal);
 				vertex.Pos += cur_node.origin;
@@ -1697,15 +1701,13 @@ void MapblockMeshGenerator::drawMeshNode()
 			collector->append(cur_node.tile, vertices, vertex_count,
 				buf->getIndices(), buf->getIndexCount());
 		} else {
-			// Don't modify the mesh, it may not be private here.
-			// Instead, let the collector process colors, etc.
+			// Let the collector process colors, etc.
 			collector->append(cur_node.tile, vertices, vertex_count,
 				buf->getIndices(), buf->getIndexCount(), cur_node.origin,
 				cur_node.color, cur_node.f->light_source);
 		}
 	}
-	if (private_mesh)
-		mesh->drop();
+	mesh->drop();
 }
 
 // also called when the drawtype is known but should have been pre-converted
diff --git a/src/client/mesh.cpp b/src/client/mesh.cpp
index 3f947ae50..012b9a45a 100644
--- a/src/client/mesh.cpp
+++ b/src/client/mesh.cpp
@@ -272,9 +272,9 @@ void rotateMeshYZby(scene::IMesh *mesh, f64 degrees)
 	rotateMesh<&v3f::Y, &v3f::Z>(mesh, degrees);
 }
 
-void rotateMeshBy6dFacedir(scene::IMesh *mesh, int facedir)
+void rotateMeshBy6dFacedir(scene::IMesh *mesh, u8 facedir)
 {
-	int axisdir = facedir >> 2;
+	u8 axisdir = facedir >> 2;
 	facedir &= 0x03;
 	switch (facedir) {
 		case 1: rotateMeshXZby(mesh, -90); break;
diff --git a/src/client/mesh.h b/src/client/mesh.h
index 5fd0ebb0e..3345e24f7 100644
--- a/src/client/mesh.h
+++ b/src/client/mesh.h
@@ -68,7 +68,7 @@ void setMeshColorByNormal(scene::IMesh *mesh, const v3f &normal,
 	Rotate the mesh by 6d facedir value.
 	Method only for meshnodes, not suitable for entities.
 */
-void rotateMeshBy6dFacedir(scene::IMesh *mesh, int facedir);
+void rotateMeshBy6dFacedir(scene::IMesh *mesh, u8 facedir);
 
 /*
 	Rotate the mesh around the axis and given angle in degrees.
diff --git a/src/nodedef.cpp b/src/nodedef.cpp
index 2301b179f..81348cf23 100644
--- a/src/nodedef.cpp
+++ b/src/nodedef.cpp
@@ -943,14 +943,17 @@ void ContentFeatures::updateTextures(ITextureSource *tsrc, IShaderSource *shdsrc
 		palette = tsrc->getPalette(palette_name);
 
 	if (drawtype == NDT_MESH && !mesh.empty()) {
-		// Meshnode drawtype
 		// Read the mesh and apply scale
 		mesh_ptr = client->getMesh(mesh);
 		if (mesh_ptr) {
 			v3f scale = v3f(BS) * visual_scale;
 			scaleMesh(mesh_ptr, scale);
 			recalculateBoundingBox(mesh_ptr);
-			meshmanip->recalculateNormals(mesh_ptr, true, false);
+			if (!checkMeshNormals(mesh_ptr)) {
+				infostream << "ContentFeatures: recalculating normals for mesh "
+					<< mesh << std::endl;
+				meshmanip->recalculateNormals(mesh_ptr, true, false);
+			}
 		}
 	}
 }