4 files changed, 47 insertions, 33 deletions

diff --git a/src/client/clientmap.cpp b/src/client/clientmap.cpp
index 46cb115aa..98e3f40d3 100644
--- a/src/client/clientmap.cpp
+++ b/src/client/clientmap.cpp
@@ -449,15 +449,7 @@ void ClientMap::renderMap(video::IVideoDriver* driver, s32 pass)
 	drawcall_count += draw_order.size();
 
 	for (auto &descriptor : draw_order) {
-		scene::IMeshBuffer *buf;
-		
-		if (descriptor.m_use_partial_buffer) {
-			descriptor.m_partial_buffer->beforeDraw();
-			buf = descriptor.m_partial_buffer->getBuffer();
-		}
-		else {
-			buf = descriptor.m_buffer;
-		}
+		scene::IMeshBuffer *buf = descriptor.getBuffer();
 
 		// Check and abort if the machine is swapping a lot
 		if (draw.getTimerTime() > 2000) {
@@ -501,7 +493,7 @@ void ClientMap::renderMap(video::IVideoDriver* driver, s32 pass)
 		m.setTranslation(block_wpos - offset);
 
 		driver->setTransform(video::ETS_WORLD, m);
-		driver->drawMeshBuffer(buf);
+		descriptor.draw(driver);
 		vertex_count += buf->getIndexCount();
 	}
 
@@ -812,15 +804,7 @@ void ClientMap::renderMapShadows(video::IVideoDriver *driver,
 	drawcall_count += draw_order.size();
 
 	for (auto &descriptor : draw_order) {
-		scene::IMeshBuffer *buf;
-		
-		if (descriptor.m_use_partial_buffer) {
-			descriptor.m_partial_buffer->beforeDraw();
-			buf = descriptor.m_partial_buffer->getBuffer();
-		}
-		else {
-			buf = descriptor.m_buffer;
-		}
+		scene::IMeshBuffer *buf = descriptor.getBuffer();
 
 		// Check and abort if the machine is swapping a lot
 		if (draw.getTimerTime() > 1000) {
@@ -845,7 +829,7 @@ void ClientMap::renderMapShadows(video::IVideoDriver *driver,
 		m.setTranslation(block_wpos - offset);
 
 		driver->setTransform(video::ETS_WORLD, m);
-		driver->drawMeshBuffer(buf);
+		descriptor.draw(driver);
 		vertex_count += buf->getIndexCount();
 	}
 
@@ -966,3 +950,18 @@ void ClientMap::updateTransparentMeshBuffers()
 	m_needs_update_transparent_meshes = false;
 }
 
+scene::IMeshBuffer* ClientMap::DrawDescriptor::getBuffer()
+{
+	return m_use_partial_buffer ? m_partial_buffer->getBuffer() : m_buffer;
+}
+
+void ClientMap::DrawDescriptor::draw(video::IVideoDriver* driver)
+{
+	if (m_use_partial_buffer) {
+		m_partial_buffer->beforeDraw();
+		driver->drawMeshBuffer(m_partial_buffer->getBuffer());
+		m_partial_buffer->afterDraw();
+	} else {
+		driver->drawMeshBuffer(m_buffer);
+	}
+}
diff --git a/src/client/clientmap.h b/src/client/clientmap.h
index 6d57f1911..823870c68 100644
--- a/src/client/clientmap.h
+++ b/src/client/clientmap.h
@@ -174,6 +174,9 @@ private:
 		DrawDescriptor(v3s16 pos, const PartialMeshBuffer *buffer) :
 			m_pos(pos), m_partial_buffer(buffer), m_reuse_material(false), m_use_partial_buffer(true)
 		{}
+
+		scene::IMeshBuffer* getBuffer();
+		void draw(video::IVideoDriver* driver);
 	};
 
 	Client *m_client;
diff --git a/src/client/mapblock_mesh.cpp b/src/client/mapblock_mesh.cpp
index 868573bf0..965dd5e29 100644
--- a/src/client/mapblock_mesh.cpp
+++ b/src/client/mapblock_mesh.cpp
@@ -1162,15 +1162,16 @@ void MapBlockBspTree::traverse(s32 node, v3f viewpoint, std::vector<s32> &output
 void PartialMeshBuffer::beforeDraw() const
 {
 	// Patch the indexes in the mesh buffer before draw
-
-	m_buffer->Indices.clear();
-	if (!m_vertex_indexes.empty()) {
-		for (auto index : m_vertex_indexes)
-			m_buffer->Indices.push_back(index);
-	}
+	m_buffer->Indices = std::move(m_vertex_indexes);
 	m_buffer->setDirty(scene::EBT_INDEX);
 }
 
+void PartialMeshBuffer::afterDraw() const
+{
+	// Take the data back
+	m_vertex_indexes = std::move(m_buffer->Indices.steal());
+}
+
 /*
 	MapBlockMesh
 */
@@ -1514,7 +1515,7 @@ void MapBlockMesh::updateTransparentBuffers(v3f camera_pos, v3s16 block_pos)
 		const auto &t = m_transparent_triangles[i];
 		if (current_buffer != t.buffer) {
 			if (current_buffer) {
-				m_transparent_buffers.emplace_back(current_buffer, current_strain);
+				m_transparent_buffers.emplace_back(current_buffer, std::move(current_strain));
 				current_strain.clear();
 			}
 			current_buffer = t.buffer;
@@ -1525,7 +1526,7 @@ void MapBlockMesh::updateTransparentBuffers(v3f camera_pos, v3s16 block_pos)
 	}
 
 	if (!current_strain.empty())
-		m_transparent_buffers.emplace_back(current_buffer, current_strain);
+		m_transparent_buffers.emplace_back(current_buffer, std::move(current_strain));
 }
 
 void MapBlockMesh::consolidateTransparentBuffers()
@@ -1539,7 +1540,7 @@ void MapBlockMesh::consolidateTransparentBuffers()
 	for (const auto &t : m_transparent_triangles) {
 		if (current_buffer != t.buffer) {
 			if (current_buffer != nullptr) {
-				this->m_transparent_buffers.emplace_back(current_buffer, current_strain);
+				this->m_transparent_buffers.emplace_back(current_buffer, std::move(current_strain));
 				current_strain.clear();
 			}
 			current_buffer = t.buffer;
@@ -1550,7 +1551,7 @@ void MapBlockMesh::consolidateTransparentBuffers()
 	}
 
 	if (!current_strain.empty()) {
-		this->m_transparent_buffers.emplace_back(current_buffer, current_strain);
+		this->m_transparent_buffers.emplace_back(current_buffer, std::move(current_strain));
 	}
 }
 
diff --git a/src/client/mapblock_mesh.h b/src/client/mapblock_mesh.h
index 72d128038..169b3a8c1 100644
--- a/src/client/mapblock_mesh.h
+++ b/src/client/mapblock_mesh.h
@@ -140,20 +140,31 @@ private:
 	s32 root = -1; // index of the root node
 };
 
+/*
+ * PartialMeshBuffer
+ *
+ * Attach alternate `Indices` to an existing mesh buffer, to make it possible to use different
+ * indices with the same vertex buffer.
+ *
+ * Irrlicht does not currently support this: `CMeshBuffer` ties together a single vertex buffer
+ * and a single index buffer. There's no way to share these between mesh buffers.
+ *
+ */
 class PartialMeshBuffer
 {
 public:
-	PartialMeshBuffer(scene::SMeshBuffer *buffer, const std::vector<u16> &vertex_indexes) :
-			m_buffer(buffer), m_vertex_indexes(vertex_indexes)
+	PartialMeshBuffer(scene::SMeshBuffer *buffer, std::vector<u16> &&vertex_indexes) :
+			m_buffer(buffer), m_vertex_indexes(std::move(vertex_indexes))
 	{}
 
 	scene::IMeshBuffer *getBuffer() const { return m_buffer; }
 	const std::vector<u16> &getVertexIndexes() const { return m_vertex_indexes; }
 
 	void beforeDraw() const;
+	void afterDraw() const;
 private:
 	scene::SMeshBuffer *m_buffer;
-	std::vector<u16> m_vertex_indexes;
+	mutable std::vector<u16> m_vertex_indexes;
 };
 
 /*