#5382: Expand welding capabilities. We treat a selection of exactly t…

…wo patches as special case where the selection order determines which patch's properties are preserved. When many things with at least two patches are selected, the algorithm will dive in an weld anything suitable (single pass), similar to what the CSG Merge algorithm is doing.

radiantcore/patch/algorithm/General.cpp

@@ -330,6 +330,52 @@ void weldPatches(const PatchNodePtr& patchNode1, const PatchNodePtr& patchNode2)
     scene::removeNodeFromParent(patchNode2);
 }
 
+void weldPatchPool()
+{
+    auto selectedPatches = selection::algorithm::getSelectedPatches();
+
+    // Sort these patches into buckets according to their parents
+    // This step may not be strictly necessary as weldPatches() checks the parents
+    // but we might save a bit of unnecessary comparison work
+    std::map<scene::INodePtr, std::vector<PatchNodePtr>> patchesByEntity;
+
+    for (const auto& patch : selectedPatches)
+    {
+        patchesByEntity[patch->getParent()].push_back(patch);
+    }
+
+    std::size_t numPatchesCreated = 0;
+
+    for (const auto& pair : patchesByEntity)
+    {
+        // Try to combine each patch of this list with the rest of them O(2n)
+        for (auto p1 = pair.second.begin(); p1 != pair.second.end(); ++p1)
+        {
+            if (!(*p1)->getParent()) continue; // patch has been merged already
+
+            for (auto p2 = p1 + 1; p2 != pair.second.end(); ++p2)
+            {
+                if (!(*p2)->getParent()) continue;// patch has been merged already
+
+                try
+                {
+                    weldPatches(*p1, *p2);
+                    ++numPatchesCreated;
+                }
+                catch (const cmd::ExecutionFailure&)
+                {
+                    continue; // failed to merge these two
+                }
+            }
+        }
+    }
+
+    if (numPatchesCreated == 0)
+    {
+        throw cmd::ExecutionFailure(_("Cannot weld, patches need have the same parent entity."));
+    }
+}
+
 void weldSelectedPatches(const cmd::ArgumentList& args)
 {
     if (args.size() > 0)
@@ -340,17 +386,26 @@ void weldSelectedPatches(const cmd::ArgumentList& args)
 
     auto& selectionInfo = GlobalSelectionSystem().getSelectionInfo();
 
-    // We need to have two patches selected
-    if (selectionInfo.totalCount != 2 || selectionInfo.patchCount != 2)
+    if (selectionInfo.totalCount == 2 || selectionInfo.patchCount == 2)
     {
-        throw cmd::ExecutionFailure(_("Cannot weld patches, select two patches to weld them."));
-    }
+        // Special handling for exactly two selected patches: the selection order is important
+        // Merge them and preserve the properties of the first selected patch
+        auto patch1 = std::dynamic_pointer_cast<PatchNode>(GlobalSelectionSystem().penultimateSelected());
+        auto patch2 = std::dynamic_pointer_cast<PatchNode>(GlobalSelectionSystem().ultimateSelected());
 
-    auto patch1 = std::dynamic_pointer_cast<PatchNode>(GlobalSelectionSystem().penultimateSelected());
-    auto patch2 = std::dynamic_pointer_cast<PatchNode>(GlobalSelectionSystem().ultimateSelected());
-
-    UndoableCommand cmd("WeldSelectedPatches");
-    weldPatches(patch1, patch2);
+        UndoableCommand cmd("WeldSelectedPatches");
+        weldPatches(patch1, patch2);
+    }
+    else if (selectionInfo.patchCount >= 2)
+    {
+        // We have many things with at least two patches selected, try to find a matching combo
+        UndoableCommand cmd("WeldSelectedPatches");
+        weldPatchPool();
+    }
+    else
+    {
+        throw cmd::ExecutionFailure(_("Cannot weld patches, select (at least) two patches with the same parent entity."));
+    }
 }
 
 } // namespace