Fix branch wrapping #32

In this commit, the wrapping algorithm consider the position of neighbor's neighbor, so the cut normal of branch nodes would looks more natural. This commit also fix the radius calculation of the branch face.
Thanks @KeepFenDou for pointing out this issue.

CHANGELOGS.md

@@ -1,3 +1,12 @@
+Changes between 1.0.0-beta.16 and 1.0.0-beta.17:
+--------------------------------------------------
+- Remote IO Protocol
+- Uncombined Mode
+- User Defined Cut Face
+- Base Plane Constrain
+- Color Solubility
+- Crash Fix
+
 Changes between 1.0.0-beta.15 and 1.0.0-beta.16:
 --------------------------------------------------
 - Support onion skinning in pose editor  

CONTRIBUTORS

@@ -27,3 +27,4 @@ fornclake <https://www.reddit.com/user/fornclake>
 bvanevery <https://www.reddit.com/user/bvanevery>
 Toshio Araki <https://github.com/Toshiwoz>
 Evan Gruda <evangruda@ufl.edu>
+KeepFenDou <https://github.com/huxingyi/dust3d/issues/32>

thirdparty/nodemesh/nodemesh/builder.cpp

@@ -456,15 +456,23 @@ bool Builder::tryWrapMultipleBranchesForNode(size_t nodeIndex, std::vector<float
     std::vector<std::pair<std::vector<size_t>, QVector3D>> cutsForEdges;
     bool directSwallowed = false;
     for (size_t i = 0; i < node.edges.size(); ++i) {
-        const QVector3D &cutNormal = node.raysToNeibors[i];
+        QVector3D cutNormal = node.raysToNeibors[i];
         size_t edgeIndex = node.edges[i];
         size_t neighborIndex = m_edges[edgeIndex].neiborOf(nodeIndex);
         const auto &neighbor = m_nodes[neighborIndex];
+        if (neighbor.edges.size() == 2) {
+            size_t anotherEdgeIndex = neighbor.anotherEdge(edgeIndex);
+            size_t neighborsNeighborIndex = m_edges[anotherEdgeIndex].neiborOf(neighborIndex);
+            const auto &neighborsNeighbor = m_nodes[neighborsNeighborIndex];
+            cutNormal = ((cutNormal + (neighborsNeighbor.position - neighbor.position).normalized()) * 0.5).normalized();
+        }
         float distance = (neighbor.position - node.position).length();
         if (qFuzzyIsNull(distance))
             distance = 0.0001f;
-        float radiusFactor = 1.0 - (node.radius / distance);
+        float radiusRate = neighbor.radius / node.radius;
-        float radius = node.radius * radiusFactor + neighbor.radius * (1.0 - radiusFactor);
+        float tangentTriangleLongEdgeLength = distance + (radiusRate * distance / (1.0 - radiusRate));
+        float segmentLength = node.radius * (tangentTriangleLongEdgeLength - node.radius) / tangentTriangleLongEdgeLength;
+        float radius = segmentLength / std::sin(std::acos(node.radius / tangentTriangleLongEdgeLength));
         std::vector<QVector3D> cut;
         float offsetDistance = 0;
         offsetDistance = offsets[i] * (distance - node.radius - neighbor.radius);