From a2a5b774aac766a87b2abba4d1d3f27d5b5809c0 Mon Sep 17 00:00:00 2001
From: Jeremy Hu <huxingyi@msn.com>
Date: Thu, 29 Nov 2018 11:55:55 +0930
Subject: [PATCH] Fix uvunwrap

The As-Rigid-As-Possible method of parametrization sometimes failed, so added Least-Squares-Conformal-Maps method as a fallback option.
---
 thirdparty/simpleuv/simpleuv/parametrize.cpp | 100 +++++++++++++------
 1 file changed, 71 insertions(+), 29 deletions(-)

diff --git a/thirdparty/simpleuv/simpleuv/parametrize.cpp b/thirdparty/simpleuv/simpleuv/parametrize.cpp
index 176f780c..2e01ac26 100644
--- a/thirdparty/simpleuv/simpleuv/parametrize.cpp
+++ b/thirdparty/simpleuv/simpleuv/parametrize.cpp
@@ -1,4 +1,5 @@
 #include <igl/arap.h>
+#include <igl/lscm.h>
 #include <igl/boundary_loop.h>
 #include <igl/harmonic.h>
 #include <igl/map_vertices_to_circle.h>
@@ -8,35 +9,9 @@
 namespace simpleuv
 {
 
-// Modified from the libigl example code
-// https://github.com/libigl/libigl/blob/master/tutorial/503_ARAPParam/main.cpp
-bool parametrize(const std::vector<Vertex> &verticies,
-        const std::vector<Face> &faces, 
-        std::vector<TextureCoord> &vertexUvs)
+void parametrizeUsingARAP(const Eigen::MatrixXd &V, const Eigen::MatrixXi &F, const Eigen::VectorXi &bnd, Eigen::MatrixXd &V_uv)
 {
-    if (verticies.empty() || faces.empty())
-        return false;
-    
-    //qDebug() << "parametrize vertices:" << verticies.size() << "faces:" << faces.size();
-
-    Eigen::MatrixXd V(verticies.size(), 3);
-    Eigen::MatrixXi F(faces.size(), 3);
-    Eigen::MatrixXd V_uv;
     Eigen::MatrixXd initial_guess;
-
-    for (decltype(verticies.size()) i = 0; i < verticies.size(); i++) {
-        const auto &vertex = verticies[i];
-        V.row(i) << vertex.xyz[0], vertex.xyz[1], vertex.xyz[2];
-    }
-
-    for (decltype(faces.size()) i = 0; i < faces.size(); i++) {
-        const auto &face = faces[i];
-        F.row(i) << face.indices[0], face.indices[1], face.indices[2];
-    }
-
-    // Compute the initial solution for ARAP (harmonic parametrization)
-    Eigen::VectorXi bnd;
-    igl::boundary_loop(F,bnd);
     Eigen::MatrixXd bnd_uv;
     igl::map_vertices_to_circle(V,bnd,bnd_uv);
 
@@ -58,15 +33,82 @@ bool parametrize(const std::vector<Vertex> &verticies,
     V_uv = initial_guess;
 
     arap_solve(bc,arap_data,V_uv);
+}
 
+void parametrizeUsingLSCM(const Eigen::MatrixXd &V, const Eigen::MatrixXi &F, const Eigen::VectorXi &bnd, Eigen::MatrixXd &V_uv)
+{
+    Eigen::VectorXi b(2,1);
+    b(0) = bnd(0);
+    b(1) = bnd(round(bnd.size()/2));
+    Eigen::MatrixXd bc(2,2);
+    bc<<0,0,1,0;
+
+    // LSCM parametrization
+    igl::lscm(V,F,b,bc,V_uv);
+}
+
+bool extractResult(const std::vector<Vertex> &verticies, const Eigen::MatrixXd &V_uv, std::vector<TextureCoord> &vertexUvs)
+{
+    vertexUvs.clear();
+    auto isCoordValid = [=](float coord) {
+        if (std::isnan(coord) || std::isinf(coord))
+            return false;
+        return true;
+    };
     for (decltype(verticies.size()) i = 0; i < verticies.size(); i++) {
         TextureCoord coord;
         coord.uv[0] = V_uv.row(i)[0];
         coord.uv[1] = V_uv.row(i)[1];
-        vertexUvs.push_back(coord);
+        if (isCoordValid(coord.uv[0]) && isCoordValid(coord.uv[1])) {
+            vertexUvs.push_back(coord);
+            continue;
+        }
+        vertexUvs.clear();
+        return false;
     }
-    
     return true;
 }
 
+// Modified from the libigl example code
+// https://github.com/libigl/libigl/blob/master/tutorial/503_ARAPParam/main.cpp
+bool parametrize(const std::vector<Vertex> &verticies,
+        const std::vector<Face> &faces, 
+        std::vector<TextureCoord> &vertexUvs)
+{
+    if (verticies.empty() || faces.empty())
+        return false;
+    
+    Eigen::MatrixXd V(verticies.size(), 3);
+    Eigen::MatrixXi F(faces.size(), 3);
+
+    for (decltype(verticies.size()) i = 0; i < verticies.size(); i++) {
+        const auto &vertex = verticies[i];
+        V.row(i) << vertex.xyz[0], vertex.xyz[1], vertex.xyz[2];
+    }
+
+    for (decltype(faces.size()) i = 0; i < faces.size(); i++) {
+        const auto &face = faces[i];
+        F.row(i) << face.indices[0], face.indices[1], face.indices[2];
+    }
+
+    Eigen::VectorXi bnd;
+    igl::boundary_loop(F,bnd);
+    
+    {
+        Eigen::MatrixXd V_uv;
+        parametrizeUsingARAP(V, F, bnd, V_uv);
+        if (extractResult(verticies, V_uv, vertexUvs))
+            return true;
+    }
+
+    {
+        Eigen::MatrixXd V_uv;
+        parametrizeUsingLSCM(V, F, bnd, V_uv);
+        if (extractResult(verticies, V_uv, vertexUvs))
+            return true;
+    }
+    
+    return false;
+}
+
 }