feat: Python 绑定 — pybind11 核心/曲线/网格模块

- 使用 pybind11 v2.11.1 (FetchContent) 构建 _vde 原生模块
- 模块化结构: bind_core.cpp / bind_curves.cpp / bind_mesh.cpp
- 暴露核心类型: Point2D, Point3D, Vector3D, AABB3D, Polygon2D
- 暴露曲线: BezierCurve, BSplineCurve, NurbsCurve
- 暴露网格: delaunay_2d/3d, DelaunayResult, HalfedgeMesh
- 变换函数: translate, rotate, scale 等
- Python 包 vde/ 含 __init__.py 及子模块封装
- setup.py 支持 pip install -e . 可编辑安装
- VDE_BUILD_PYTHON CMake 选项 (默认 OFF)，通过 -DVDE_BUILD_PYTHON=ON 启用

include/vde/sketch/constraint_solver.h

@@ -2,6 +2,7 @@
 #include "vde/core/point.h"
 #include <vector>
 #include <string>
+#include <unordered_map>
 
 namespace vde::sketch {
 using core::Point2D;
@@ -12,19 +13,33 @@ struct SketchLine { int id, p0, p1; };
 struct SketchCircle { int id, center; double radius; };
 
 enum class ConstraintType {
-    Horizontal, Vertical, Parallel, Perpendicular, Coincident,
-    EqualLength, Distance, Radius, Tangent, Concentric, FixedPoint
+    Horizontal,     // 水平线: y1 - y0 = 0
+    Vertical,       // 垂直线: x1 - x0 = 0
+    Parallel,       // 两线平行: cross(d0, d1) = 0
+    Perpendicular,  // 两线垂直: dot(d0, d1) = 0
+    Coincident,     // 两点重合: |p1-p0| = 0
+    EqualLength,    // 等长度: |d0| - |d1| = 0
+    Distance,       // 距离约束: |p1-p0| - d = 0
+    Radius,         // 半径约束
+    Tangent,        // 相切
+    Concentric,     // 同心
+    FixedPoint,     // 固定点（硬约束，排除变量）
+    Fixed,          // 固定点位置: x-x0=0, y-y0=0
+    Angle,          // 角度约束: atan2(cross(d0,d1), dot(d0,d1)) - θ = 0
 };
 
 struct Constraint {
     ConstraintType type;
-    std::vector<int> elements;
-    double value = 0.0;
+    std::vector<int> elements;  // 引用的元素索引
+    double value = 0.0;         // 距离/角度值
 };
 
 struct SolverResult {
-    bool converged = false; int iterations = 0; double residual = 0.0;
-    std::vector<Point2D> points; std::string message;
+    bool converged = false;
+    int iterations = 0;
+    double residual = 0.0;
+    std::vector<Point2D> points;
+    std::string message;
 };
 
 class ConstraintSolver {
@@ -33,18 +48,35 @@ public:
     int add_line(int p0, int p1);
     int add_circle(int center, double radius);
     void add_constraint(ConstraintType type, const std::vector<int>& elements, double val = 0.0);
-    void fix_point(int pid) { if(pid>=0&&pid<(int)points_.size()) points_[pid].fixed=true; }
+    void fix_point(int pid) {
+        if (pid >= 0 && pid < static_cast<int>(points_.size()))
+            points_[pid].fixed = true;
+    }
 
     [[nodiscard]] SolverResult solve(int max_iter = 100, double tol = 1e-8);
     [[nodiscard]] int degrees_of_freedom() const;
     [[nodiscard]] const std::vector<SketchPoint>& points() const { return points_; }
+    [[nodiscard]] Point2D get_point(int id) const;
 
 private:
     std::vector<SketchPoint> points_;
     std::vector<SketchLine> lines_;
     std::vector<SketchCircle> circles_;
     std::vector<Constraint> constraints_;
+
+    // 辅助：同步 vars → points_（用于 Jacobian 数值计算）
+    void sync_from_vars(const double* vars, int nv);
+
+    // 约束残差评估
     double eval_constraint(const Constraint& c) const;
+
+    // 约束方程数（Coincident/Fixed → 2，其他 → 1）
+    int count_equations(const Constraint& c) const;
+
+    // Jacobian 填充：将约束 ci 的 Jacobian 行写入矩阵 J
+    void fill_jacobian_rows(const Constraint& c, int ci,
+                            const std::vector<int>& row_map,
+                            double* J_data, int nv, int stride) const;
 };
 
 }  // namespace vde::sketch