Add shell plugin.

- Add bending passive force - Add two examples (plate and poncho) - Add stretching constraints for particles using tendons on mesh edges PiperOrigin-RevId: 566980584 Change-Id: Id0cd8e1084c05560f1008518a8afbd5311d563e2
2023-09-20 08:59:26 -07:00
parent c54aba15f9
commit dd5a7115cf
12 changed files with 2171 additions and 32 deletions
@@ -0,0 +1,79 @@
+// Copyright 2023 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef MUJOCO_PLUGIN_ELASTICITY_SHELL_H_
+#define MUJOCO_PLUGIN_ELASTICITY_SHELL_H_
+
+#include <optional>
+#include <vector>
+
+#include <mujoco/mjdata.h>
+#include <mujoco/mjmodel.h>
+#include <mujoco/mjtnum.h>
+
+
+namespace mujoco::plugin::elasticity {
+
+struct Stencil2D {
+  static constexpr int kNumEdges = 3;
+  static constexpr int kNumVerts = 3;
+  int vertices[kNumVerts];
+  int edges[kNumEdges];
+};
+
+struct StencilFlap {
+  static constexpr int kNumVerts = 4;
+  int vertices[kNumVerts];
+};
+
+class Shell {
+ public:
+  // Returns a new Shell instance or nullopt on failure.
+  static std::optional<Shell> Create(const mjModel* m, mjData* d,
+                                     int instance);
+  Shell(Shell&&) = default;
+
+  Shell& operator=(Shell&& other) = default;
+
+  void Compute(const mjModel* m, mjData* d, int instance);
+
+  static void RegisterPlugin();
+
+  int i0;  // index of first body
+  int nc;  // number of quads in the grid
+  int nv;  // number of vertices (bodies) in the Shell
+  int nt;  // number of area elements (triangles)
+  int ne;  // number of edges in the Shell
+
+  // connectivity info for mapping tetrahedra to edges and vertices
+  std::vector<Stencil2D> elements;          // triangles              (nt x 6)
+  std::vector<StencilFlap> flaps;           // adjacent triangles     (ne x 4)
+
+  // precomputed quantities
+  std::vector<mjtNum> position;             // previous-step positions (nv x 3)
+  std::vector<mjtNum> bending;              // bending Hessian         (ne x 16)
+
+  mjtNum damping;
+  mjtNum thickness;
+
+ private:
+  Shell(const mjModel* m, mjData* d, int instance, mjtNum nu, mjtNum E,
+        mjtNum damp, mjtNum thick, const std::vector<int>& face);
+
+  void CreateStencils(const std::vector<int>& face);
+};
+
+}  // namespace mujoco::plugin::elasticity
+
+#endif  // MUJOCO_PLUGIN_ELASTICITY_SHELL_H_