Add membrane plugin (2D Flex elastic stiffness).

PiperOrigin-RevId: 574109411 Change-Id: I4a701d8189cecf540cd200bd30cb4582f3c7dd43
2023-10-17 04:54:37 -07:00
parent 110ade1435
commit d67b8c6251
13 changed files with 586 additions and 115 deletions
@@ -0,0 +1,67 @@
+// 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_MEMBRANE_H_
+#define MUJOCO_PLUGIN_ELASTICITY_MEMBRANE_H_
+
+#include <optional>
+#include <utility>
+#include <vector>
+
+#include <mujoco/mjdata.h>
+#include <mujoco/mjmodel.h>
+#include <mujoco/mjtnum.h>
+#include "elasticity.h"
+
+
+namespace mujoco::plugin::elasticity {
+
+class Membrane {
+ public:
+  // Returns a new Membrane instance or nullopt on failure.
+  static std::optional<Membrane> Create(const mjModel* m, mjData* d,
+                                     int instance);
+  Membrane(Membrane&&) = default;
+
+  Membrane& operator=(Membrane&& other) = default;
+
+  void Compute(const mjModel* m, mjData* d, int instance);
+
+  static void RegisterPlugin();
+
+  int f0;  // index of corresponding flex
+  int i0;  // index of first body
+  int nc;  // number of quads in the grid
+  int nv;  // number of vertices (bodies) in the Membrane
+  int nt;  // number of area elements (triangles)
+  int ne;  // number of edges in the Membrane
+
+  // connectivity info for mapping tetrahedra to edges and vertices
+  std::vector<Stencil2D> elements;          // triangles              (nt x 6)
+  std::vector<std::pair<int, int> > edges;  // edge to vertex map     (ne x 2)
+
+  // precomputed quantities
+  std::vector<mjtNum> metric;               // geom-induced metric     (nt x 9)
+
+  mjtNum thickness;
+
+ private:
+  Membrane(const mjModel* m, mjData* d, int instance, mjtNum nu, mjtNum E,
+           mjtNum thick, const std::vector<int>& simplex,
+           const std::vector<int>& edgeidx);
+};
+
+}  // namespace mujoco::plugin::elasticity
+
+#endif  // MUJOCO_PLUGIN_ELASTICITY_MEMBRANE_H_