Alessio Quaglino
d070b1893e
For two colliding SDFs `A` and `B`, the function is `(A+B)+abs(max(A,B))`. This can also be written as `clearance + abs(intersection)`. This function has the following properties: - On the penetrating surface, it is equal to `A+B`, i.e. the clearance field which is the penetration depth. - The object boundary is a set of local minima in 3D space, since `abs(max(A, B))>0` away from the surface. - Along the penetrating surface, the maximum penetration is a local minimum of the clearance since this field is orthogonal to the midsurface field `A-B`, which acts as a support plane for the contact. [Level sets of the improved function for two colliding circles](https://www.wolframalpha.com/input?i=plot+sqrt%28x%5E2%2By%5E2%29-1+%2B+sqrt%28%28x-1%29%5E2%2B%28y-1%29%5E2%29-1+%2B+max%28max%28sqrt%28x%5E2%2By%5E2%29-1%2C+sqrt%28%28x-1%29%5E2%2B%28y-1%29%5E2%29-1%29%2C+0%29+-+min%28max%28sqrt%28x%5E2%2By%5E2%29-1%2C+sqrt%28%28x-1%29%5E2%2B%28y-1%29%5E2%29-1%29%2C+0%29+). PiperOrigin-RevId: 585106580 Change-Id: I5b18a1ef262ceb0a1ab8abcad8acfd6dc1992e2c
64 lines
2.1 KiB
C
64 lines
2.1 KiB
C
// Copyright 2021 DeepMind Technologies Limited
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef MUJOCO_SRC_ENGINE_ENGINE_COLLISION_SDF_H_
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#define MUJOCO_SRC_ENGINE_ENGINE_COLLISION_SDF_H_
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#include <mujoco/mjdata.h>
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#include <mujoco/mjexport.h>
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#include <mujoco/mjmodel.h>
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#include <mujoco/mjplugin.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef enum mjtSDFType_ { // signed distance function (SDF) type
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mjSDFTYPE_SINGLE = 0, // single SDF
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mjSDFTYPE_INTERSECTION, // max(A, B)
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mjSDFTYPE_MIDSURFACE, // A - B
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mjSDFTYPE_COLLISION, // A + B + abs(max(A, B))
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} mjtSDFType;
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struct mjSDF_ {
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const mjpPlugin** plugin;
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int* id;
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mjtSDFType type;
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mjtNum* relpos;
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mjtNum* relmat;
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mjtGeom* geomtype;
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};
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typedef struct mjSDF_ mjSDF;
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// signed distance function
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MJAPI mjtNum mjc_distance(const mjModel* m, const mjData* d, const mjSDF* s, const mjtNum x[3]);
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// gradient of sdf
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MJAPI void mjc_gradient(const mjModel* m, const mjData* d, const mjSDF* s, mjtNum gradient[3],
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const mjtNum x[3]);
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// collision between a height field and a signed distance field
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int mjc_HFieldSDF(const mjModel* m, const mjData* d, mjContact* con, int g1, int g2, mjtNum margin);
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// collision between a mesh and a signed distance field
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int mjc_MeshSDF(const mjModel* m, const mjData* d, mjContact* con, int g1, int g2, mjtNum margin);
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// collision between two signed distance fields
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int mjc_SDF(const mjModel* m, const mjData* d, mjContact* con, int g1, int g2, mjtNum margin);
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#ifdef __cplusplus
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}
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#endif
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#endif // MUJOCO_SRC_ENGINE_ENGINE_COLLISION_SDF_H_
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