Add Signed Distance Field to collision geometries.

PiperOrigin-RevId: 557507088
Change-Id: I358a642407aee1ba8dfc9d405eb9a4f609435fe9

include/mujoco/mjplugin.h

@@ -56,6 +56,7 @@ typedef enum mjtPluginCapabilityBit_ {
   mjPLUGIN_ACTUATOR = 1<<0,       // actuator forces
   mjPLUGIN_SENSOR   = 1<<1,       // sensor measurements
   mjPLUGIN_PASSIVE  = 1<<2,       // passive forces
+  mjPLUGIN_SDF      = 1<<3,       // signed distance fields
 } mjtPluginCapabilityBit;
 
 struct mjpPlugin_ {
@@ -93,6 +94,20 @@ struct mjpPlugin_ {
 
   // called by mjv_updateScene (optional)
   void (*visualize)(const mjModel*m, mjData* d, const mjvOption* opt, mjvScene* scn, int instance);
+
+  // methods specific to signed distance fields (optional)
+
+  // signed distance from the surface
+  mjtNum (*sdf_distance)(const mjtNum point[3], const mjData* d, int instance);
+
+  // gradient of distance with respect to local coordinates
+  void (*sdf_gradient)(mjtNum gradient[3], const mjtNum point[3], const mjData* d, int instance);
+
+  // called during compilation for marching cubes
+  mjtNum (*sdf_staticdistance)(const mjtNum point[3], const mjtNum* attributes);
+
+  // bounding box of implicit surface
+  void (*sdf_aabb)(mjtNum aabb[6], const mjtNum* attributes);
 };
 typedef struct mjpPlugin_ mjpPlugin;