Move tactile sensor to the engine.

PiperOrigin-RevId: 788863133
Change-Id: I3172ebb7641fa8146469da25cba7db794760e7b1

src/xml/xml_native_reader.cc

@@ -492,6 +492,7 @@ const char* MJCF[nMJCF][mjXATTRNUM] = {
         {"clock", "*", "4", "name", "cutoff", "noise", "user"},
         {"user", "*", "9", "name", "objtype", "objname", "datatype", "needstage",
             "dim", "cutoff", "noise", "user"},
+    {"tactile", "*", "4", "name", "geom", "mesh", "user"},
         {"plugin", "*", "9", "name", "plugin", "instance", "cutoff", "objtype", "objname", "reftype", "refname",
             "user"},
         {"<"},
@@ -4297,6 +4298,18 @@ void mjXReader::Sensor(XMLElement* section) {
       }
     }
 
+    // tactile sensor
+    if (type == "tactile") {
+      sensor->type = mjSENS_TACTILE;
+      sensor->reftype = mjOBJ_GEOM;
+      ReadAttrTxt(elem, "geom", refname, /*required=*/true);
+
+      // associate the sensor with a mesh
+      sensor->objtype = mjOBJ_MESH;
+      ReadAttrTxt(elem, "mesh", objname, /*required=*/true);
+      mjs_setString(sensor->objname, objname.c_str());
+    }
+
     else if (type == "plugin") {
       sensor->type = mjSENS_PLUGIN;
       OnePlugin(elem, &sensor->plugin);

src/xml/xml_native_reader.h

@@ -101,7 +101,7 @@ class mjXReader : public mjXBase {
 };
 
 // MJCF schema
-#define nMJCF 240
+#define nMJCF 241
 extern const char* MJCF[nMJCF][mjXATTRNUM];
 
 #endif  // MUJOCO_SRC_XML_XML_NATIVE_READER_H_

src/xml/xml_native_writer.cc

@@ -2238,6 +2238,11 @@ void mjXWriter::Sensor(XMLElement* root) {
           WriteAttrKey(elem, "reduce", reduce_map, reduce_sz, sensor->intprm[1], 0);
         }
         break;
+      case mjSENS_TACTILE:
+        elem = InsertEnd(section, "tactile");
+        WriteAttrTxt(elem, "geom", sensor->get_refname());
+        WriteAttrTxt(elem, "mesh", sensor->get_objname());
+        break;
       // global sensors
       case mjSENS_E_POTENTIAL:
         elem = InsertEnd(section, "potential");