Add body/simple attribute to control simple body optimization.

PiperOrigin-RevId: 942164766
Change-Id: I1e83bb99b6a1955917eb9b2e9bed0dc7b8e6a161

src/xml/xml_native_reader.cc

@@ -335,9 +335,8 @@ std::vector<const char*> MJCF[nMJCF] = {
         {">"},
         {"model", "*", "name", "file", "content_type"},
     {">"},
-
-    {"body", "R", "name", "childclass", "pos", "quat", "mocap",
-        "axisangle", "xyaxes", "zaxis", "euler", "gravcomp", "sleep", "user"},
+    {"body", "R", "name", "childclass", "pos", "quat", "mocap", "axisangle",
+        "xyaxes", "zaxis", "euler", "gravcomp", "sleep", "simple", "user"},
     {"<"},
         {"inertial", "?", "pos", "quat", "mass", "diaginertia",
             "axisangle", "xyaxes", "zaxis", "euler", "fullinertia"},
@@ -644,6 +643,13 @@ const mjMap TFAuto_map[3] = {
 };
 
 
+// FAuto type
+const mjMap FAuto_map[2] = {
+  {"false",   0},
+  {"auto",    1}
+};
+
+
 // body sleep type
 const int bodysleep_sz = 4;
 const mjMap bodysleep_map[bodysleep_sz] = {
@@ -3926,6 +3932,9 @@ void mjXReader::Body(XMLElement* section, mjsBody* body, mjsFrame* frame,
       if (MapValue(elem, "sleep", &n, bodysleep_map, bodysleep_sz)) {
         child->sleep = (mjtSleepPolicy) n;
       }
+      if (MapValue(elem, "simple", &n, FAuto_map, 2)) {
+        child->simple = (mjtByte) n;
+      }
 
       // read userdata
       std::vector<double> userdata;