Add missing face attribute to the XML schema.

PiperOrigin-RevId: 561330536
Change-Id: I693fc5228591e4a26ea0749435a6ce9869afd457

src/user/user_composite.cc

@@ -236,7 +236,7 @@ bool mjCComposite::Make(mjCModel* model, mjCBody* body, char* error, int error_s
   }
 
   // check spacing
-  if (type==mjCOMPTYPE_GRID || type==mjCOMPTYPE_PARTICLE) {
+  if (type==mjCOMPTYPE_GRID || (type==mjCOMPTYPE_PARTICLE && uservert.empty())) {
     if (spacing < mju_max(def[0].geom.size[0],
                   mju_max(def[0].geom.size[1], def[0].geom.size[2]))) {
       return comperr(error, "Spacing must be larger than geometry size",
@@ -2192,7 +2192,7 @@ void mjCComposite::MakeSkin3(mjCModel* model) {
   }
 
   // box
-  if (type==mjCOMPTYPE_BOX || type==mjCOMPTYPE_PARTICLE) {
+  else if (type==mjCOMPTYPE_BOX || type==mjCOMPTYPE_PARTICLE) {
     // z-faces
     MakeSkin3Box(skin, count[0], count[1], 1, vcnt, "%sB%d_%d_0");
     fmt = "%sB%d_%d_" + string(cnt2);

src/xml/xml_native_reader.cc

@@ -270,8 +270,8 @@ static const char* MJCF[nMJCF][mjXATTRNUM] = {
         {"light", "*", "15", "name", "class", "directional", "castshadow", "active",
             "pos", "dir", "attenuation", "cutoff", "exponent", "ambient", "diffuse", "specular",
             "mode", "target"},
-        {"composite", "*", "12", "prefix", "type", "count", "spacing", "offset",
-            "flatinertia", "solrefsmooth", "solimpsmooth", "vertex",
+        {"composite", "*", "13", "prefix", "type", "count", "spacing", "offset",
+            "flatinertia", "solrefsmooth", "solimpsmooth", "vertex", "face",
             "initial", "curve", "size"},
         {"<"},
             {"plugin", "*", "2", "plugin", "instance"},
@@ -1943,6 +1943,9 @@ void mjXReader::OneComposite(XMLElement* elem, mjCBody* pbody, mjCDef* def) {
     String2Vector(text, comp.uservert);
   }
 
+  // shell
+  ReadAttrTxt(elem, "face", comp.userface);
+
   // process curve string
   std::istringstream iss(curves);
   int i = 0;