Add control values to keyframes.

- Add basic test for keyframes.
- Add missing documentation for keyframe mocap positions and quaternions.

PiperOrigin-RevId: 459021649
Change-Id: I91cf7ecbddc6262e8c72a868eeb82d627f389fb3

src/engine/engine_io.c

@@ -1016,6 +1016,7 @@ void mj_resetDataKeyframe(const mjModel* m, mjData* d, int key) {
     mju_copy(d->act,  m->key_act+ key*m->na, m->na);
     mju_copy(d->mocap_pos,  m->key_mpos+key*3*m->nmocap, 3*m->nmocap);
     mju_copy(d->mocap_quat, m->key_mquat+key*4*m->nmocap, 4*m->nmocap);
+    mju_copy(d->ctrl, m->key_ctrl+key*m->nu, m->nu);
   }
 }
 

src/engine/engine_print.c

@@ -592,7 +592,7 @@ void mj_printFormattedModel(const mjModel* m, const char* filename, const char*
         k = 2;
       }
 
-    // print if nozero
+    // print if nonzero
     if (k==2) {
       fprintf(fp, "key_qvel%d   ", i);
       for (int j=0; j<m->nv; j++) {
@@ -665,6 +665,24 @@ void mj_printFormattedModel(const mjModel* m, const char* filename, const char*
       fprintf(fp, "\n");
     }
 
+    // check ctrl for nonzero
+    for (int j=0; j<m->nu; j++) {
+      if (m->key_ctrl[i*m->nu + j]) {
+        k = 6;
+        break;
+      }
+    }
+
+    // print if nonzero
+    if (k==6) {
+      fprintf(fp, "key_ctrl%d   ", i);
+      for (int j=0; j<m->nu; j++) {
+        fprintf(fp, float_format, m->key_ctrl[i*m->nu + j]);
+      }
+      fprintf(fp, "\n");
+    }
+
+
     // new line if any data was written
     if (k) {
       fprintf(fp, "\n");