Add optional azimuth and elevation to initial free camera.

- Add `azimuth` and `elevation` to `visual.global`.
- Add `mjv_defaultFreeCamera`.
- Use `mjv_defaultFreeCamera` in `simulate`.

PiperOrigin-RevId: 465505244
Change-Id: I61e60f14a990d4e2d220958adb75c325001978ee

src/engine/engine_io.c

@@ -152,6 +152,8 @@ void mj_defaultVisual(mjVisual* vis) {
   // global
   vis->global.fovy                = 45;
   vis->global.ipd                 = 0.068;
+  vis->global.azimuth             = 90;
+  vis->global.elevation           = -45;
   vis->global.linewidth           = 1.0;
   vis->global.glow                = 0.3;
   vis->global.offwidth            = 640;

src/engine/engine_vis_init.c

@@ -241,6 +241,23 @@ void mjv_defaultCamera(mjvCamera* cam) {
 
 
 
+// set default free camera
+void mjv_defaultFreeCamera(const mjModel* m, mjvCamera* cam) {
+  memset(cam, 0, sizeof(mjvCamera));
+
+  cam->type        = mjCAMERA_FREE;
+  cam->fixedcamid  = -1;
+  cam->trackbodyid = -1;
+  cam->lookat[0]   = m->stat.center[0];
+  cam->lookat[1]   = m->stat.center[1];
+  cam->lookat[2]   = m->stat.center[2];
+  cam->distance    = 1.5 * m->stat.extent;
+  cam->azimuth     = m->vis.global.azimuth;
+  cam->elevation   = m->vis.global.elevation;
+}
+
+
+
 // set default perturbation
 void mjv_defaultPerturb(mjvPerturb* pert) {
   memset(pert, 0, sizeof(mjvPerturb));

src/engine/engine_vis_init.h

@@ -43,6 +43,9 @@ MJAPI void mjv_freeScene(mjvScene* scn);
 // set default visualization options
 MJAPI void mjv_defaultOption(mjvOption* vopt);
 
+// set default free camera
+MJAPI void mjv_defaultFreeCamera(const mjModel* m, mjvCamera* cam);
+
 // set default camera
 MJAPI void mjv_defaultCamera(mjvCamera* cam);