Replace functionally opaque Viscous Pause with functionally transparent "Viscous posing mode" toggle.

PiperOrigin-RevId: 947527204
Change-Id: I122a9730fa22ac9e8809762046a89fb0a774d827

python/mujoco/experimental/studio/sim.cc

@@ -32,14 +32,12 @@ PYBIND11_MODULE(sim, m, pybind11::mod_gil_not_used()) {
   py::enum_<StepControl::Status>(m, "StepStatus")
       .value("OK", StepControl::Status::kOk)
       .value("PAUSED", StepControl::Status::kPaused)
-      .value("VISCOUS_PAUSED", StepControl::Status::kViscousPaused)
       .value("AUTO_RESET", StepControl::Status::kAutoReset)
       .value("DIVERGED", StepControl::Status::kDiverged);
 
   py::enum_<StepControl::PauseState>(m, "PauseState")
       .value("UNPAUSED", StepControl::PauseState::kUnpaused)
-      .value("NORMAL_PAUSED", StepControl::PauseState::kNormalPaused)
+      .value("NORMAL_PAUSED", StepControl::PauseState::kNormalPaused);
-      .value("VISCOUS_PAUSED", StepControl::PauseState::kViscousPaused);
 
   py::class_<StepControl>(m, "StepControl")
       .def(py::init<>())

python/mujoco/experimental/studio/studio_app_events.py

@@ -157,15 +157,8 @@ def handle_step_control_keyboard_events(
 
   pressed = imgui.IsKeyChordPressed
 
-  if pressed(int(imgui.Key.Ctrl) | int(imgui.Key.Space)):
+  if pressed(imgui.Key.Space):
-    if step_control.get_pause_state() == sim.PauseState.VISCOUS_PAUSED:
+    if step_control.get_pause_state() == sim.PauseState.UNPAUSED:
-      step_control.set_pause_state(sim.PauseState.UNPAUSED)
-    else:
-      step_control.set_pause_state(sim.PauseState.VISCOUS_PAUSED)
-    return True
-  elif pressed(imgui.Key.Space):
-    pause = step_control.get_pause_state()
-    if pause in (sim.PauseState.VISCOUS_PAUSED, sim.PauseState.UNPAUSED):
       step_control.set_pause_state(sim.PauseState.NORMAL_PAUSED)
     else:
       step_control.set_pause_state(sim.PauseState.UNPAUSED)

src/experimental/platform/sim/step_control.cc

@@ -18,7 +18,6 @@
 #include <chrono>
 #include <cstdlib>
 #include <functional>
-#include <optional>
 #include <ratio>
 
 #include <mujoco/mujoco.h>
@@ -32,31 +31,7 @@ static mjtNum Timer() {
   return Milliseconds(Clock::now() - start).count();
 }
 
-// Updates key viscous pause parameters restores them when done.
-struct ViscousPauseState {
-  ViscousPauseState(mjModel* model) : model(model) {
-    if (model) {
-      mju_copy3(gravity, model->opt.gravity);
-      viscosity = model->opt.viscosity;
-      disableflags = model->opt.disableflags;
-      mju_zero3(model->opt.gravity);
-      model->opt.viscosity = 10;
-      model->opt.disableflags |= mjDSBL_SPRING;
-    }
-  }
 
-  ~ViscousPauseState() {
-    if (model) {
-      mju_copy3(model->opt.gravity, gravity);
-      model->opt.viscosity = viscosity;
-      model->opt.disableflags = disableflags;
-    }
-  }
-  mjModel* model;
-  mjtNum gravity[3];
-  mjtNum viscosity;
-  int disableflags;
-};
 
 
 StepControl::StepControl() { mjcb_time = Timer; }
@@ -100,10 +75,6 @@ StepControl::Status StepControl::Advance(mjModel* m, mjData* d) {
     return Status::kOk;
   }
 
-  std::optional<ViscousPauseState> viscous_pause_state;
-  if (m && pause_state_ == PauseState::kViscousPaused) {
-    viscous_pause_state.emplace(m);
-  }
 
   if (pause_state_ == PauseState::kNormalPaused) {
     // When we eventually unpause, we need to make sure we sync to immediately

src/experimental/platform/sim/step_control.h

@@ -38,9 +38,6 @@ class StepControl {
     // Simulation was not stepped because it is paused.
     kPaused,
 
-    // Simulation is viscously paused (stepping with zero gravity, high
-    // viscosity, and no spring forces).
-    kViscousPaused,
 
     // Simulation diverged with autoreset enabled.
     kAutoReset,
@@ -73,7 +70,7 @@ class StepControl {
   void SetPreStepCallback(StepFn step_fn);
   void SetPostStepCallback(StepFn step_fn);
 
-  enum class PauseState { kUnpaused, kNormalPaused, kViscousPaused };
+  enum class PauseState { kUnpaused, kNormalPaused };
 
   // Sets the pause state of the simulation.
   void SetPauseState(PauseState state);

src/experimental/platform/ux/gui.cc

@@ -511,9 +511,6 @@ void StepControlGui(StepControl* step_control, int& speed_index) {
   make_button(ICON_FA_PAUSE, StepControl::PauseState::kNormalPaused, yellow,
               ImDrawFlags_RoundCornersLeft, "Pause", .3f, 1.6f);
   ImGui::SameLine(0.f, 0.f);
-  make_button(ICON_FA_MAGIC, StepControl::PauseState::kViscousPaused, yellow,
-              ImDrawFlags_RoundCornersNone, "Viscous Pause", .3f, 1.3f);
-  ImGui::SameLine(0.f, 0.f);
   make_button(ICON_FA_PLAY, StepControl::PauseState::kUnpaused, green,
               ImDrawFlags_RoundCornersRight, "", .3f, 1.6f);
 
@@ -983,6 +980,30 @@ void PhysicsGui(mjModel* model, float min_width) {
   }
 
   if (SectionHeader("Physical Parameters")) {
+    // Viscous posing mode toggle: disables gravity and passive springs, adds
+    // viscosity. All changes are directly visible in the parameters below.
+    {
+      constexpr mjtNum kPosingViscosity = 10;
+      bool active = (opt.disableflags & mjDSBL_GRAVITY) &&
+                    (opt.disableflags & mjDSBL_SPRING) &&
+                    (opt.viscosity >= kPosingViscosity);
+      if (ImGui_ButtonToggle("Viscous posing mode", &active)) {
+        if (active) {
+          opt.disableflags |= mjDSBL_GRAVITY;
+          opt.disableflags |= mjDSBL_SPRING;
+          opt.viscosity += kPosingViscosity;
+        } else {
+          opt.disableflags &= ~mjDSBL_GRAVITY;
+          opt.disableflags &= ~mjDSBL_SPRING;
+          opt.viscosity = std::max<mjtNum>(0, opt.viscosity - kPosingViscosity);
+        }
+      }
+      ImGui::SetItemTooltip(
+          "Disable gravity and passive springs,\n"
+          "add viscosity for easier posing.");
+    }
+    ImGui::Spacing();
+
     ImGui_InputN("Gravity", opt.gravity, 3);
     ImGui_InputN("Wind", opt.wind, 3);
     ImGui_InputN("Magnetic", opt.magnetic, 3);

src/experimental/studio/app.cc

@@ -733,16 +733,8 @@ void App::HandleKeyboardEvents() {
         LoadHistory(sim_history_.GetIndex() + 1);
       }
     }
-  } else if (ImGui_IsChordJustPressed(ImGuiMod_Ctrl | ImGuiKey_Space)) {
-    if (step_control_.GetPauseState() == PauseState::kViscousPaused) {
-      step_control_.SetPauseState(PauseState::kUnpaused);
-    } else {
-      step_control_.SetPauseState(PauseState::kViscousPaused);
-    }
   } else if (ImGui_IsChordJustPressed(ImGuiKey_Space)) {
-    if (step_control_.GetPauseState() == PauseState::kViscousPaused) {
+    if (step_control_.GetPauseState() == PauseState::kUnpaused) {
-      step_control_.SetPauseState(PauseState::kNormalPaused);
-    } else if (step_control_.GetPauseState() == PauseState::kUnpaused) {
       step_control_.SetPauseState(PauseState::kNormalPaused);
     } else {
       step_control_.SetPauseState(PauseState::kUnpaused);
@@ -1461,6 +1453,7 @@ void App::TimelineScrubberGui() {
 
   // Advance layout cursor past this row.
   ImGui::SetCursorScreenPos(ImVec2(cursor.x, cursor.y + total_h));
+  ImGui::Dummy(ImVec2(0.0f, 0.0f));
 }
 
 void App::ModelOptionsGui() {
@@ -2178,8 +2171,8 @@ void App::ToolBarGui() {
     ImGui::TableSetupColumn("", ImGuiTableColumnFlags_WidthFixed, right_width);
 
     ImGui::TableNextColumn();
-    ImGui::SetCursorPosX(ImGui::GetCursorPosX() +
+    ImGui::Dummy(ImVec2(ImGui::GetStyle().WindowPadding.x, 0.0f));
-                         ImGui::GetStyle().WindowPadding.x);
+    ImGui::SameLine(0.0f, 0.0f);
 
     const float btn_size = ImGui::GetFrameHeight();
     const ImVec2 square_size(btn_size, btn_size);
@@ -2200,7 +2193,7 @@ void App::ToolBarGui() {
     }
     ImGui::SetItemTooltip("%s", "Reset");
 
-    // Combined (Normal Pause, Viscous Pause, Play) widget and Speed selection.
+    // Combined (Pause, Play) widget and Speed selection.
     ImGui::SameLine(0, separator_width);
     platform::StepControlGui(&step_control_, tmp_.speed_index);
 
@@ -2228,9 +2221,6 @@ void App::StatusBarGui() {
 
     if (!has_model()) {
       ImGui::Text("No model loaded");
-    } else if (step_control_.GetPauseState() == PauseState::kViscousPaused) {
-      ImGui::Text("Viscous Pause");
-      ImGui::SetItemTooltip("Zero gravity, high viscosity, no spring forces");
     } else if (step_control_.GetPauseState() == PauseState::kNormalPaused) {
       ImGui::Text("Paused");
     } else {