From 4e10f20be662a25c946d8b4638026c3dbafb04b9 Mon Sep 17 00:00:00 2001
From: Yuval Tassa <tassa@google.com>
Date: Mon, 15 Jun 2026 06:29:02 -0700
Subject: [PATCH] Fix set_to_muscle() to accept tuple arguments.

Correct argument types for timeconst and range parameters in pybind11
python bindings from C arrays to std::array.

Fixes #3282, #3282, #3318

Thanks to @Abzaek for original PRs

PiperOrigin-RevId: 932423401
Change-Id: Ic30ba076913693f5c0e545789690e8b0fa444390
---
 python/mujoco/specs.cc      | 20 +++++++++++---------
 python/mujoco/specs_test.py | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 9 deletions(-)

diff --git a/python/mujoco/specs.cc b/python/mujoco/specs.cc
index 4d5784cb..8bc0d00d 100644
--- a/python/mujoco/specs.cc
+++ b/python/mujoco/specs.cc
@@ -1577,20 +1577,22 @@ PYBIND11_MODULE(_specs, m) {
       py::arg("diameter") = -1);
   mjsActuator.def(
       "set_to_muscle",
-      [](raw::MjsActuator* self, double timeconst[2], double tausmooth,
-         double range[2], double force, double scale, double lmin, double lmax,
-         double vmax, double fpmax, double fvmax) {
+      [](raw::MjsActuator* self, std::array<double, 2> timeconst,
+         double tausmooth, std::array<double, 2> range, double force,
+         double scale, double lmin, double lmax, double vmax, double fpmax,
+         double fvmax) {
         std::string err =
-            mjs_setToMuscle(self, timeconst, tausmooth, range, force, scale,
-                            lmin, lmax, vmax, fpmax, fvmax);
+            mjs_setToMuscle(self, timeconst.data(), tausmooth, range.data(),
+                            force, scale, lmin, lmax, vmax, fpmax, fvmax);
         if (!err.empty()) {
           throw pybind11::value_error(err);
         }
       },
-      py::arg("timeconst") = -1, py::arg("tausmooth"),
-      py::arg("range") = std::array<double, 2>{-1, -1}, py::arg("force") = -1,
-      py::arg("scale") = -1, py::arg("lmin") = -1, py::arg("lmax") = -1,
-      py::arg("vmax") = -1, py::arg("fpmax") = -1, py::arg("fvmax") = -1);
+      py::arg("timeconst") = std::array<double, 2>{-1, -1},
+      py::arg("tausmooth"), py::arg("range") = std::array<double, 2>{-1, -1},
+      py::arg("force") = -1, py::arg("scale") = -1, py::arg("lmin") = -1,
+      py::arg("lmax") = -1, py::arg("vmax") = -1, py::arg("fpmax") = -1,
+      py::arg("fvmax") = -1);
   mjsActuator.def(
       "set_to_adhesion",
       [](raw::MjsActuator* self, double gain) {
diff --git a/python/mujoco/specs_test.py b/python/mujoco/specs_test.py
index 047584a3..17b803c8 100644
--- a/python/mujoco/specs_test.py
+++ b/python/mujoco/specs_test.py
@@ -1602,6 +1602,38 @@ class SpecsTest(absltest.TestCase):
     self.assertEqual(actuator.gaintype, mujoco.mjtGain.mjGAIN_DCMOTOR)
     self.assertEqual(actuator.biastype, mujoco.mjtBias.mjBIAS_DCMOTOR)
 
+    actuator = spec.add_actuator()
+    actuator.set_to_muscle(tausmooth=0.1)
+    self.assertEqual(actuator.dyntype, mujoco.mjtDyn.mjDYN_MUSCLE)
+    self.assertEqual(actuator.gaintype, mujoco.mjtGain.mjGAIN_MUSCLE)
+    self.assertEqual(actuator.biastype, mujoco.mjtBias.mjBIAS_MUSCLE)
+    self.assertEqual(actuator.dynprm[2], 0.1)
+
+    actuator.set_to_muscle(
+        timeconst=[0.02, 0.05],
+        tausmooth=0.2,
+        range=[0.8, 1.2],
+        force=5.0,
+        scale=250.0,
+        lmin=0.6,
+        lmax=1.7,
+        vmax=1.8,
+        fpmax=1.4,
+        fvmax=1.5,
+    )
+    self.assertEqual(actuator.dynprm[0], 0.02)
+    self.assertEqual(actuator.dynprm[1], 0.05)
+    self.assertEqual(actuator.dynprm[2], 0.2)
+    self.assertEqual(actuator.gainprm[0], 0.8)
+    self.assertEqual(actuator.gainprm[1], 1.2)
+    self.assertEqual(actuator.gainprm[2], 5.0)
+    self.assertEqual(actuator.gainprm[3], 250.0)
+    self.assertEqual(actuator.gainprm[4], 0.6)
+    self.assertEqual(actuator.gainprm[5], 1.7)
+    self.assertEqual(actuator.gainprm[6], 1.8)
+    self.assertEqual(actuator.gainprm[7], 1.4)
+    self.assertEqual(actuator.gainprm[8], 1.5)
+
   def test_bad_contact_sensor(self):
     test_cases = [
         dict(