Add MujocoVideoRecorder class

src/jaxsim/mujoco/visualizer.py

@@ -2,8 +2,98 @@
 import pathlib
 from typing import ContextManager
 
+import mediapy as media
 import mujoco as mj
 import mujoco.viewer
+import numpy.typing as npt
+
+
+class MujocoVideoRecorder:
+    """"""
+
+    def __init__(
+        self,
+        model: mj.MjModel,
+        data: mj.MjData,
+        fps: int = 30,
+        width: int | None = None,
+        height: int | None = None,
+        **kwargs,
+    ) -> None:
+        """"""
+
+        width = width if width is not None else model.vis.global_.offwidth
+        height = height if height is not None else model.vis.global_.offheight
+
+        if model.vis.global_.offwidth != width:
+            model.vis.global_.offwidth = width
+
+        if model.vis.global_.offheight != height:
+            model.vis.global_.offheight = height
+
+        self.fps = fps
+        self.frames: list[npt.NDArray] = []
+        self.data: mujoco.MjData | None = None
+        self.model: mujoco.MjModel | None = None
+        self.reset(model=model, data=data)
+
+        self.renderer = mujoco.Renderer(
+            model=self.model,
+            **(dict(width=width, height=height) | kwargs),
+        )
+
+    def reset(
+        self, model: mj.MjModel | None = None, data: mj.MjData | None = None
+    ) -> None:
+        """"""
+
+        self.frames = []
+
+        self.data = data if data is not None else self.data
+        self.model = model if model is not None else self.model
+
+    def render_frame(self, camera_name: str | None = None) -> None:
+        """"""
+
+        mujoco.mj_forward(self.model, self.data)
+        self.renderer.update_scene(data=self.data)  # TODO camera name
+
+        self.frames.append(self.renderer.render())
+
+    def write_video(self, path: pathlib.Path, exist_ok: bool = False) -> None:
+        """"""
+
+        if path.is_dir():
+            raise IsADirectoryError(f"The path '{path}' is a directory.")
+
+        if not exist_ok and path.is_file():
+            raise FileExistsError(f"The file '{path}' already exists.")
+
+        media.write_video(path=path, images=self.frames, fps=self.fps)
+
+    @staticmethod
+    def compute_down_sampling(original_fps: int, target_min_fps: int) -> int:
+        """
+        Return the integer down-sampling factor to reach at least the target fps.
+
+        Args:
+            original_fps: The original fps.
+            target_min_fps: The target minimum fps.
+
+        Returns:
+            The down-sampling factor.
+        """
+
+        down_sampling = 1
+        down_sampling_final = down_sampling
+
+        while original_fps / (down_sampling + 1) >= target_min_fps:
+            down_sampling = down_sampling + 1
+
+            if int(original_fps / down_sampling) == original_fps / down_sampling:
+                down_sampling_final = down_sampling
+
+        return down_sampling_final
 
 
 class MujocoVisualizer: