Add output attribute to camera elements.

This attribute allows specifying the intended output types (e.g., RGB, depth, normal) for each camera in the XML. The output types are stored as bit flags in `mjModel`.

PiperOrigin-RevId: 853316261
Change-Id: I1ad2e94102593cf402756f8f4c80509371ca86d2

doc/XMLreference.rst

@@ -2988,6 +2988,20 @@ and the +Y axis points up. Thus the frame position and orientation are the key a
    location to save the required resolution. Setting either value larger than 1
    enables frustum visualization when the :ref:`mjVIS_CAMERA<mjtVisFlag>` visualization flag is active.
 
+.. _body-camera-output:
+
+:at:`output`: :at-val:`[rgb, depth, distance, normal, segmentation], "rgb"`
+   Types of output images supported by the camera.
+
+   - :at-val:`rgb`: RGB image.
+   - :at-val:`depth`: Depth image (distance from camera plane).
+   - :at-val:`distance`: Distance image (distance from camera origin).
+   - :at-val:`normal`: Surface normal image.
+   - :at-val:`segmentation`: Segmentation image.
+
+   This attribute is not used for rendering, but serves as a convenient location to save the output types supported by
+   the camera. The :at:`output` attribute can contain multiple types, e.g. :at-val:`"rgb normal"`.
+
 .. _body-camera-sensorsize:
 
 :at:`sensorsize`: :at-val:`real(2), "0 0"`
@@ -8715,6 +8729,8 @@ if omitted.
 
 .. _default-camera-resolution:
 
+.. _default-camera-output:
+
 .. _default-camera-ipd:
 
 .. _default-camera-pos: