Add realtime parameter to visual global.

PiperOrigin-RevId: 478775714
Change-Id: Ic2d178a5c57d298d005215219ce8470392c4651b

doc/APIreference.rst

@@ -1237,6 +1237,7 @@ mjVisual
            float ipd;                  // inter-pupilary distance for free camera
            float linewidth;            // line width for wireframe and ray rendering
            float glow;                 // glow coefficient for selected body
+           float realtime;             // initial real-time factor (1: real time)
            int offwidth;               // width of offscreen buffer
            int offheight;              // height of offscreen buffer
        } global;

doc/XMLreference.rst

@@ -592,6 +592,9 @@ is effectively a miscellaneous subsection.
 :at:`glow`: :at-val:`real, "0.3"`
    The value of this attribute is added to the emission coefficient of all geoms attached to the selected body. As a
    result, the selected body appears to glow.
+:at:`realtime`: :at-val:`real, "1"`
+   This value sets the initial real-time factor of the model, when loaded in `simulate`. 1: real time. Less than 1:
+   slower than real time. Must be greater than 0.
 :at:`offwidth`: :at-val:`int, "640"`
    This and the next attribute specify the size in pixels of the off-screen OpenGL rendering buffer. This attribute
    specifies the width of the buffer. The size of this buffer can also be adjusted at runtime, but it is usually more

doc/changelog.rst

@@ -50,6 +50,8 @@ General
 - Added :at:`assetdir` compiler option, which sets the values of both :at:`meshdir` and :at:`texturedir`. Values in
   the latter attributes take precedence over :at:`assetdir`.
 
+- Added :at:`realtime` option to :ref:`visual` for starting a simulation at a slower speed.
+
 Python bindings
 ^^^^^^^^^^^^^^^