027 <span class="comment">%      OpenGL        Toggles between the OpenGL and zbuffer renderers.</span>
0028 <span class="comment">%      Params        Creates a dialog box to ask for timing parameters:</span>
0029 <span class="comment">%         Skip  (default: 1 frms) # frames to advance btw frames.</span>
0030 <span class="comment">%         Slow  (default: 0 msec) # msec to pause btw frame advances.</span>
0031 <span class="comment">%         Fs    (default: 1 Hz  ) temporal sampling rate</span>
0032 <s