[visionegg] Constraining SinGrating2D phase with t0_time_sec_absolute = None

Dear all,

I am trying to constrain the starting phase of a grating. According to an 
earlier suggestion from Andrew, and following the source code for Gratings.py, 
I tried adding a controller for the t0_time_sec_absolute parameter:
  grating_stimulus = SinGrating2D()

  grating_t0_time_sec_absolute_controller = 
EvalStringController(during_go_eval_string='None',
                                            between_go_eval_string='None',
                                            
eval_frequency=VisionEgg.FlowControl.Controller.TRANSITIONS)

  viewport = Viewport( screen=screen, stimuli=[grating_stimulus] )
  p = Presentation(viewports=[viewport],check_events=1)
  p.add_controller(grating_stimulus,'t0_time_sec_absolute', 
grating_t0_time_sec_absolute_controller)
  p.run_forever()
Note that when I used the ConstantController instead of the 
EvalStringController, that is:

     initial_controller=ConstantController(during_go_value=None,...)

I got the following error:
  File "C:\Program 
Files\SurfVision\SurfVisionStimulusSuiteTCP\SurfVisionVisualStimuliSuiteTCP.py",
 line 103, in ?
      eval_frequency=VisionEgg.FlowControl.Controller.TRANSITIONS))
    File "C:\PROGRA~1\Python\lib\site-packages\VisionEgg\FlowControl.py", line 
874, in __init__
      raise ValueError("Must specify during_go_value")
  ValueError: Must specify during_go_value

In any event, with the EvalStringController I get the following error:
  File "C:\Program 
Files\SurfVision\SurfVisionStimulusSuiteTCP\SurfVisionVisualStimuliSuiteTCP.py",
 line 194, in ?
      p.add_controller(grating_stimulus,'t0_time_sec_absolute', 
grating_t0_time_sec_absolute_controller)
    File "C:\PROGRA~1\Python\lib\site-packages\VisionEgg\FlowControl.py", line 
177, in add_controller
      raise TypeError("Attempting to control parameter '%s' of type %s with 
controller that returns type %s"%(
  TypeError: Attempting to control parameter 't0_time_sec_absolute' of type 
Real with controller that returns type None

Thanks very much for any suggestions.

Lyle

Lyle J. Graham
Laboratory of Neurophysics and Physiology, CNRS UMR 8119
www.neurophys.biomedicale.univ-paris5.fr/~graham
UFR Biomédicale de l'Université René Descartes
45 rue des Saint-Pères, 75006 Paris
 
Tel: 33 1 42 86 20 92 (Secrétariat: 33 1 42 86 21 38) Fax: 33 1 49 27 90 62

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