[visionegg] Re: screen.clear() requires 40ms....

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Dear Christoph,

My best guess is that OpenGL itself must be taking so long, but this seems very strange. What drivers and hardware are you using? The clear() method is a fairly minimal wrapping of glClear():

def clear(self):
        """Called by Presentation instance. Clear the screen."""

c = self.parameters.bgcolor # Shorthand
if len(c) == 4:
gl.glClearColor(*c)
else:
gl.glClearColor(c[0],c[1],c[2],0.0) # set alpha to 0.0 unless specified
gl.glClear(gl.GL_COLOR_BUFFER_BIT | gl.GL_DEPTH_BUFFER_BIT)

I don't really have any hints at this point, except to make sure you're not doing something silly... Perhaps try with a minimal program that just calls screen.clear() and then add various bits until you find something that makes it start taking so long. (Or maybe it already takes so long with a minimal program?)

Cheers!
Andrew

On Wednesday, Aug 27, 2003, at 20:31 Australia/Adelaide, Christoph Lehmann wrote:

Hi Andrew

the VE-fMRI project goes on..now I can read in by means of a simple GUI (thanks to wxPython) the subject ID and the stimulus-file (where the to be shown stimuli are listed).

One problem: the following code snippet is the essential part yielding a problem:
this code shows me (my_debug_msg), that the screen.clear() routine takes most of the times between 20 and 60ms.
..why this?



while (not pygame.event.peek((QUIT,KEYDOWN))):

    while (not TRIGGER_RECEIVED):
        poll the Lpt...

my_debug_msg.append('before clear.screen [ms]: ' + str(1000 * (VisionEgg.time_func()-start_time)) )

screen.clear()

my_debug_msg.append('after clear screen [ms]: ' + str(1000 * (VisionEgg.time_func()-start_time)) )


viewport.parameters.stimuli = [preloaded_stimulus_list[stim_index]] #update the viewport
viewport.draw()

swap_buffers()


--

I cannot explain it.

Thanks for a hint

christoph
--
p.s.

the preloaded_stimulus_list[stim_index] comes from:

--
# Create a list of TextureStimulus instances, one with each of your texture images.
preloaded_stimulus_list = [] #empty at first
for stim_index in range(num_images): #for all stimuli except the null-event create a texture object
if not photoX[stim_index] == nullevent:
# Read the texture file
texture = Texture(photoX[stim_index])

        # Add to list of TEXTURES
        x = screen.size[0]/2 - texture.size[0]/2
        y = screen.size[1]/2 - texture.size[1]/2

# Load the texture to OpenGL, prepare for display
stimulus = TextureStimulus(texture = texture,size = texture.size, lowerleft=(x,y))
else: #for the nullevent, just append the nullevent-indicator
stimulus = nullevent
# Add to list of stimuli
preloaded_stimulus_list.append( stimulus )

viewport = Viewport( screen=screen)
--


--
Christoph Lehmann <lehmann@xxxxxxxxxxxx>
University Hospital of Clinical Psychiatry

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