starting phase

Lindsey Glickfeld's Avatar

Lindsey Glickfeld

05 Oct, 2020 09:21 PM

Hi Chris,

I've come upon another experimental problem with the definition of the starting phase being set at the edge rather than the center of the grating. In this condition, a plaid with components moving at 0 and 90 has a different alignment than a plaid with components moving at 180 and 270 (if you just present a static plaid that swaps directions, the pattern changes). Correcting for this will probably depend on both the spatial frequency and the diameter of the grating, but it's not obvious to me how to deal with it. Do you know the best way to handle this for arbitrary pairs of gratings at 90 deg separation?

Either way, given that this has come up a couple times, it would be really nice to have an option to choose whether you want to use the edge vs center for determining the starting phase. Is this something that you could integrate in future versions?

Thanks,
Lindsey.

  1. Support Staff 1 Posted by Christopher Sta... on 05 Oct, 2020 09:34 PM

    Christopher Stawarz's Avatar

    Hi Lindsey,

    I've come upon another experimental problem with the definition of the starting phase being set at the edge rather than the center of the grating. In this condition, a plaid with components moving at 0 and 90 has a different alignment than a plaid with components moving at 180 and 270 (if you just present a static plaid that swaps directions, the pattern changes). Correcting for this will probably depend on both the spatial frequency and the diameter of the grating, but it's not obvious to me how to deal with it. Do you know the best way to handle this for arbitrary pairs of gratings at 90 deg separation?

    The starting phase correction that I suggested already depends on both the spatial frequency and the diameter. When I add this correction to both gratings in the plaid example I sent you, set the grating speeds to zero, and add code to switch between 0/90 and 180/270, I get a static dot pattern. (See the attached example.)

    If I misunderstood the scenario you're describing, can you send me an example that demonstrates the issue?

    Either way, given that this has come up a couple times, it would be really nice to have an option to choose whether you want to use the edge vs center for determining the starting phase. Is this something that you could integrate in future versions?

    Yes, definitely. I will try to get that in the nightly build soon.

    Cheers,
    Chris

  2. 2 Posted by Lindsey Glickfe... on 05 Oct, 2020 09:40 PM

    Lindsey Glickfeld's Avatar

    Hi Chris,
    Oops- I didn't realize that the correction that you had sent me before
    would solve this as well- but of course.
    I had just tested it using the old example code that you had sent before
    and hadn't added the correction to it (or to any of my other experiments
    using plaids).
    I'll do that now (and check to make sure it works in my hands)- thanks!
    Lindsey.

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