Continuous animations

[thoppe]

Multiple people expressed interest in creating animations that do not have a fixed time schedule, but rather run with a generator. I envision an Artist generator that takes input continuously and keeps rendering until broken by the user. cc @ehaengel

[apsistech]

What kind of frame rates do you think CV2 could support? For example do you think it could plot 1024 points on a graph at 10 fps?

It'd be kind of cool if the Artist generator could fail safely. Say there's no data available when it polls for input, there could be a timeout and if the timeout hits then it could assume a default image.

That leads to another question I had, does the Artist generator grab data or does it wait for data? Yet a third possibility is that the Artist generator is a class object, and if you want to use it you create a derived child class that somehow has a mechanism to get data itself.

[thoppe]

I think if you do it properly, you could easily get 10fps. CV2 can plot and annotate that much coming from a live webcam. I'll mock up a simple Artist and Canvas method that shows random data and we can go from there.

[thoppe]

Whoa, that was super easy to write! Check out the branch live_artist and the example. It generates this little image that live displays the frame rate.

With an image of (800x400) I get 27 fps, and twice that (1600,800) I get 7 fps which is almost perfect scaling w.r.t. the square (or proportional to the number of pixels). This write to every pixel, so with a single line plot it could probably be much faster.

[thoppe]

@apsistech if you want to play with this, you could come up with a more complicated Artist that computes in the background while waiting for a poll. Or you could implement the poll/wait/blank method that gets beyond a simple block (that's what's done now). Honestly, this is all the live animation is now:

class LiveAnimation(Animation):

    def show(self, delay=1):
        while True:
            img = self.render(0)
            self.has_rendered[0] = False
            img.show(delay=delay)

[thoppe]

Also, without the full pixel write, I get about 50fps just writing to text and blank rectangle to the screen with 800x400 resolution.

[apsistech]

Oh cool, that's great to hear, I'll git clone your repo and try messing around myself soon!