javascript - Manipulating the slider - the circle disappears -

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javascript - Manipulating the slider - the circle disappears -

manipulating slider until end, circle represents star disappears or different motion. see: jsfiddle.net/nxnxj/13 unlike this: astro.unl.edu/naap/hr/animations/hrexplorer.html

can help me?? thanks

when supply big luminosity, you're rendering circle millions of pixels tall. broswer might not render because it's big. however, interested in little piece of big circle - namely, bit fits in tiny window. @ point, doesn't create sense increment size of circle, since can't observe alter in curvature of circle - looks straight vertical line.

this apparent verticality occurs around when x^2 + y^2 = r^2, r radius of star, y half height of window, , x r-1. solve r in terms of y, , get

function maximumnecessaryradius(windowheight){ y = windowheight / 2; maxradius = (y*y - 1)/2; homecoming math.round(maxradius); }

when resizing star, check create sure radius doesn't exceed maximum necessary radius. rendering larger overkill.

example implementation

javascript browser slider

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