track

aximate allows you to "track" a point by a line on its way through the movie. Consider this example:
    $p1 = line({"foot" => [[]],
		"head" => [[20,-100],[200,-100]]},
		{"foot" => ['-100+250*$t**2',
				   '40*sin(5*cos(4*pi*$t)*$t)']});
    track("c1",{%{$p1},
		"color" => "Red",
		"parameter" => "foot"});
Notice that the line has some kinks. That's because it is actually a polygon that connects the individual points corresponding to each image of the movie. You may smoothen the line by simply setting the parameter steps to a larger value in setparams. However, this creates a longer and bigger movie.
In certain cases, you may choose to draw the curve using axodraw's way by connecting the points by second or third order polynomials with proper boundary conditions. This is controlled by the parameter curve:
    $p1 = line({"foot" => [[]],
		"head" => [[20,-100],[200,-100]]},
		{"foot" => ['-100+250*$t**2',
				   '40*sin(5*cos(4*pi*$t)*$t)']});
    track("c1",{%{$p1},"curve" => "axocurve",
		"color" => "Red",>
		"parameter" => "foot"});>

Note that, due to the restrictions of axocurve, this option only works if the horizontal movement is monotonous, i.e., if the point moves either forward or backward throughout the movie.
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