anvas_rect = canvas.getBoundingClientRect();
		points_for_approximation[approximation_i] = [e.clientX - canvas_rect.left, e.clientY - canvas_rect.top];
		draw_canvas("approximation_canvas");
	}, false);

	draw_canvas("approximation_canvas");
}

var interpolation_i = 0;
function init_interpolation_canvas(){
	var canvas = document.getElementById("interpolation_canvas");
	canvas.addEventListener('pointerdown', function(e){
		canvas_rect = canvas.getBoundingClientRect();
		const xy = [e.clientX - canvas_rect.le