anychart.onDocumentReady(function() {
chart = anychart.surface()
chart.data(generateData(hyperbolicParaboloid));
var colorScale = anychart.scales.linearColor();
colorScale.colors(['#2bc0e4', '#eAecc6', '#dd2c00']);
chart.colorScale(colorScale);
var colorRange = chart.colorRange();
colorRange.enabled(true);
colorRange.orientation('right');
chart.container('container').draw();
var generateData = function(z_function) {
for (var x = -max_val; x <= max_val; x += step) {
for (var y = -max_val; y <= max_val; y += step) {
output.push([x, y, z_function(x, y)]);
var hyperbolicParaboloid = function(x, y) {
return Math.pow(y,2)-Math.pow(x,2);