line chart 'smooth' option in extjs 3.4?

Hello,

I am working on creating a line Chart series. The problem is how to make the line 'smooth' like in extjs 4 (not just connecting the points straight)? Do you have any idea how to configure?

Thanks in advance!

Code:

var series = [{
     type:'line',
     smooth: true, // something like this to make the line smooth?
     xField: 'xaxis',
     yField: 'yaxis',
     style: {
        color: 0x15428B
    }
}];

line chart 'smooth' option in extjs 3.4?