4.9.6.1 delta - delta( x )

The delta function returns the current frames value minus the last frames value. The function is thus a shortcut for this procedure:

offset = channel_value - channel_value[ frame - 1 ];

This is the same as

offset = delta( channel_value );

Since the function needs to be able to index its argument you can only use the function with indexable arguments (channels).

Note: This function will force Xpressionist to look for the frame before the current frame. If Xpressionist executes on frame 0 it will give an error since it looks for a frame prior to frame 0 which is not existent. You need to set the start frame of execution for Xpressionist to frame 1 in the execution options in the preferences of Xpressionist for this function to work as expected.