Creating trails using Animation Nodes by delaying the frame of the following polygons

Question

I would like to create a trail of polygons that follows an animated object. Initially, I used the following node tree:

To create the edges that should compose the trail, it produces the following result:

This was created in an old version of AN to make use of the frame option of the Input Transforms node. I then used the method described here to create the polygons.

Modern version of AN don't have the frame option, so I was wondering if there is a solution that would work for Animation Nodes 2.0.

EDIT:

I've transferred his answer to the version of AN I'm using. So I've changed up with some nodes (for AN 2.0 in Blender 2.79b):

Answer 1

You can use F-Curves. F-Curves are functions that describe the value of attributes in Blender. So by evaluating the F-Curves of transformation channels at a certain frame, we can get the transformation of the object at that frame.

First, we create a group that computes the transformation of an object as a matrix and returns it. We will assume that only transformation channels are animated and that they are in order for simplicity.

We then create a loop that iterates over a float list that represents the frames we want to evaluate at.

Then we will replicate a line of matrices based on the output matrices of the loop, where the input frames are arithmetic sequence starting from the current frame. We use the indices data from a Grid Mesh to create the polygons between the replicated matrices.

In this node tree, the step size of the sequence controls the length and direction of the trail:

Blend file for AN 2.1: