2d transform is a very powerful modifier. It seems very simple, but playing with the right parameters (frame and wrap modes) and masks makes it one of the most useful and versatile 2D distortion effect.
2d transform takes the input image and places it somewhere in the output image. If the output is not fully filled, it completes the image depending on its Wrap Modes
Here are three examples of 2d transform with different parameters:
Scale down image
Rotate with Mirrored Repeat
Perspective with Horizontal Repeat
The last example (Perspective with Horizontal Repeat) is obtained with the following parameters:
In order to edit each four points defining the perspective, put the Frame
Placement defined by a quad using perspective interpolation
in the visualizer (red circle in the image above).
A very interesting aspect of distortion modifiers is the way they interact with
Define a 2D Mask applicable on any 2D Renderer or 2D Modifier
In the following example, a swirl effect is obtained by having a 2d transform with rotation at 45° and a radial mask with a feather:
2D Transform with rotation plus Radial TextureMask with feather