Sorry about the title, I don’t know how to describe this, therefore I am not sure what to search for to see if this can be done.
I’m working in Adobe Illustrator.
I have the blue shape; I want the purple shape. If it was a raster I would just copy the shape over and over like the green one to get the purple shape, but it seems like there might be something smarter I could do as I’m working with vectors and don’t want unnecessary points in the shape.
I describe it as ‘motion’ because it conceptually seems like I could create the starting shape and the final shape, and something akin to a keyframe animation would fill in the rest.
The actual shapes I’m dealing with are letters, the rectangle is for illustrating the concept only. The letters are plain solid colours just like the rectangle. The angle of ‘motion’ is a simple 45 degrees.
There are several ways of achieving what you want. You could use illustrator’s 3d tools to extrude a shape similar to what you want, then expand the shapes and color as you wish:
Another way is to use a Blend:
A blend combines two shapes in multiple steps, though you can choose for it to be seamless.
To do that, create two shapes, the first, and end ones in your “trail”, and select them.
Open blend options (Object→Blend→Blend Options) and choose a high number of steps
Then create a Blend – Object→Blend→Make or Ctrl/Cmnd+Alt+B