Answer: This is a picture entitled, the Ruin's of Gallego Flour Mills, Richmond. It records an event and exists as an allegory of the costs of the civil war. This was created ad a document the hardships of the civil war, but its purpose has also become to commemorate the civil war so that we ca remember the people who suffered and the reasons why the war occurred.
Op art designs are usually geometric patterns used to create an illusion. Im not really sure what you mean by "how say two artists that drow these things"