fleeting patterns

The patterns of lights made me stop my car. I knew the shapes wouldn't last long, but didn't want to pass on this design either. I tried to mark down where the light patches were before proceeding my usual way. About an hour later the patterns were completely different and I tried to work from memory and where I marked them before, but it didn't feel authentic. I had to retouch it more back at home based on the photo I took. I believe in order for light and shadow to be convincing they need to be based on reality and not pure imagination.

Across from McGill park - oil on panel - 9" x 12"