Hey,
So I just wanted to start this topic by sharing an idea I came across a while ago. I don't remember where I saw it, maybe it was a youtube video, but I wanted to share it anyway.
For someone like me, who struggles on where to start an environment from imagination, I think it can be really helpful!
Basically, whoever said it, proposed this:
Start by drawing the environment on site or from a picture and if you feel like it, just move on to adding your own shapes and buildings, so that you end up with a mix of reality and fiction.
If you are interested in learning more about sketching on site(urban sketching), I recommend "The Urban Sketcher" by Marc Taro Holmes.
It is an incredibly resourceful book on techniques for seeing and drawing on location that covers several drawing media(pencil, pen and ink, watercolor) and is filled to the brim with - in my opinion - incredible artwork. I think his methods are a great starting point for the above mentioned idea of creating imaginative environments from drawings on site.
