HOW Do I make realistic shadows on top of an Image?

Joel Wrigglesworth, UK

I played the game Myst in the mid ‘90s, and like much of the world was completely fascinated and immersed with the amazing 3D graphics, so I landed myself a free copy of Bryce 2.0 at a software and hardware tradeshow. I still remember making my first render, a simple island nested in a water plane. It was a case of a few clicks, picking a water texture, adding some sunlight and hitting render. It was an amazing feeling to be able to create such realistic visuals, whole worlds even, with very little effort. I was hooked!

Back then, my wife always said she didn’t like the unrealistic horizon line in my Bryce renders, nor how fake the shadows always looked. I frequently found myself trying to compensate by hiding the horizon with objects and by editing the shadows in other photo editing software. Anyone who used Bryce back then knows exactly what I am talking about.

I remember wishing there was an easy way to composite 3D objects and their shadows on to a 2D image or background, and had I been a software developer, I probably would have created a plug-in that solved the issue and made millions. Instead, I just waited around for others to come up with a solution.

Fortunately, in modern times, casting realistic shadows on top of an image is fairly easy. In my image titled Pluvia Mundi (which is Latin for Rain World), I used Cinema 4D to set up and render convincing 3D objects and shadows over a 2D image that I use for the background. Although the process is pretty straightforward, sometimes getting the shadows to cast and feel realistic can be a bit tricky.

In this article, I cover the four steps I use to get everything set up using a still photo as the background, while casting shadows from 3D objects onto the floor.

The background image was obtained from the US Library of Congress

(www.bit.ly/picture-resource). I felt it had the perfect mood for what I was trying to achieve, and it also saved me the trouble of having to model and texture something similar for the background. It also had no known restrictions on use or publication. If you are lucky enough to have the latest release of Cinema 4D, there is some exciting news. Maxon has just rendered everything I have written in the steps below obsolete. In Cinema 4D R18, you can easily integrate 3D objects into photos or live footage with the new Shadow Catcher shader. You simply apply the shader to geometry that roughly matches the footage or background image and composite the rendered result using an alpha that includes shadows.

For the rest of us that are still using the older version of Cinema 4D (and why not?), my method works like a charm. Hope this solution helps!