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I’d hoped to gain more insight from reading Jeremy Burns chapter on Decals and Dirt, but found that I had already been using what he refers to as Decals in my projects. In the example robot image below, I had already applied decals (stickers) to my robot, however, what I hadn’t done was added dirt.
In this example I’ve probably gone a little over the top with the dirt but it helps to illustrate the point I’m making.
When I showed the animated version of this robot to a fellow artist, he immediately noticed the lack of movement in the robot’s hands and how clean the robot looked in comparison to the background. Although the film noise/grain and motion blur that had been added were helping to blend the two media together, it seemed the texture on the surface of the robot’s skin, was too clean and shiny to begin with.
In the example above, I’ve used Ambient Occlusion (a tool for finding edges between two surfaces and is often used to emphasize shadows) to create the dirt which in my opinion is a inaccurate way to achieve the effect. When creating dirt with a photorealistc effect, you should paint dirt onto a model by hand. Burns (p229) correctly states that you should “choose dirt maps that add specific, motivated detail to your objects. Think through the story behind all of the stains and imperfections on a surface – something has to cause any dirt, scratches, or stains that you would see”.
In the example above, dust would have fallen and settled onto the robot from above, this would mean that the robot’s shoulders, head, bridge of it’s nose and chest would probably have accumulated the most dust. Similarly, water dripping from the ceiling would have created vertical streaks running down the robot’s body.
Painting in these extra details will require considerable time but it’s this attention to details that will eventually sell the illusion of photorealism.