Rendering a realistic drum requires getting down and dirty.
"In order for something like a drum head to look realistic, it needs to look less than perfect," reveals David Crognale, Animusic's digital artist. "It should look like it has been hit repeatedly. It needs to be given the appearance of being aged, used, and worn.
"First, it is helpful to look at the real thing. This may seem obvious but is something easy to forget: find references of the thing that you are texturing. It can be the actual object, if that is practical, or photos or footage. Anything that shows how a thing looks in real life."
The key concept, Crognale continues, is to mix things up, combining or layering a number of different texture maps to create a more realistic surface. He typically uses two or more different texture maps for the various characteristics of his intended visual result.
"The main effect is the hit marks, usually centered on the drum head," he explains."The location and number of hit marks are directly related to where the sticks or balls impact the drum. If you really want to go wild, you can also look at how many times a particular drum is hit and adjust the intensity of the hit marks in proportion. The hit-mark map is sometimes hand-painted in a program like Photoshop or Painter using a pressure-sensitive tablet. Another approach I may use is to make a procedural map with radial gradients and some built-in noise." (See Figure 1.)
Figure 1: Hit-mark image
Another characteristic element Crognale layers on an Animusic drum head is overall wear and tear. He sometimes calls this element a dirt and grime map. (See Figure 2.) To his localized hit-mark map, he will add a subtle texture map containing random smudges and scratches. These marks are either hand-painted or taken from a texture map collection. Crognale says this can also be accomplished by combining some procedural noise maps, but warns that can look fake if not done carefully.
Figure 2: Hand-painted smudges and scratches increase realism.
"An important concept here is to use restraint," he continues. "You don't want the hit and smudge maps to draw too much attention to themselves, but to blend in with the rest of the scene and level of detail and other intentional imperfections. Another concept is to not limit the maps to the color channel of the material. I tend to apply some variation of the color map to the specular—that is, how much shine there is—and to the glossiness, or in other words, how sharp the highlights are."
Figure 3: The mixed image, mapped to a 3D surface
Figure 4: Finally, the drum head is rendered.
Crognale sometimes applies a bit of digital dirt to the bump-map channel as well. "The idea here is to add variations to the highlights on the drum head's surface," he explains. "Again, this is to break up that computer graphics perfection."
Randy Alberts is an author, musician, and photographer who lives on Lummi Island, Washington.
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