Archive for July, 2010

The Role Of 3D Geometry On Man-Made Materials

A number of physical features in the geometry can contribute to give the illusion of grunge materials, among them are:

Surface dents and bulges
Chips and cracks
Wear and tear on edges and corners
Folds and wrinkles

While it is a good idea to use bump and opacity maps to create the illusion of geometry as often as possible, it is sometimes necessary to build these imperfections into the mesh geometry. You can use mesh modifiers such as Noise and Mesh smooth to distort the edges of objects, or use Boolean operations to create major cracks and crevices, for example.

Such major features are just too large to be handled well by the bump and opacity maps. Your 3D application offers some great tools to get you on your way to roughing up your mesh objects, such as:

Extended Primitives for chamfering and filleting edges.
Mesh smooth modifier for rounding edges.
Relax and Spherify modifier for rounding objects.
Ripple and Wave modifiers and Space warps for rippling surfaces.
Noise modifier for random surface perturbations.
Displace modifier for perturbations based on image luminance.
Affect Region modifier for dents and bulges.
FFD modifiers and Space warps for molding surfaces.

Not all material manipulations have to be on the negative side. You can greatly enhance the look of highly reflective materials by adding objects in the scene-not to be seen directly, but to be reflected. Simply keep them out of the line of sight.

Adding Grunge to Materials: Once you have your mesh object roughed up at the geometry level, you need to add the fine detail that makes the surface look real. Some of the grunge might be bold whereas some other might be subtle. It is very important to add at least one of the effects listed here to all materials, however, to avoid the homogeneous plastic look. Several possibilities for grunge are:

Smudges and discoloration
Scratches and weathering
Puddles and variations in reflectivity
Dust and grime.