Architectural_Design_with_SketchUp

Chapter 5 Rendering in SketchUp
A common method that is often built in to rendering software is to use the desaturated
(grayscale) inverse of the texture image as the bump map. This is a bit of a rough approximation
that can work well, but it is usually a good idea to create higher-quality bump maps in
image-editing software and then use two separate images for the texture and the bump map.
Some rendering software also offers a more advanced technique, called normal mapping.
While bump mapping applies various levels of brightness to any location on a material
depending on the depth information in the bump map, normal mapping modifies light
properties based on a surface’s “normal,” or perpendicular, vector at any given point.
TIP
One method for creating a bump map in image-editing software is to start with a blackand-white
version of the texture image and then invert it. Then use Brightness/Contrast
adjustment to increase the black-and-white contrast in the image. Finally, use a white brush
to remove any unwanted gray or black areas from the image. Don’t forget to save the image
at the same pixel size as the original texture. (See Figure 5.74.)
Figure 5.74: Two different bump maps (left: texture; middle: inverted black-and-white map; right: high-contrast
black-and-white map created in image editor
Displacement
Depending on your rendering software, you may be able to add a displacement map to a
texture as well. This technique goes one step further than bump mapping in that it doesn’t
simply modify light properties but modifies the surface of the object itself. Small or even
larger details can be added to a surface through a displacement map—requiring less initial
modeling and providing a higher level of realism because surface depressions or extrusions
exist as actual geometry.
A good use for a displacement map would again be our brick wall—especially if
larger bricks or round boulders were used for the surface texture. While bump maps fail
to model wall edges properly (they don’t show a mortar recess at the edge, for example),
a displacement map can do this by creating geometry at this location. Other uses are
terrain generation, whereby an entire three-dimensional terrain can be created from a
black-and-white image (typically called a heightfield) in which pixel grayscale corresponds
to altitude values.
195