Page 203 - DCAP504_Computer Graphics

Computer Graphics

six square regions of a single texture. Some of the higher mapping techniques like pyramid
mapping and octahedron mapping are also used in the environmental mapping technique.
3. Bump Mapping: Bump mapping alters the normal vectors during the process of rendering through
emulation. The faces of various objects do not have the same color always. Random texturing can
be depicted by accumulating the random deviations and calculating the surface normal as done in
Phong shading. In the bump mapping method, the location of the surface is not changed, but the
artificial change of orientation scatters light in all possible directions making the object appear as
though it is from a series of bumpy surface. This method is known as bump mapping. The
following figure 13.5 depicts the bumpy surface, pertaining to bump mapping.

Figure 13.5: Bump Mapping

Source: http://www.cs.kent.edu/~farrell/cg05/lectures/cg22.pdf
Unwrapping
Before texturing any model, it is required to be mapped and unwrapped so that the lines and points of
the image are clearly viewable without overlapping. Thus, unwrapping is the method of preparing a
model for texturing.
Let us consider the cuneiform clay tablets of Mesopotamia. They are famous for the inscriptions which
were made millions of years ago. To understand these writings, it is required to visualize the cuneiform
writings by deciphering. This is done to ensure proper reproduction of the tablets on paper.
Photographs were not adequate to visualize the tablets due to the following two reasons:
1. Insufficient single view point due to text wraps around the sides of the tablet.
2. Raking lights illuminating only a part of the textual information (this leaves the other texts either
shadowed or invisible due to the obscured features on the tablet or when the tablets are nearly
aligned with the lighting direction).

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