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Computer Graphics

Rasterization
Rasterization, also known as Scan line rendering, is a process where the outline representation of a 3-D
object is captured, which is usually a triangular mesh. The captured representation is then transformed
into screen space, and projected on the screen. The resulting view is obtained in 2-D geometry as shown
in figure 11.2. This technique is employed in various computer games and other interactive
visualizations since these modern 3-D graphics hardware can rasterize at a fast speed.

Figure 11.2: Rasterization Effect

Now, let us discuss some of the prime differences between ray tracing and rasterization techniques.

Table 11.1 Ray tracing vs. Rasterization

Ray tracing Rasterization

The speed of ray tracing with proper acceleration Rasterization is usually O (n). Thus, it is faster
structures is O (log n) to the number of primitives than Ray tracing.
in the scene. Thus, it is a little bit slower.
Effects such as reflections, shadows, and global These effects find it much harder or even
illumination can be easily added by simply impossible to take effect appropriately through
shooting more rays in smart ways. rasterization.
Usually very low level of memory coherency is Extremely high level of memory coherency can
achieved through ray tracing. be achieved through rasterization.
While ray tracing, the entire picture has to be kept While rasterizing, the entire picture need not to
in memory. be kept in memory as it can be drawn piece by
piece.

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