The Importance of Resolution in CG - An Introduction to Computer Graphics for Artists - page 94

Fig. 7.3 The object group on the left contains 6,032 triangles. The low-res version on the right has
244. Both images display the same number of parts, but one has a much lower level of curve detail

Curve detail is the number of polygonal edge segments used to represent an arc
of a given length. A 1 m diameter 180° arc represented by two edges has a very low
level of detail. If it has a hundred edges, it has a high level of detail (Fig. 7.3 ). What
is important is not whether it is high or low detail, but whether it is the right level of
detail. When making an object for rendering, the goal is to determine the optimal
level of curve detail for the object relative to how it will be used or viewed by the
camera. This varies considerably on the type of project.

7.8 Output Resolution

Output resolution affects modeling and texturing choices because it determines
how many rendered pixels will be used to represent each object in a scene. If an
airplane will be so small in a scene that none of its textures are visible, should it
be textured? If it should be textured because the textures are visible, what is the
optimal resolution for those textures? The number of available pixels in a render
defi nes the maximum output resolution. Table 7.4 provides a list of popular output
resolutions for different formats.
No polygon can be represented on screen or in print with less than one pixel.
Sub-pixel data can infl uence the color of a pixel, but will not change the represen-
tation of polygonal boundaries. This might indicate that a scene shouldn't have
more polygons than there are pixels available to draw them with. Often this is not
true because the scene might require camera movement through a complex model
that contains more polygons than can be drawn to the screen in any given frame.
The additional polygons are revealed by camera movement, so they must be present
at render time even if they will not be rendered in every frame.
Most CG compositions (arrangements of visual objects) do not fi ll the entire
screen with a single object. More often, there is a range of near and far objects.