Rendering: Faster, Processor! - Blender Foundations: The Essential Guide to Learning Blender 2.6 - page 330

with Shift-B . A crosshairs appears, just
like with Border Select, and you LMB
drag to define a region. Rendering now
will only render the portion of the image
within that border. To clear the border
and render the entire image, you can
either Shift-B Border Select outside of
the Camera view, or disable the Border
option on the Dimensions panel of the
Render properties.

When it comes to reducing quality, you
have many more options. Once again,
you'll take a different approach depend-
ing on if you're performing overall “look and feel” adjustments or doing detail work.

Figure 12.5 No anti-aliasing; time: 0:09.

For overall work, the most effective thing to do is disable anti-aliasing. This will severely compromise
image quality, but you'll gain a lot of speed. All of the other features still work—shadows, textures, ray
tracing, subsurface scattering (SSS)—so you get a view of what things will actually look like. They'll just
have ragged edges. Figure 12.2 shows a full-resolution render with anti-aliasing disabled. If you really want
a speed boost for doing “overall” work, disable anti-aliasing and reduce the size percentage, as shown in
Figure 12.5 .

To take quality and feature reduction farther you have to consider your scene. Do you use ray tracing
(refraction, reflection, shadows)? If so, how integral is it to the aspects of the scene you are working on?
In the example scene, the shadows from the main window and wall bounce are provided by ray tracing
on area lamps. Disabling ray tracing kills that and the wood reflections. Figure 12.6 shows the result.
Consider what you're working on, and if you can get along without ray tracing, disable it in the Shading
panel. Likewise with shadows and subsurface scattering.

In fact, unless you're actively tweaking a
material that uses SSS like skin, it's a
good idea to disable it for speed. SSS
adds a whole separate rendering pass to
the process, and can take up a significant
amount of time under certain conditions.
Get your skin and other SSS-based mate-
rials as you like them, then disable SSS
until final rendering.

Disabling shadows is a little harder to
justify for stills. However, when working
with animation and correct motion under Figure 12.6 No ray tracing or subsurface scattering; time: 2:03.