Graphics Programs Reference
In-Depth Information
the samples are blended together. (Essentially, the
image is rendered multiple times, and the results
are blended.) The number of samples is determined
by the Motion Samples setting, and the amount of
time in frames over which the samples are taken is
determined by the Shutter setting.
meaning that if you have eight threads, you will be
able to render eight tiles simultaneously.
Tweaking the Tiles settings can make a big dif-
ference in your render times. Using too few tiles can
mean that processor threads are left idle once all
available tiles are being rendered, even if there is
plenty of your image left to be rendered. Using too
many tiles uses more memory without speeding up
the render. The optimum number of tiles is gener-
ally between 16 (4×4) and 64 (8×8), with more com-
plex scenes benefiting from more tiles.
The other settings in this panel are even more
technical and can usually be left at their defaults.
For more on these settings, try
http://wiki.blender.org/
.
Shading
The Shading panel lets you turn on and off differ-
ent rendering options, including Textures, Shadows,
Subsurface Scattering, Environment Mapping, and
Ray-Tracing options. To speed up renders, turn off
unneeded shading options.
The Alpha drop-down menu lets you choose
how to render the background of your image. Sky
renders the sky colors and textures set in your global
settings. The Straight Alpha and Premultiplied
options render the background of your image as
transparent. In the case of Premultiplied, the RGB
values of transparent or partially transparent pixels
are multiplied by the alpha value on output. This
method of encoding alpha values is also referred to
as
associated alpha
and is required for some image
formats, like TIFF and PNG. It's also useful for com-
positing because combining images this way gives
better results, though Blender's compositor has tools
for working with both premultiplied and unpremul-
tiplied alpha. Straight Alpha skips this step and ren-
ders unassociated alpha images instead.
Post-Processing
The Post-Processing settings determine the post-
processing effects applied to your image. The
relevant ones are the checkboxes that turn on
Compositing and the Sequencer (Compositing
should be turned on). Dither adds subtle variation
to the colors of pixels, preventing color banding in
images with smooth gradients. The Edge setting
draws cartoon lines around an image's geometry,
with the strength of the line effect determined by
the Threshold setting and the color of the lines
determined by the color selector directly below the
Threshold setting.
Stamp
The Stamp settings let you stamp your image with
data about the render, such as the time it was ren-
dered, the filename, the frame number, and so on.
Stamp is often useful when rendering animations,
but it's not of much use to us for our projects.
*
If the above discussion on different methods of encod-
ing alpha values seems complex, it's because it is. I've
covered it only very briefly here, but it's actually a
pretty deep topic. For more information, try searching
http://w w w.blender.org/
and the Blender wiki for
Color Management.
Output
The Output settings determine where the output of
your renders is saved and in what format. Animation
frames are saved automatically, but single-frame
images must be saved manually. The default output
directory (
/tmp/
on Mac and Linux systems or the
Temp folder on Windows) determines where anima-
tion frames are saved, but you can change this to
a directory of your choosing. The output format is
determined by the drop-down menu, which includes
options for what color information to save (black
and white, RGB, or RGB and alpha).
Performance
The Performance panel contains a number of options
that can affect how fast Blender will render and how
much impact rendering will have on your com-
puter's resources. Blender splits up images to be
rendered into multiple tiles, which are then ren-
dered individually. The most important settings
are Threads and Tiles. When set to Fixed, these
settings let you specify how many tiles will be ren-
dered at once (up to twice the number of processor
cores you have).
The Tiles settings determine how the image to
be rendered is broken up into tiles along the
x
- and
y
-axes. Tiles are rendered one at a time per thread,
Bake
These settings are discussed in detail in Chapter 11.
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