Graphics Programs Reference
In-Depth Information
whereas changing multiple settings forces you
to guess which one altered your render time. If
you find that something in particular is slowing
down your renders without contributing much
to the final image, get rid of it.
Render Layers
As the first step toward splitting the Bat Creature
into two render layers , I split my scene into four scene
layers . On (scene) layer 1, I placed the body (with
Subdivision Surface and Displace modifiers) and the
teeth and nails. On layer 2, I placed the eye objects,
along with the Hemi light I created to light just
the eyes (using the This Layer Only option for the
lamp). On layer 3, I placed the duplicated body that
I had used to create the hair (with Emitter turned
off in the Render panel of the Particles tab so that
only the hair rendered). Finally, on layer 4, I placed
my lamps, the camera, and my floor plane.
Next, I set up two render layers. On the first, I
disabled Strand under the Include settings of the
Layers panel. For the other, I disabled Solid so that
normal meshes wouldn't be rendered while my
strand hair would. I named the first layer body and
the second strand .
For the body layer, I enabled an ambient occlu-
sion pass under Passes in the Layers panel. The
result when rendered was two separate layers, as
shown in Figure 14-4. When looking at the render
(choose Render Result from the image selector
drop-down menu), you can switch between these lay-
ers using the drop-down menu in the header of the
UV Image editor.
In the Layers panel, the options and settings you
choose apply only to the currently selected render
layer. In other panels of the Render tab, options
apply across all render layers. I set the Alpha option
in the Shading panel to Straight Alpha and turned
off Ray Tracing to speed up renders. (I didn't need
to use ray tracing since I was using buffered shadows
for my spot lamps and approximate ambient occlu-
sion.) I set the render size to 2200×3000 pixels in
the Dimensions panel, and pressed Render (F12) to
start rendering.
Minimize surplus geometry. Once you have the
camera angle that you want, start getting rid
of objects that won't be seen in your render by
deleting them or temporarily shifting them to
other layers. This will reduce the amount of
geometry Blender has to keep track of when
rendering and will speed up your renders!
This trick is often helpful when working with
environments.
Simplify lighting. Try to simplify the settings on
your lamps and see whether you can eliminate
some. In particular, look at the shadow settings:
Will a smaller shadow-buffer resolution really
make much difference, or does a ray-traced
lamp need quite so many samples?
As you become more familiar with Blender,
you'll soon learn which settings impact render time
for different aspects of scenes. In the meantime, the
time you spend experimenting and simplifying your
scene will almost always speed up render times.
The Compositor
You've pressed F12 to render, and your image is fin-
ished, right? Not quite. Now it's time to post-process
the final renders using Blender's compositor and
GIMP. Blender's compositor is node based and uses
the Node editor (which we explored in “Editing
Node Materials” on page 200). In this section, I'll
show you how to use the compositor to apply effects
such as depth of field, bloom, and color grading
and to combine separate render layers into one final
image (see Figure 14-5). I'll also show you how to
use GIMP for painting and touch-up.
Compositing the Passes
After rendering, I used Blender's compositor to com-
bine the layers. I wanted to achieve certain effects
with the compositor, in the following order:
Rendering and Compositing the
Bat Creature
I wanted to show the final Bat Creature on a dark
background with a little color grading. To facilitate
this, I split the rendering into two layers: one for
the fur and one for the rest of the body. I planned
to create a simple, dark-colored background in the
compositor with a slight vignette to darken the cor-
ners and keep the focus on the bat.
1.
Add some extra ambient occlusion to the body
render layer.
2.
Combine the body and fur layers into one image
with a plain background.
3.
Soften the lighting in the image using a bloom
effect.
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