Graphics Programs Reference
In-Depth Information
bounce on the floor, the ceiling, and the walls a good many times before reaching
one or more light sources.
In short, the main difference between the two rendering engines is due to the fact
that, while in Blender Internal the materials use all the traditional shader tricks of a
scan-line rendering engine such as, for example, the simulated specular component,
the Cycles rendering engine is a path tracer trying to mimic the real behavior of a
surface as closely as possible as in real life. This is the reason why in Cycles we
don't have, for example, the arbitrary
Spec
factor simulating the reflection point of
the light on the surface, but a glossy shader actually mirroring the light source and
the surrounding, to be mixed to the other components in different ratios and so be-
having, in this respect, in a more correct way.
In any case, just for explanatory purposes, in this topic I will still refer to the more or
less blurred point of light created by the reflection of the light source on a mirroring
glossy surface as
Specularity
.
Be aware that the rendering speed in Cycles depends on the device—CPU or
GPU—you use to render your scenes. That is, basically you can decide to use the
power of the CPU (default option) or the power of the graphic card processor, the
GPU.
To set this:
1. Call the
User Preferences
panel (
Crtl
+
Alt
+
U
) and go to the
System
tab, the last one to the right of the panel.
2. Under the
Compute Device
tab to the bottom-left of the panel, select the
one to be used for the computation; to make this permanent, click on the
Save User Settings
button or press
Crtl
+
U
. Now close the
User Prefer-
ences
panel.
3. In the
Properties
panel to the right of the interface, go to the
Render
win-
dow and, under the
Render
tab, it's now possible to configure the GPU
of the graphic card instead of the default CPU (the option is present only
if your graphic card supports CUDA, that is, for NVIDIA graphic cards;
OpenCL, which is intended to support rendering on AMD/ATI graphics
cards, is still in a very incomplete and experimental stage and therefore
not of much use yet).
