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130 Chapter 17: Rendering
Top: At m o s p h ere
Second from top: Shadow element
Middle: Diffuse + Specular + ... (other elements)
Bottom: Background
"Screen" Compo siting for Specular and
Reflection Elements
The other exception to additive composition is
when specular or reflection elements have been
generated by certain material shaders. These
shaders generate specula r and reflection elements
you must composite differently:
•Anisotropic
•Multi-Layer
• Oren-Nayar-Blinn
Shaders are assigned on a per-material basis,
in the Material Editor. If you render specular
or reflection elements in a scene that uses these
shaders, then composite them with the diffuse and
other for eground components (aside from colored
shadows, as descr ib ed above), by overlay i ng
them using an operation called "Screen" in some
compositing programs.
Screencompositingusesthisformulatocombine
elements:
Background * (1 - F oreground) + Foreground
The background is multiplied by the inverse of the
foreground color, and then the foreground color is
added to the result.
For more information, see the documentation for
the compositing program you use.
Pr ocedur es
To have the R ender Elements dialog a ssign names to
the rendered element f iles automatically:
1.
In the Render Scene dialog’s Common
Parameters rollout, use the Files button to
assign an output file name and file type for the
(entire) rendered scene.
2. In the Render Elements rollout, use the Add
button to add elements for rendering.
You can render elements to fi les without rendering
theentirescenetoafile,butinthiscase,youhave
to assign the files for the elements individual ly or
"by hand."
To add an element for rendering:
1.
Click Add.
2. In the Render Elements dialog, do one of the
following:
• Click to highlight the name of an element,
and then click OK.
• Double-click the name of an elem ent.
If you have assigned a file name for the entire
rendering, the new element is assigned a file
name automatically. Otherwise, use t he Files
button in the Selected Element Parameters
group to assign an output file name and file
type for the element rendering.
3. Iftheelementisone(suchasBlendorZBuffer)
that has additional parameters, adjust these
parameters in the appropriate rollout.
To render the separate elements:
1.
Add the elements you want to render.
Tip: You can use the Enable button (in the
Selected Element Parameters rollout) to disable
individual elements for a particular rendering
pass.
2. If you haven’t assigned file names automatically,
use the Files button in the S elected E lement
Parameters group to assign an output file name
andfiletypefortheelementrendering.
3. Make sure Elements Act ive (at the top of the
Render Elements rollout) is turned on, a nd
then click Render to render the scene.