Graphics Programs Reference
In-Depth Information
These seings will create a linear gradient, running verically. The high brightness
value causes it to be enirely white but if we set its value down to 0 , the resuling
gradient will look enirely black. Since we need this change to happen automaically
when rendering, let's animate it.
24. Go to frame 190 of the animaion ( Timeline , just below the 3D View ), put the
mouse pointer over the brightness control for the blend_fade texture, right-click,
and select the Insert Keyframe entry from the menu.
25. Now go to frame 200 of the animaion, set the brightness value to 0 and add
a keyframe for it (right-click, Insert Keyframe ). This way, we get a customized
transiion efect when we compose the inal video.
The final part of the task is the one that is needed to actually perform the control of
the alpha channel of the rendered image to get the custom transiion that we just
created with the Blend texture; for that, we need to create two Render Layers and
then use the node compositor.
26. First, go to the Render tab of the Properties Editor , locate the Layers panel, select
the default render layer and rename it as object . In the Scene butons grid, select
layers 1 and 2, and in the Layer butons grid, select only layer 1.
27. Next, create a new Render Layer and name it alpha ; the Layer butons grid must
have selected only layer 2. It's a good idea to check that all the objects of the scene
are associated with layer 1, except for the alpha_control object, which must be
associated only with layer 2.
Before going to the node compositor, let's take a couple of minutes to set up some
useful defaults on this scene.
28. In the Render tab of the Properties Editor , locate the Output panel and set it as
follows:
F Path: /tmp/render/seqs/ (Append C: at the beginning and change the
forward slashes into back slashes if working in the Windows operaing system.)
F File Format: Targa
F Color Mode: RGBA
Seing these opions now will save us some typing later, since this scene will be
duplicated (thus used as a template).
It's now ime to go to the Node Editor and create the necessary node setup. Before
building it, let's look at a screenshot showing it finished:
 
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