Graphics Reference
In-Depth Information
Figure 12.31   Adding  the Earth. Well,  the Earth-monkey.
the Vector pass for each render layer in the Render properties to get Speed to show up as an output in
the compositor. You will also have to re-render to get the Speed data to appear.
One final thing to note about this construction is that the Vector Blur is applied to the image after the
Alpha Over procedure. Applying the blur to the raw render data before it is combined with the background
is extremely difficult, due to the way Vector Blur deals with Alpha. You can try it if you like, but unfor-
tunately it doesn't work like you'd expect. Combine your image with Alpha Over first, then Vector Blur.
If you were going to render out this entire 90-frame animation at this point, it wouldn't work. Everything
would be fine until the Earth passed behind the sun. Figure 12.34 shows a render with our current com-
posite settings on frame 44. The Earth is behind the sun from a 3D perspective, so it shouldn't show up
in the final image. However, there it is.
The problem is that we're performing the Earth's Alpha Over operation after the sun is already composited
into the background. To make it right, we would have to switch the order in which the whole image is
composited: Earth first, followed by the sun. Of course, that setup would then fail when the Earth passed
in front of the sun. As the sun would be composited last, it would still fall in front of the Earth.
The solution is to leave the node tree as it is, but to give it a little more information to work with. Back
in the Render Layers panel of the Render properties, select the “Sun” Render Layer. In the Include section
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