In this example the closest object are white while the furthest are black and a nice smooth gradient (32bit float is a must for this pass) indicates how relatively each things are in the Z axes compared to the camera, that re-creating a sense of depth that could be use. That way you would render a separate ZDepth pass that could be use to control precisely the dofBlur. What you could do is generate a ramp to which intensity would vary depending on the distance from the camera the object is. It sometime help to smooth shadows accurately to the original lightning system by blending it with the rendered frame using a fusion mod such as screen/plus/add/overlay. 3D rendering is mostly re-use in compositing to 're-light' a scene rather than lightning from scratch. To be honest, I've rarely heard people use Fusion/Nuke to do internal 3d Render beside doing matte painting. Fusion has been used on feature films like Thor, The Amazing Spiderman 2, and The Hunger Games, as well as hit television shows like Orphan Black, Breaking Bad, Grimm, Adventure Time, Downton Abbey and the Emmy award winning Battlestar Galactica Thousands of Hollywood’s biggest blockbusters and hit television shows use Fusion to create their groundbreaking visual effects. That’s super easy and extremely fast! You get a massive range of features and effects included, so you can create exciting broadcast graphics, television commercials, dramatic title sequences and even major feature film visual effects! With over 25 years of development, Fusion has been used on over 1000 major Hollywood blockbuster feature films! Fusion features an easy and powerful node based interface so you can construct complex effects simply by connecting various types of processing together.

Fusion is the world’s most advanced compositing software for visual effects artists, broadcast and motion graphic designers and 3D animators.

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