My vote for the most useful Cinema4D plug-in. I have just purchased a plug-in that will save tons of time and allow me to really advance my craft of rendering a building in C4D.
I am talking about SNIPER PRO.
This plug-in allows Cinema to act like Artlantis. Real time updates to a rendered image while you adjust lights, reflections, textures and objects. You can toggle it on or off at will resulting in a small preview window that shows a simplified view of your finished rendering. This feature is great for getting those shadows placed just right, or the overall light levels adjusted. The remarkable thing about this simple and inexpensive plug in is that you can freely experiment with any rendering variable and within seconds see the effect. Cinema has so many items which can be adjusted up and down, with this plug in you will see the visual and know what effect it will have on the render time. If the SNIPER PRO render time changes from 15 sec to 20, you can be assured the final render time will increase a similar amount.
For example, the Galaxy Office Building File built by Michael Rensing was used as a test. This 162 MB file renders in 7 minutes with a dual processing G5 - 2 GHz machine. With SNIPER PRO that same file previews inbetween 7 sec and 15 sec (Depending on the preview quality).
Look at the sample image suppled with this post. The upper right shows the first view, you can easily notice the washed out building and the dreaded shadows of death, (yes, thank you Dwight).
Without wasting any time you can jump into the setting and adjust the black shadows to a dark blue or magenta. Within 7 seconds you can see the overall effect. See the preview image to the upper right. Then all you need to do is final render and you are done.
The cycle of RENDER - RENDER - RENDER - AREA RENDER - AREA RENDER - is completely out the door. If you were to do this loop the time you would spend could total over 30 minutes ((with SNIPER PRO it is reduced to less that two minutes.)) Giving you plenty of time for asking the boss for a raise.
Oh, and YES! it does the same trick with radiosity - it is simply amazing to see a radiosity solution within 30 seconds
Try this out yourself if you don't believe this post, there is a fully operational DEMO available at :
http://www.tools4d.com
While you are there check out STORM TRACER, a plug in that can simulate 3D grass. There are plenty of other great plug-ins too. Enjoy!