Archive notice: This article was originally published on February 1, 2017. Links and embedded videos are preserved as part of the historical record.
UV Paint is a plug-in for Cinema 4D that builds on the sculpting tools and enables you to paint directly in the viewport. Its current main functions include paint brushes, a material manager, and a content viewer. Here you can see a preview from GameLogicDesign of the upcoming 1.5 release. It includes, among other things, integrated functions for vector graphics with corresponding SVG support.
Textures and HDR Browser
Projection Painting with UV Paint
You can find more information about it on the blog and the official site. Pricing for the plug-in starts at €91 and it offers either a single or floating license. You can find the link here.