The Indigo 3 series introduced many important features such as realtime editing capabilities, while version 4 of the software adds pure GPU rendering through a vendor neutral OpenCL path tracing engine. Indigo was originally released as freeware until the 2.0 release, when it became a commercial product.
Indigo also supports subsurface scattering and has its own image format (.igi). Indigo features Monte-Carlo path tracing, bidirectional path tracing and MLT on top of bidirectional path tracing, distributed render capabilities, and progressive rendering (image gradually becomes less noisy as rendering progresses). Indigo Renderer is one of the toughest competitions that the finest rendering services have to come across. The plugin can be integrated easily with SketchUp.
Scene data is stored in XML or IGS format. Caravaggio 3D offers a 20-day free trial version for you to analyze how Caravaggio can be a valuable addition to your work. Indigo uses methods such as Metropolis light transport (MLT), spectral light calculus, and virtual camera model. Caustics, as in light that has been focused through a magnifying glass and has made a pattern of brightness on a surface.
It takes far less time to setup than traditional biased or ‘global illumination’ renderers and their interactive, photographic approach lets you concentrate on lighting and composing your imagery. This tutorial was NOT done by me, it was done by Whaat, I just introduce it to the 3D warehouse(DO NOT DOWNLOAD DIRECTLY).