2 - Final gathering method : a powerful rendering strategy.

 

After receiving and understanding the clever analysis of Luc-Eric, I decided to make some tests. I wasn't the only one, and in one hour, all of us achieved nice looking "Arnold touch" images : a nice and rich object with no particular material effects, a constant sphere above, only Final gathering on, one black light to trigger the process and there we are!

Quickly, I also understood that this technique could easily lead to very interesting and useful rendering strategies. There was no limitation to use a constant diffuse lighting in combination with a regular light that cast shadows to bring more contrasted images. It's only a question of tuning the constant colour of your "sky" to get less overall diffuse lighting, so that you can add a "real" sunlight.

 

 

Above, the same Bugatti. Here, the diffuse lighting is very low and blue, while a warm Area light simulates a sunset effect.
Original rendering : 147,000 polygones ; 947 x 691 ; 2h50' (dual-PIII 733) ; FG Accuracy = 300 / Max rad = 0.01 Min rad = 0.01 ; Area light 4 4

 

The possibilities of this technique are quite numerous : in the Architectural scope, it will help simulating a bad weather like ambiance or a northern light expression for exterior situation of course. See the example below, a "with and without" Final gathering comparison ! (This is not really the best example I can show to illustrate this, but that's a recent project we rendered in XSI and for which Final gathering could have helped a lot).

 

Below, exterior architectural rendering : ray-tracing + Final Gathering. The northern parts of the building are also "lit and shadowed".

 

Note : in this rendering, apart from Final gathering, almost all the metallic parts have glossy reflections, which slows a lot the rendering speed as well !

Original rendering : 86,000 polygons ; 2000 x 1000 ; 4h20' (dual-PIII 733 + dual PII xeon 450) ; FG Accuracy = 100 / Max rad = 0.1 Min rad = 0.1
Note : there are lots of glossy reflections !

 

Below, exterior architectural rendering : standard ray-tracing only. No comment!