Unbiased Truck Soccer: Sunny sky with only a few traces of rayn!

Another test in the quest for faster convergence speed, this time using a skydome and sun.

One of the advantages of using a skydome to light the scene is that the difference between 2 and 3 bounces of indirect light is not as large as when using an area light:

max path length 1 (zero bounces)

max path length 2 (1 bounce)


2 bounces


3 bounces

Another advantage is the very fast convergence speed compared to using area lights due to the fact that almost every pixel can 'see' the skydome. Only the pixels that are occluded from the skydome (e.g. the ground patch under the car) clean up slower because they are indirectly lit. Using bidirectional path tracing would greatly increase the convergence speed of these pixels (edit: as pointed out by Iliyan in the comments, bidir path tracing would actually perform worse in this outdoor scene where standard path tracing shines).

An overcast sky can be simulated by using only the skydome for lighting (without an emitting sun sphere):

In this case, the noise clears up very fast with just a few samples. This lighting setup will be used for the Unbiased Truck Soccer game.

Download the executable for this sky test at http://code.google.com/p/tokap-the-once-known-as-pong/downloads/list (package updated with glass sphere for some nice caustics)

To brighten/darken the sun, select the sun sphere by right-clicking it, click the 'emi' button on the top right of the screen and change the values at the bottom of the screen to e.g. 10, 10, 5. Overbrightening the sun will cause the shadows to look sharper and more pronounced, but will also increase the noise to unacceptable levels: