SHEnvironmentMap

Using Nuaj and Cirrus to create test projects is alright, but came a time where I needed to start what I was put on this Earth to do : deferred HDR rendering. So naturally I started writing a deferred rendering pipeline which is quite advanced already. At some point, I needed a sky model so, naturally again, I turned to HDR rendering to visualize the result.

When you start talking HDR, you immediately imply tone mapping. I implemented a version of the "filmic curve" tone mapping discussed by John Hable from Naughty Dog (a more extensive and really interesting talk can be found here [1]) (warning, it's about 50Mb !).

Your typical ugly scene with no ambient

But to properly test your tone mapping, you need a well balanced lighting for your test scene, that means no hyper dark patches in the middle of a hyper bright scene, as is usually the case when you implement directional lighting by the Sun and... no ambient !

That's when I decided to re-use my old "ambient SH" trick I wrote a few years ago. The idea was to pre-compute some SH for the environment at different places in the game map, and to evaluate the irradiance for each object depending on its position in the network, as shown in the figure below.

The algorithm was something like :

For each object
{
 Find the 3 SH nodes the object stands in
 ObjectSH = Interpolate SH at object's position
 Render( Object, ObjectSH );
}