normal_transform can be non-orthogonal, so after transforming with it
direction vectors must be normalized.
This fixes a bug where President Garter is rendered too specular.
There are two types of fog, linear fog and atmospheric scattering. The
formula for light scattering is incorrect (see the comment in
reign.v.glsl) and therefore not physically correct.
This implements a Phong shading with ambient, diffuse and specular
components, using up to three directional lights and one specular light.
The light calculation is made to match the "high quality" 3D mode of
Toushin Toshi 3.
ReignEngine is the 3D rendering engine used in Toushin Toshi III, and is
the predecessor of the 3D engines for Rance Quest, Rance 9, Evenicle,
etc.
This implements minimal functionality to be able to draw the first 3D
dungeon scene. Many important parts such as motion and lighting are not
implemented yet.
kichikuou