implement realtime sun light on tiled renderer

[illwieckz]

May be cool to have the sun from ioquake3 opengl2 renderer, or another implementation that does the job.

Note: “opengl2 renderer” means “second renderer”, not “renderer using OpenGL 2”.

[illwieckz]

We have that:

    // directional sun lighting ( Doom3 style )
    gl_shaderManager.load( gl_forwardLightingShader_directionalSun );

But it relies on the forward renderer, something we want to drop (#236)

@cmf028 do you think such sunlight would require the same design required by realtime shadows (#242) and would be able to leverage it? Or does it require something else?

[illwieckz]

from https://github.com/DaemonEngine/Daemon/issues/662#issuecomment-1199857651 :

Here is an example of how looks ATCS (not HD) map on Q3 tremulous mod on ioquake3 with classic lighting:

Here is an example of how looks ATCS (not HD) map on Q3 tremulous mod on ioquake3 with r_forceSun 1:

Also not that it does not benefit from specular/normal/relief mapping here as none of this is implemented.