Easier control over World/Environment outputs

Currently the world output is just one slot. It's there and lights, reflects, refracts and shows in anything or not. The only way to counter this is to render with transparent background and set up the different passes in different places in Blender.

Here's how Modo sets up environments as a comparison:

The influence of the environment is split up into the four major parts:

• visible to camera
• visible to indirect rays (lighting)
• reflections in the objects
• refractions

On one hand that's nice because you have more control over what is being rendered in the final image. On the other hand you still havew to set up different environments if you want to split the influences or HDRIs.

Blender could do this much better (and easier) in a node setup, IMO:

This would also counter the problem in the rendred viewport. By default you you have to work either with the full blown HDRI background visible or have 'film' settings set to transparent. and still have no quick and easy control over the background color in the rendered viewport.

Splitting the main inputs of the world into different categories could easily set up the HDRI for reflection and lighting while keeping the background set to a crisper image, simply a dark grey color, or something entirely different.