eMirage - quick tip : Volumetric light rays with Blender Cycles. 1-create a box adjust its shape and assign to it a new material 2-create a sun lamp, change the sun's color
volumetrics - Volume Scatter in World makes the sky turn black - Blender Stack Exchange
Volume Scatter — Blender Manual
Using volume materials | Blender Cycles: Materials and Textures Cookbook - Third Edition
Volumetric lighting issues - Lighting and Rendering - Blender Artists Community