The viewport renderer supports several global lighting modes, from no lighting whatsoever to full lighting with shadows.
Values ¶
            hou.viewportLighting.Off
        
No lighting, constant shaded.
            hou.viewportLighting.Headlight
        
Basic lighting from a single directional light defined in the display options.
            hou.viewportLighting.Normal
        
Good quality lighting from up to 10 basic lights (area lights modeled as point lights, limited environment lights).
            hou.viewportLighting.HighQuality
        
High quality lighting from an unlimited number of lights including area, geometry, environment and ambient occlusion.
            hou.viewportLighting.HighQualityWithShadows
        
High quality lighting with shadows.