To visualize your scene interactively in the scene view, there are three modes available. Select the renderer you want from the Renderer panel menu. See Panel Menu: Renderer :
Select this option to draw scene views at a high performance and to visualize viewport effects such as ambient occlusion and anti-aliasing. Fidelity of lighting and materials is of a much higher quality in Viewport 2.0 than in the legacy viewports.
See About Viewport 2.0, Viewport 2.0 features and limitations, and Working in Viewport 2.0.
Select this option to draw scene views with low quality settings but reduce draw time.
Select this option to draw scene views with high quality settings.