When working with complex scenes interactive performance can slow down. There are a number of ways to remedy this problem.
Default Material – Shades your entire scene with a default shader regardless of what materials and textures are applied to each object. This reduces the complexity of the scene view display without actually affecting the render.
You can turn on the Default Material by selecting Shading > Use default material.
Interactive Shading – Lets you display the scene with less complexity when performing a variety of interactive operations such as camera tumbles and dollies. This is useful for increasing performance in scenes that slow down when modified.
You can turn on Interactive Shading by selecting Shading > Interactive Shading.