On the PrmanRender tab, you can select if you want to render shadows, reflections, refractions and depth of field, or all of them into your result. All these effects are calculated using a retracing method that is based on drawing rays from the camera to the object. Check the box for:
• shadows - to add shadows to your render. You can adjust the parameters for your shadows on your Light node’s Shadows tab. For example, if you adjust the sample width, the shadows are softer. For more information, see Casting Shadows.
• reflections - to add reflections to your render. You can adjust the parameters for your reflections on your Reflection node’s properties panel. See Using the Reflection Node.
• refractions - to add refractions to your render. You can adjust the parameters for your refractions on your Refraction node’s properties panel. See Using the Refraction Node.
• dof - to add depth of field to your render.