by Julieanne Kost
Style (or Layer Style) is one of the many attributes that can be changed over time using keyframes in the Timeline panel in Photoshop CS6. Most of the Layer Style options use directional lighting to create the desired effect (such as drop shadows, bevel and emboss, inner shadows etc.).
Depending on your image, you may have a number of individual objects (type layers, video clips, shape layers etc.) which you want to cast shadows at different angles. This can be accomplished by turning off the Global Lighting check box in the Layer Styles dialog for each layer. If, however, you want all of the objects to cast the same shadow at the same angle, then either turn on the Global Lighting check box in the Layer Styles dialog for each layer or, use the Global Light Track on the Timeline panel to change all layers lighting (and therefore the direction of the shadows) at once. And of course the Global lighting direction can be changed, over time, using keyframes!