Maybe you are thinking that we already have shadows in the scene, but actually, we don't. The darker areas of the object, the ones that are not facing the lights, don't have shadows – they are not being lit, and that's quite different from a shadow. In this case, we are referring to the shadows that are projected from one object to another; for example, the shadow of the player being projected on the floor, or from the mountains to other objects. Shadows can increase the quality of our scene, but they also cost a lot to calculate, so we have two options: not using shadows (recommended for low-end devices such as mobiles) or finding a balance between performance and quality according to our game and the target device. In the first case, you can skip this whole section, but if you want to achieve performant shadows (as much as possible), keep reading.
In this section, we are going to discuss the following topics about shadows: