Unity performs shadow mapping to render real-time shadows.
Shadow mapping is the process of creating shadow textures called shadow maps. Unity generates a shadow map from the perspective of a light in a similar way to how a cameraA component which creates an image of a particular viewpoint in your scene. The output is either drawn to the screen or captured as a texture. More info
See in Glossary generates a depth texture. If you consider a camera at the same location as the light, the areas of the sceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary that the camera can’t see are the same areas of the scene that rays from the light cannot reach. Those areas are in shadow.
Unity populates the shadow map with information about how far rays from the light travel before they hit a surface, and then samples the shadow map to calculate real-time shadows for GameObjectsThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary that the light hits.
The larger the shadow map resolution, the better Unity can capture small details in the shadow-casting geometry, and the more precise the shadows can be. Larger shadow map resolution also requires more memory bandwidth.
For information on configuring the shadow map resolution, refer to the following pages:
To create a shadow map for a point light, Unity captures the scene in six directions. The performance impact is similar to rendering shadows from six spot lights, and increases the number of draw calls significantly.
On mobile platforms, this process uses a significant amount of the available resources per frame. Reduce the number of point lights within the camera view as much as possible.
Real-time shadows from spot lights are significantly faster to render than real-time shadows from point lights.