The process of learning if something is in shadow or not is not as easy as one would think.
Use a texture to store the light levels of a surface.
Shadow Map - 1978
Render a depth buffer from the light source viewpoint and use it to detect what the light can shine on.
Shadow Volume - 1977
Create volumes from the occluders silhouette edges and render them using the stencil buffers.
- Advanced Geometrically Correct Shadows for Modern Game Engines - 2016
- Shadow Map Silhouette Revectorization (SMSR) - 2016
- Efficient Real - Time Shadows - 2012
- Dynamic 2D Soft Shadows - 2013
- Walls and Shadows in 2D - 2009
- Shadows and light on Kepler 22
- View-warped Multi-view Soft Shadowing for Local Area Lights
- Contact-hardening Soft Shadows Made Fast
- View-Warped Multi-View Soft Shadows for Local Area Lights
Real-time Shadows - 2020
Point and Spot Shadows Perspective Shadows
Sparse Shadow Trees - 2016
Raytraced Shadows in Call of Duty: Modern Warfare - 2020
Cascaded Shadow Maps with Soft Shadows
Sample Distribution Shadow Maps