Line-of-Sight Archive
2D shadow casting in pygame: the block grid becomes a few long edges, rays go to every corner and just past it, and the lit area is drawn from where they hit.
- Role
- Author
- Period
- Oct–Dec 2020
- Team
- Solo
- Stack
- Python · pygame
What I did
A small weekday project: a pygame scene where you place blocks with the mouse (left click adds, right click removes) and press space to switch on a light that follows the cursor.
How it works
- The grid is turned into edges: every block side that faces empty space, with neighbouring sides on the same line merged into one edge. A row of ten blocks becomes four edges.
- From the light, three rays go to every edge corner: one straight at it and two that pass it by 0.0001 rad on either side, so the light can slip past the corner.
- Each ray stops at the nearest edge it crosses (line–line intersection). Sorted by angle, the hit points draw the lit area as a fan of triangles.
- Based on The Coding Train's ray casting video and One Lone Coder's shadow casting video.
Gallery
