wip readme presentation

README.md

@@ -60,6 +60,20 @@ This technic has the hability to not show hidden area by design, which is a grea
 
 How it works :
 
+1. first you determine the position and orientation of the viewer in the map, and the distance and width of the screen
+	-> png map with eye and screen
+2. then you will scan this fictif screen with rays, each ray will correspond to a column in the 3D view
+	-> gif rays scanning, then columns simutanously appear on both side
+3. when a ray reaches a wall, it draw it in the 3D view
+	-> png one ray on close box
+4. the height of the wall is inversely proportional to the length of the ray : the shorter the ray, the higher the wall
+	-> png two rays, one for each box
+5. so a full scan gives the illusion of perspective
+	-> gif scan of the rays with fish eye
+6. but this gives rounded walls, like a fish eye effect, because rays change length while scanning the wall, so we must apply a correction according to the angle
+	-> gif scan with strait walls
+
+---
 1. first you determine the position and orientation of the viewer in a plan,
 
 ![](assets/raycast_step1.png)