From efca7f77025493bcf43865b64141cf0d8ae15537 Mon Sep 17 00:00:00 2001
From: marmottchen <71234931+marmottchen@users.noreply.github.com>
Date: Tue, 15 Oct 2024 21:45:55 +0200
Subject: [PATCH] Optimised line intersection by adding two simple prechecks.

---
 src/pygame_light2d/fragment_light.glsl | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/pygame_light2d/fragment_light.glsl b/src/pygame_light2d/fragment_light.glsl
index 7ed1aa5..fdc125f 100644
--- a/src/pygame_light2d/fragment_light.glsl
+++ b/src/pygame_light2d/fragment_light.glsl
@@ -29,6 +29,24 @@ vec2 uv_to_world(vec2 v){
 }
 
 bool isOcluded(vec2 p,vec2 q){
+    float x1 = min(p.x, q.x);
+    float w1 = abs(p.x - q.x);
+    float x2 = min(fragmentTexCoord.x, lightPos.x);
+    float w2 = abs(fragmentTexCoord.x - lightPos.x);
+
+    if(x1+w1<x2 || x2+w2<x1){
+        return false; //The lines cant intersect because their images on the x-axis dont intersect
+    }
+
+    float y1 = min(p.y, q.y);
+    float h1 = abs(p.y - q.y);
+    float y2 = min(fragmentTexCoord.y, lightPos.y);
+    float h2 = abs(fragmentTexCoord.y - lightPos.y);
+
+    if(y1+h1<y2 || y2+h2<y1){
+        return false; //The lines cant intersect because their images on the y-axis dont intersect
+    }
+
     vec2 v1=q-p;
     vec2 v2=lightPos-fragmentTexCoord;