Continue work on shadow rendering

shader/shadow/wallShadow.geom

@@ -13,6 +13,19 @@ vec4 shift(vec4 p) { return vec4(p.xy + (200 * (p.xy - lightPos.xy)), 0, 1); }
 float isLHS(vec2 startV, vec2 testV) {
   return sign(-startV.x * testV.y + startV.y * testV.x);
 }
+// Preprocessed to include ../functions.glsl
+float closestPointOnLineParam (vec2 a, vec2 b, vec2 p) {
+  return dot(p - a,b-a) / dot(b-a,b-a);
+}
+vec2 closestPointOnSeg (vec2 a,vec2 b, vec2 p) {
+  float x = closestPointOnLineParam(a,b,p);
+  if (x < 0) {
+      return a;
+  } else{ if (x > 1) { return b; }
+      { return a + (x * (b- a));}
+  }
+}
+// End include 2023-03-13 15:33:44.454374887 UTC
 // construct a box with openings on bottom face and face away from wall
 void main() {
   vec4 p1 = vec4(gl_in[0].gl_Position.xy, 0, 1);