Do some more refactoring

frontend/src/scripts/drawing/shaders/cave-distance-fs.glsl

@@ -6,7 +6,7 @@ precision mediump float;
 #define CAVE_COLOR vec3(0.36, 0.38, 0.76)
 #define AIR_COLOR vec3(0.7)
 #define DISTANCE_SCALE {distanceScale}
-#define EDGE_SMOOTHING {edgeSmoothing}
+#define DISTANCE_OFFSET {distanceOffset}
  
 uniform float maxMinDistance; 
 
@@ -23,28 +23,25 @@ in vec2 worldCoordinates;
 out vec4 fragmentColor;
 
 void main() {
+    float realDistance = 0.0;
+
     #if LINE_COUNT > 0
         float minDistance = maxMinDistance;
 
         for (int i = 0; i < LINE_COUNT; i++) {
-            Line line = lines[i];
-            vec2 pa = worldCoordinates - line.from;
-            vec2 ba = line.toFromDelta;
-            float baLength = length(ba);
-            // todo: do we really want this dot(pa / baLength, ba / baLength)
-            float h = clamp(dot(pa / baLength, ba / baLength), 0.0, 1.0);
-            float lineDistance = distance(pa, ba * h) - mix(line.fromRadius, line.toRadius, h);
+            vec2 pa = worldCoordinates - lines[i].from;
+            vec2 ba = lines[i].toFromDelta;
+            float h = clamp(dot(pa, ba) / dot(ba, ba), 0.0, 1.0);
+            float lineDistance = distance(pa, ba * h) - mix(lines[i].fromRadius, lines[i].toRadius, h);
 
             minDistance = min(minDistance, lineDistance);
         }
 
-        float distance = -minDistance;
-        fragmentColor = vec4(
-            mix(CAVE_COLOR, AIR_COLOR, clamp(distance, -EDGE_SMOOTHING, 0.0) / EDGE_SMOOTHING + 1.0),
-            distance / DISTANCE_SCALE
-        );
-    #else
-
-        fragmentColor = vec4(AIR_COLOR, maxMinDistance / DISTANCE_SCALE);
+        realDistance = -minDistance;
     #endif
+
+    fragmentColor = vec4(
+        mix(CAVE_COLOR, AIR_COLOR, clamp(realDistance, 0.0, 1.0)),
+        (realDistance + DISTANCE_OFFSET) / DISTANCE_SCALE - 1.0/255.0
+    );
 }