room changes

shaders.lua

@@ -128,6 +128,44 @@ wireNeonShader = love.graphics.newShader[[
   }
 ]]
 
+-- World renders a neighbouring room twice for the porous seam: once through
+-- its own active channels and once through the current room's channels. This
+-- shader only controls the alpha of that second, already-authored render, so
+-- it never approximates the game's literal RGB colour treatment.
+porousRoomBoundaryShader = love.graphics.newShader[[
+  extern number porousTime;
+  extern vec4 porousRoomRect;
+  extern vec2 porousDirection;
+  extern number porousDepth;
+
+  float porousWave(vec2 point) {
+    float broad = sin(point.x * 0.095 + point.y * 0.071 + porousTime * 1.45);
+    float fine = sin(point.x * 0.231 - point.y * 0.187 - porousTime * 2.20);
+    return broad * 0.105 + fine * 0.050;
+  }
+
+  vec4 effect(vec4 color, Image texture, vec2 textureCoords, vec2 screenCoords) {
+    vec4 alternateView = Texel(texture, textureCoords) * color;
+    vec2 local = screenCoords - porousRoomRect.xy;
+    vec2 size = porousRoomRect.zw;
+    if (local.x < 0.0 || local.y < 0.0 || local.x > size.x || local.y > size.y)
+      return vec4(0.0);
+
+    float depth;
+    if (porousDirection.x > 0.5) depth = local.x;
+    else if (porousDirection.x < -0.5) depth = size.x - local.x;
+    else if (porousDirection.y > 0.5) depth = local.y;
+    else depth = size.y - local.y;
+
+    float towardSeam = 1.0 - smoothstep(0.0, porousDepth, depth);
+    // Animated fingers soften the fifty-fifty transition across the visible
+    // overlap while preserving the pixels of the real alternate room render.
+    float mask = smoothstep(0.18, 0.82, towardSeam + porousWave(screenCoords));
+    alternateView.a *= mask;
+    return alternateView;
+  }
+]]
+
 function drawGoopySprite(sprite, x, y, scale)
 	local w, h = sprite:getWidth(), sprite:getHeight()
 	local time = love.timer.getTime()