diff --git a/demo2.cpp b/demo2.cpp
index 90ac032..c2c93e7 100644
--- a/demo2.cpp
+++ b/demo2.cpp
@@ -493,6 +493,9 @@ Vector2D shotPosition;
 Vector2D shotDirection;
 bool shotFired = false;
 
+uint8_t previousColumn = 255; ///< Helper for pixelIntensity.
+int8_t pixelIntensity = 0; ///< Precomputed column intensity addition.
+
 /**
   Function for drawing a single pixel (like fragment shader).
 */
@@ -506,7 +509,17 @@ inline void pixelFunc(PixelInfo pixel)
   if (pixel.isWall)
   {
     c = sampleImage(textures[pixel.hit.type],pixel.hit.textureCoord,pixel.textureCoordY);
-    c = addIntensity(c, 1 - pixel.depth / (UNITS_PER_SQUARE * 2) + (pixel.hit.direction % 2 == 0 ? 2 : 0));
+
+    if (previousColumn == pixel.position.x)
+    {
+      c = addIntensity(c,pixelIntensity);
+    }
+    else
+    {
+      // optimization: precompute intensity for the whole column
+      pixelIntensity = 1 - pixel.depth / (UNITS_PER_SQUARE * 2) + (pixel.hit.direction % 2 == 0 ? 2 : 0);
+      previousColumn = pixel.position.x;
+    }
   }
   else
     c = pixel.isFloor ? cFloor: cCeiling;