Improve color accuracy

Author: vanruesc

src/materials/shaders/convolution.downsampling.frag

@@ -3,8 +3,8 @@
 
 // (1 / 4) * 0.5 = 0.125
 #define WEIGHT_INNER 0.125
-// (1 / 9) * 0.5 = 0.0555555
-#define WEIGHT_OUTER 0.0555555
+// (1 / 9) * 0.5 ≈ 0.05556
+#define WEIGHT_OUTER 0.05556
 
 in vec2 vUv;
 in vec2 vUv00, vUv01, vUv02, vUv03;