Good day. I am Xor and I write shaders for a living.
I recently heard that Construct users were using an old blur shader I wrote in 2015, which is clunky and slow.
So I wanted to offer a better solution. Here's my fast "disk blur".
Preview Image
This method produces the best results when applied directly to an object with no effects or color adjustments before it. This way it can utilize mipmapping (downsampling) for high-radius blurring.
Alternatively, if you need to apply this to a lot of objects you should apply the effect to the layer instead. You won't be able to use mipmapping, so to make it smooth at a high-radius, you'll want to apply the disk blur multiple times at increasing radii:
Layer Blur Example
So to recap, for the best results either apply it as the first effect directly to the object you want to blur or apply it to a layer as many times as need (starting small like 10 and double or triple with each extra pass)
This should produce similar results to mipmapping on the entire layer.
Hope this helps. Thanks