08 Jan Custom Blur Shader for Unity3D
During the development of the HOTAH game under the DADIU initiative, I found myself flirting with Unity shader programming. More specifically, the art direction suggested we should have some nifty looking water which reminds of the milky water in Limbo. Limbo being a pure 2D game and us working in 2.5D, I got away with developing a custom blur shader.
While Unity 3D offers a lot of professional shaders out of the box, it only offers a blur shader as a post-processing effect, meaning that the blur is only applied to the whole scene rendered by the camera. As we needed selective blur, I developed a shader that renders what is behind the object it is applied to and then applies a Gaussian blur to the grabbed texture.
Some Theory
Of course, you can read all the math behind it on Wikipedia (don’t forget to check notes and references as well), especially if you need to calculate the weights for the filter. Just to get you in the mood, you can visualize how the blurring happens using the image below.
Visualizing the Blur Shader
While the blurring could be done in only one pass, it is computationally safer to do it in two passes: one for the vertical blurring and one for the horizontal one. For example, since I am using a mask size of 5 , the cost for two passes is only 11+11 = 22 texture samples, while it would take 11*11=121 texture samples for a single pass.
Demonstration
You can see a demonstration of the shader below. It works best with values between 0 and 2. It starts showing huge offset for higher values and I’m still trying to find a suitable solution for that (suggestions are welcome) .
Where to get the blur shader
As of yesterday, I have made the shader available on the Unity store for free, and you can access it through this link. I am also open to suggestions in making my shader better, as there’s always room for improvement.
References:
Lukas
Posted at 19:40h, 12 JanuaryHello, it doesn’t work in unity 4.0 ?
Ana Todor
Posted at 17:49h, 26 JanuaryHi, what error do you get?
Rog
Posted at 15:15h, 06 MarchThanks very much for this, the usage via a plane works brilliantly for layered render textures.
Horizontal-only, or vertical-only versions could be interesting, especially animated (via iTween or otherwise). I may play around with that. =)
And yes it’s working well for me (Unity 4 Pro).
Ana Todor
Posted at 16:41h, 07 MarchHey Rog, feel free to go wild. That’s why I put it out for the masses ;).
And thanks or testing it out in Unity 4.
Ana Todor
Posted at 16:42h, 07 MarchAlso yay, my free blur shader has been rated with 4 stars on the Unity Asset store! Good enough for my first submission :P.
Hriday
Posted at 11:11h, 30 JulyWhich one is that? I didn’t see it there.
Philippe Blanchard
Posted at 22:52h, 15 MarchHi, this is super useful and interesting but for some reason when I use it the blurred image is flipped in y, I must be doing something wrong.
Ana Todor
Posted at 00:10h, 18 MarchHi Phillipe, you’re not doing anything wrong. I think that relates to the rendering path configured with Unity. Try going to Player Settings > Other Settings>Rendering Path and play with that around. If that doesn’t work, I think you can modify the code to do an image flip. If I remember well, I might have done that myself and you simply need to remove the code where I invert the image.
David
Posted at 16:40h, 10 MayHi Ana,
the shader has an error “Program ‘vert’, incorrect number of arguments to numeric-type constructor (compiling for d3d11) at line 25. Same for d3d11_9x.
The sample scene shows the pink default shader. Using Unity 4.1.1f4
Ana Todor
Posted at 20:40h, 15 MayHi David,
Sorry for the late answer, I maintain this blog and shader in my free time and I haven’t had much lately :D. The error you get is actually a warning which doesn’t affect the rendering of the shader at all.
Anyway to correct that please open the shader and modify this line:
half4 sum = half4(0.0);
to
half4 sum = half4(0.0,0.0,0.0,0.0);
I’m going to submit this fix to the asset store as well soon, but it doesn’t hurt having it here for reference as well.
The reason for which you are seeing the default pink shader is because my shader uses the GrabPass for taking the image behind it. GrabPass internally uses RenderTextures, which are a Unity Pro feature. So unless you have Unity Pro, I’m afraid you will not be able to use this shader. I’ll try to look into a workaround for this, but I’m pretty sure there is none.
I think Pro features are poorly signalled by the editor. It would be nice if Unity threw up explicit warnings when RenderTextures aren’t supported by the current license. I wrote the shader myself when i had the trial version of unity pro running and when only observed this when my license expired.
David
Posted at 22:25h, 15 MayHi Ana,
thanks for the info! I had hoped this was a possibility of getting a good blur shader without the pro version but sadly that doesn’t seem to be possible.
You should make a note in the asset store saying that Unity Pro is needed.
Cheers,
David
pengbitao
Posted at 06:54h, 11 Mayhi , really want to use your blur shader of unity3d. but after I tried it. I found that it cannot work on my computer. It says ““Program ‘vert’, incorrect number of arguments to numeric-type constructor (compiling for d3d11) at line 25. Same for d3d11_9x. ” hope you can help me to sovle this problem. thank you very much.
Ana Todor
Posted at 20:42h, 15 MayHello, please see the reply I posted above to a person who had the same problem as you did. And sorry for the late answer!
Eryk Pajewski
Posted at 14:24h, 30 JuneGreat example, thank you very much for shearing.
Will
Posted at 18:38h, 18 SeptemberHi There,
Im no expert when it comes to writing shaders so this question may come across a bit thick. But I would like to create a shader that adds blur to selective objects like you have without the mirroring that you have created to represent water. I really love this shader and can see it being used a lot in 2d games.
love u3d
Posted at 06:03h, 30 NovemberBlur shader (Pro Only) version 1.1 error? in unity 4.3.0f4 ,the Blur shader (Pro Only) version 1.1 be imported,but show “Material doesn’t have a float or range property ‘_blurSizeXY’
UnityEditor.ContainerWindow:InternalCloseWindow()
”
please tell me how to solve the problem