How do I add a shader effect to the camera?

[Yue]

The idea is that when my character runs out of energy add a grayscale shader. In the editor I know how but I need through scripts. I appreciate an example, because what I have doesn't work for me. 

 

function Script:Start()
    local shader = Shader:Load("Shaders/PostProcess/grayscale.shader")
     self.entity:AddPostEffect(shader )
end

 

[Josh]

Cast the entity to a camera object to access that function:
https://www8.cs.umu.se/kurser/TDBD12/VT04/lab/lua/tolua++.html

See tolua.cast.

[Yue]

Ok, I already have it, however I don't know how to delete it, I have an option to delete all of them and not one specif

[gamecreator]

I don't think you can remove individual shaders.  You have to remove all of them and add back the ones you still want.  Related to this, remember that you can add the same shader more than once so removing them by name would not make sense.  I guess removing them by an index could work but it's not too bad to clear all and re-add.