How to create wpf effects that extend outside the controls bounds?

Question

I've been fiddling with shazzam to create all kinds of cool PS effects but I still don't understand how an effect can affect areas outside the element its applied on, like the original blur or dropshadow effects for an exmaple. Can anybody elaborate?

Answer 1

By default the shaders are applied to a texture with the same sithe as the source control. But you can change this size by setting PaddingLeft, PaddingRight, PaddingBottom, PaddingTop properties on your ShaderEffect.

When your padding is > 0 both the input and output textures will be increased by this padding. So basically you won't have to make any uv transformations to take padding in account.