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I'm writing a 2D hack-and-slash game using XNA. I really want to implement the blur-like, refractive effect of a sword or such moving really quickly, seen in such games as Dust: An Elysian Tail and Vampire Dishwasher. Anyone know the technical name for this effect? For those who aren't sure what I'm talking about:

enter image description here

shows exactly the effect I'm trying to achieve.

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up vote 3 down vote accepted

The XNA education catalog calls it distortion. Kind of a catch-all term, but it fits.

enter image description here

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for a wider and more explained paper, take a look at this: GPU Gems2 - Chapter 19. Generic Refraction Simulation I would try to do the same. In 2D it's easier! – Gustavo Maciel Jul 9 '13 at 6:08
@GustavoMaciel That is worthy of it's own answer. I would also recommend water caustics from that same GPU gems series. – Seth Battin Jul 9 '13 at 14:04

it remember me to magnifying effect i'm used to do long time ago in vga 13h mode... using the bresenham circle algorithm to get the lines that draw a circle and applying a function to the distance from the pixel to the circle center to peek the color based in the new distance from a backbuffer where the original image was.

Now it can be accomplished with an hlsl postprocess shader easier.... you can google for radiul blur... or pinch effects and it will give you something near to what you are looking for...

Here you have a sample where you can test this kind of effects:

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