Both of these work in a similar way - but be warned, they are quite limited.
Apply the filter to the layer you want to affect. Drag another image layer into the source well of the filter and the effect should now work. (You'll want to turn off the visibility of the source layer.)
The areas of the source image with the highest luminance will distort the destination image the most, the closer they values are to black the less influence they will have.
Some things to note though.
The position and scaling of the source image cannot be adjusted and will be assumed to be full frame (or if smaller than the canvas size will default to the bottom left corner (I don't know why).
If you're using a shape rather than a bitmapped image then the edges of the shape will be the only thing affecting the bump/displace so it's not really a very useful thing to do.
The displace filter looks more like a "glass" effect and you will get much more distortion from the bump map. Note also that the bump map filter pushes the image away along a chosen axis depending on the strength of the amount slider.
I would say neither effect give you the sort of result you might be used to from other applications.
Simon Ubsdell
http://www.tokyo-uk.com
