I have a rendered image (actually sequence of images) and want to 'fake' a depth of field in the compositor by using a blur, or a defocus. My preconceived notion was that I should produce a gradient texture and use either the blur node and a color mix to combine the unblurred and blurred versions according to a factor prescribed by the gradient texture, or use a defocus node with the Z factor prescribed by the gradient. However, this seems much harder than it should be for the following reasons:
Creating a texture for the compositor seems hard - the only way I could find to do it was switching off Cycles and into BI, creating a new texture, and then switching back.
When using a Blend texture in the defocus node, it seems very hard not to get a sharp 'edge' where the blur 'turns on'.
Most confusingly, it seems impossible to rotate a texture in the compositor. In the node editor for a material, this is trivial, but I can't see how to do it here.
Any advice regarding the above confusion, or on a better way to achieve my goal, would be greatly appreciated.