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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.

Thanks.

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    $\begingroup$ Use a mask instead ;-) $\endgroup$
    – 3pointedit
    Commented Sep 20, 2018 at 9:07
  • $\begingroup$ To rotate, connect the texure to a rotate or transform node $\endgroup$
    – sambler
    Commented Sep 21, 2018 at 9:03
  • $\begingroup$ @sambler Both of those methods end up clipping the texture to the dimensions of the image. Again, this is different to behaviour for material node. See here: imgur.com/a/2FINzvG $\endgroup$
    – d401tq
    Commented Sep 23, 2018 at 6:50

3 Answers 3

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Instead of using a gradient you can build a mask really quickly. Use the shift drag function to extrude a feathered edge from the shape. Invert the color of the mask using the little invert icon in the mask window.

defocus using a mask

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  • $\begingroup$ Thank you. I will give that a try. It would (as always) be nice if there was a procedural way to do this. $\endgroup$
    – d401tq
    Commented Sep 23, 2018 at 6:51
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    $\begingroup$ Well you can use the distort>lens distortion node, leave it in white, you'll get a fitted circle (circle edges touch all sides of the pros dimensions). Then apply a blur. $\endgroup$
    – 3pointedit
    Commented Sep 23, 2018 at 11:49
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Well you can use the distort>lens distortion node, leave it in white, you'll get a fitted circle (circle edges touch all sides of the pros dimensions). Then apply a blur.

distort node

Or for a perfect circle use a Bokeh Shape node with Rounding turned up to 1.000. Add a Scale node set to Fit, then blur or use Dilate/erode node set to feather

bokeh circle

And you can make variations of gradients using the texture Marble (in cycles or Blender internal), here I have made a rectangle that you can scale with the Less Than node.

marble square

Using this basic Marble texture

marble simple lines

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As far as rotating a texture in the compositor goes, you can use the "Rotated Texture" node group from this file:

Explanation here: https://blender.stackexchange.com/a/131433/68997.

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