DoF and Motion Blur using Compositing Nodes

I have been working on a digital painting by setting up the scene in 3D beforehand. I am currently stuck trying to get the blur and DoF settings right and with a believable scale.

My vision is have the camera focused on the ship as you will see in the picture I attach to this post. I want the ship to be clear but the second ship and the background to be blurred so as to give off the idea that the ship is moving at a fast rate of speed. I cannot seem to get the picture to look right. I was hoping someone a little more experienced could help me with my problem.

The camera lens is at 17mm, and the settings in the Defocus node are as such:

Bokeh: Octagonal Angle: 90

fSTop: 100
max blur 10.000
threshold 1.500

I am using the defocus filter in my nodes as well. Thanks.


Two immediate, visceral reactions:

  • The relative scale of the two objects appears entirely wrong. An object that is farther away and moving at a high rate of speed would be considerably smaller. (And, even though this doesn’t really happen in “deep space,” you often see distant spaceships being portrayed with the “lower color saturation” that comes with atmospheric distance. (I even saw a film in which, at the heat of an emotional moment, they’d added “heat haze.” Maybe the editor had just finished a cowboy flick…)
  • The amount of the effect probably should be a function of z-distance: the farther away the object is, the more pronounced the effect. (A ramp-node is a very good way to give yourself fine-grained adjustment of this…)

I presume that you are rendering each of these things separately. Be sure, then, to output everything in the MultiLayer file format. Generate the complete final-product in this way, then (separately…) generate the movie-files for display purposes.

Regarding motion blur: the background would appear blurry because the CAMERA is moving to follow the ship. However, your ship is moving towards the camera (as opposed to flying sideways, like you’re looking out the car while driving). I suppose the camera could be moving backwards to follow the ship, in which case the blur-lines would be converging somewhere near the center of the image.

So how exactly would you suggest that I render the blur lines for the image. Should I post up an Empty in the middle of the scene and then focus the depth of field on the camera towards that? and what mm lense should I be using for the depth of field. 17 seemed good enough.

If you want to use the vector blur node, then things need to be moving – as that’s what generates the vectors for vector blur. The easiest thing would be to have the ship moving, and parent the camera to the ship, so it’s moving the same amount.

Another option would be to apply some motion-looking blur in Gimp or Photoshop. This, for instance, was done by creating a quick matte for the ship, then applying a zoom blur (in Photoshop) to the background:

A third option would be to use “sampled motion blur” in blender but it can take a very very long time (it renders out a complete frame for each sample, and you’ll probably need 11 or 16 samples to make it work).

I see. So far my options aren’t looking to great but after giving the sample motion blur a shot I think I will play with it some more, but will prolly just end up using gimp for the blur. Thanks for all the help though.

this “zoom-blur” can also be done in blender itself. i had some struggle with applying a alpha mask to make it only effect the edges and decrease to the image center but it works