One-way motion blur

Support Basics & Interface
1

I’ve read the docs on motion blur, but I still have a question:

In the docs I see how you make motion blur, but the blur is coming and going. is there a way to make the blur just behind the movement of an object in a still image. I tried rendering the frame where the object comes to a stop, but then there doesn’t appear to be any blur at all.

Here’s another example:
In the docs, coming and going blur (O=object, /=blur, ->=direction)
////////O//////// ->

 What I want to do:
       ////////O ->

I hope that this is clear. Thanks for any help.

2

It’s just a matter of point of view.

Blender renders a number of frames over an interval of time and blurs them together to make motion blur. The interval of time starts from the current frame and has a length of the Bf parameter.

There’s no coming and going blur, it’s just a matter of perception as it’s always a coming blur (at the end of the shot, the object is always at the head of the blur trail).

I doubt that’s the answer you wanted though.

Martin

3

I did this once by tweaking the IPOs so the object was moving for the first half of the exposure time, and stopped for the second half, so it was much more exposed at the end of its path.
Or you could make a mblurred render and a non-blurred render of the final position and mix them together in post-pro.

4

Hi !

one of my firsts projects was an old airplane. I needed motion blur for the propeller.

As motion blur takes a long time for rendering, I used another method:

I duplicated the propeller N times with different alpha level, and delayed ipo curves.

This could be done with a character. More complicated though, if multiple meshes are linked.

Philippe.

5

it would be great if I could do that with motion blur :expressionless:

6

Yeah, the motion blur in blender is realistic. Just think about what’s happening in time and you’ll understand why. I think rouball’s method is the best if you only want blur in one direction.

7

yes, but lets take an example: when there`s a cube which moves from left to right from frame 1 to 10 and you render it on frame 10 there should be MBlur effect only on the left and there is nothing at all. why is that? or am I missing something?

8

Hi!

Yes, you are missing some thing, I think.

As motion blur in blender is an interpolation of 5, 8, 11, or 16 positions of your object (your cube) between two frames, you can’t get a motion blur effect rendering one frame (frame 10 in your example).

You have to set Frame 9 as start frame and frame 10 as end frame, and render in animation mode in image format. You will get frame 9 with motion blur and frame 10 without motion blur, but the cube will still be at the center of the blur…

For a still picture, I think that you could do a compositing of frame 9 and frame 10, using two layers in Gimp or Photoshop for example…

Philippe.

9

Do it this way kxs…

With pencil and paper, draw a lightly shaded square moving over 3 frames. When finished, the middle should be darker than the ends.