velocity pass all blurry!

[stezza]

I have gone through the documents on how to set up a velocity pass in after effects with RSMB vector.
But the pass when applied blurs everything in the scene. My camera is stationary just some moving objects flying by.
Does the grey background section of the velocity pass have an influence?
Thanks for any help.

[stezza]

User error.
I was rendering the last frame of animation which needed more frames forward to evaluate the velocity.

[hermit.crab]

Is the pass blurry or the effect after importing it? The grey area is the vector way of displaying 0, so it most likely isn't related to the blurring.

EDIT: Note to self, refresh tabs.

[stezza]

Hi Hermit, can you tell me if the velocity pass needs to be 32bit exr or is it simply the RGB in 8bit that's required for this pass to work.

[hermit.crab]

Both work (since vectors can be written as RGB), but I presume the technique depends on the post-processing software. In Nuke, the VectorBlur node asks you to select the vector channel, which can either be selected from the multi-channeled file or through the manually merged (via ShuffleCopy) .jpg as the Velocity channel.

[stezza]

Thanks Hermit, I was using a layer pass rendered as a png in After Effects with ReelSmart MotionBlur vectors plugin. I think it worked. I did have to blur the pass as it came out sharp edged. I had motion blur turned off on the physical camera as I wanted to do it in post but seems you have to have it turned on to blur the vector pass?

[hermit.crab]

I did have to blur the pass as it came out sharp edged. I had motion blur turned off on the physical camera as I wanted to do it in post but seems you have to have it turned on to blur the vector pass?

I think there's some kind of a misunderstanding. If you've decided to apply motion blur in post, the Velocity pass should be "sharp-edged". It works by writing down objects' XYZ coordinate changes between frames, which afterward are read in AE or Nuke through the Vector blur functionalities. Check this tutorial for RSMB.

[stezza]

OK so I think I have it all wrong.
I am creating a still image which has small pieces of geo flying by. These objects are animated from frame 1-20 but I am rendering out frame 10 as the final artwork. with motion blur turned off on the camera the velocity pass is sharp resulting in the interior of the object being treated as motion blur and not the outside, which is why I had to manually blur it.
I have set it up as per instructions but still doesn't look right. I haven't used this before so user error is in full swing!

[hermit.crab]

Not sure what's happening in your project. I just created a simple scene and added RSMB with a sharp velocity channel and it seems fine (although there is a bit of tearing, which the Nuke VectorBlur can remove through normalizing). In that case, why not simply render the motion blur with V-Ray?

[stezza]

Yeah your right I just thought it might be best to add in post, dont want to re render 8K image again. I will next time! Thanks for having a go.

[SonyBoy]

Honestly for a still image I wouldn't even both with motion vectors. You'd have more control just faking some blur in Photoshop.

[SonyBoy]

Hi Hermit, can you tell me if the velocity pass needs to be 32bit exr or is it simply the RGB in 8bit that's required for this pass to work.

Motion vector passes usually need to be at least 16-bit.