MIP Motion vectors - How?

[Chris_TC]

I hate doing motion blur in post, but right now I have to. I'm using the MIP motion vector output shader, and the resulting images are wrong as far as I can tell.

I've got a camera moving down a hallway, so the entire frame is moving. However, there are areas in the motion vector frames that are completely black: RGB 0,0,0.
After looking at the red and green channels I can see what the problem is: the red channel (which stores X displacement) only has values in the left half of the frame. The right half is black.
The green channel (which stores Y displacement) only has values in the bottom half of the frame. The top half is black.

Should these values actually be NEGATIVE? Do I have to render to 32 bit format? If so, then why do you even have the option of rendering to 8 bit or 16 bit? The manual only says that 8 bit is not recommended. I'm using 16 bit, and the results are wrong. Could somebody shed some light on this?

[Hirazi Blue]

In which compositor do you want to use the Motion Vectors (& what is your "Floating Point Format")?

[Chris_TC]

Using Fusion. I now tried TIF float and EXR float. They seem to give negative values, but Fusion reads those parts of the frame as color value "-1.#INF" and does not motion blur them. So I guess this is incompatible.

All of this was using the floating point RAW mode of the mip motion vector. When I use floating point Off, the values appear to stay within 0 and 1. But they must be wrong because all I get when applying them in Fusion is a uniform diagonal blur across the whole frame.

I also tried the la maison shader, but if I drag it into the render tree and try to render, I get a warning that tells me "shader not found". What a hassle, should have used the rasterizer like I usually do.

[Hirazi Blue]

Seems to me, some of your settings in Fusion might be off.
Can't help you there, I'm afraid...
Sorry

But concerning the "la maison shader": you did get the 64 bit dll and spdl and install that correctly
(I'm assuming you're "on" x64)

[Chris_TC]

Ooops, I think I might have gotten the 32 bit version. Thank you, I will try this.

[Rork]

I can recall something similar on the xsi mailinglist some time ago. It had to do with inverted vectors or something.

Might be worth a shot.

rob

edit: found it, search in the xsi mailinglist archive's for Vahan Sosoyan's 'mip_motion_vector workflow" thread.

[Chris_TC]

Vahan Sosoyan's 'mip_motion_vector workflow" thread.

Oh wow. It works! And it works really well. Thank you so much!

[Rork]

it wasn't exactly what I was thinking of, but hey... at least I was in the ballpark, and it works

happy comping!!