VRay Velocity and RSMB

[Mirko]

Hello,

I tried to use the VRay Render Element "VRayVelocity" to control motion blur in AfterFX via RSMB.

I have read some postings concerning the the Vray <-> RSMB workflow here in this forum. But it seems like I have missed an important detail. Because the blur goes into all directions throughout the whole image. And it is always at 100% even when there is nothing moving around in a frame.


Here is what I did:

- activating RenderElement "VRayVelocity" (VFB: off | clamping: off | ignor Z direction: on)
- rendering a frame where things are moving fast.
- the max velocity is 226,321. So I insert 230 into the "max velocity" value box.
- I then render out my animation (in *.png with alpha and RGB 48 bit)

- in AFX I insert my beauty layer into a timeline.
- I then place the velocity layer right above (but not visible)
- next, I add the RSMB Vector FX to my beauty layer and define the velocity footage as the control layer.
- "max velocity" is 230

The result is terrible.

Did I miss an important thing?

[rfellers]

Make sure the color depth is set correctly in the comp. In the project tab, look at the bottom and you should see the color depth - 8bpc is the default. The depth needs to be set at 16bpc. Also, make sure you turn off Color Management in 'interpret footage' for the velocity clip.

Personally, I save the element in the vrimg, then run a batch script that extracts the individual elements as EXR. Not sure if this process will work the same on PNG.

As a side note, if you are saving the images at that 48-bit color depth just set the max velocity to 2048. There is plenty of depth there to capture all the motion.

Ryan

[Mirko]

Hello Ryan,

thank you very much for your advice. I have checked/changed the bit depth and the color management in AfterFX (see screenshot below). But at the end, nothing has changed, yet.

I have rendered a small video example:

http://www.mirko-heimburger.de/rsmbtroubleA001.wmv


I have never used 'vrimg'. Maybe I should have a look at it.

[rfellers]

I would guess there is something wrong with the gamma on the velocity PNG that is shifting the values on you. Make sure you save it in linear space (gamma = 1.0).

I just tried a simple test using your PNG method and it seems to work okay for me...

[Mirko]

I would guess there is something wrong with the gamma on the velocity PNG that is shifting the values on you. Make sure you save it in linear space (gamma = 1.0).

Aha - that's a good hint! I am never sure if my gamma settings are right or not. Attached you will find a screenshot of my gamma settings. Should I activate "Override Gamma: 1,0" at the velocity output then?

[rfellers]

Yes, you can either override the gamma to 1.0 in the save dialog(best solution), or you can try correcting the gamma in AE(might not be as accurate). To do correct it in AE, create a new comp and put the velocity clip in it, then apply a exposure filter with a .455 gamma level. Next create another comp and put the color clip and the velocity comp in it. Use the velocity comp as the target for the RSMB plugin.

To make sure your values are correct on the PNG, render a static scene (no moving objects) and look at the velocity channel in AE. Move the mouse over the footage and check the info tab - the color should be exactly 50% grey. Mine says 16384 in each channel (range is 0 - 32768 ).

[Mirko]

Thank you very much!!! I will try that tomorrow.

[Mirko]

THANK YOU rfellers!!!

You had been right about this gamma thing! Now it works (almost) fine. Thanks again for your help!

I do still have some strange issues with the RSMB blur. But I think that comes by it's nature (2D moblur fake).

[stevesideas]

If you check out this thread you will get plenty of information:

http://www.chaosgroup.com/forums/vbu...al+motion+blur

I use RSMB and the motion blur is without issues once you nail down the process.