difference of vrayvelocity and exr-velocity?

[thomes]

hello,

whats the difference between vrayvelocity render element as 24 bit .png and the velocity embedded exr. file 32bit FF ? working in vray 2-4004
i read that the zero point is not 0 but 0,5 but this can be controlled in AE by editing the black- and whitepoint
are there differences in AE (with REELSMART MB) if i render out velocity included in the 32bit exr?

thanks
thomes

[tashko.zashev]

Hi Thomes,

If you save the image in exr (32 bit) or .vrimg format velocity channel will be 0 based.
For 16 or 8 bit image it will be 0.5 based.

Some compositing applications works with 0 based others with 0.5 based, V-Ray supports both of them.
If I remember it right, REELSMART in AE works with 0.5 based velocity.

[thomes]

thanks tashko for your response.

i was told that the result in AE-reelsmart is not of the same quality if you render only 24-bit png. with the 32 bit exr it gives much much better motionblur results in reelsmart.

can anyone second that and tell me why?
if i find the time i will do some tests to confirm that.

[Rens]

If you save the image in exr (32 bit) or .vrimg format velocity channel will be 0 based.

I think this is only when you save an image through the raw image format, vrimg or exr. It'll be 0.5-based when you save directly from the vfb window, through the max output, or through split render channels.

[Rens]

i was told that the result in AE-reelsmart is not of the same quality if you render only 24-bit png. with the 32 bit exr it gives much much better motionblur results in reelsmart.

can anyone second that and tell me why?

Rendering 8-bit PNG won't be as good as 16-bit EXR and 16-bit EXR won't be as good as 32-bit EXR.
It's because of the range, you get more 'motion' or precision in a larger format, for small motion you won't need 32-bit though. If you have very fast moving objects you will get stepping and artifacts when using 16- or 8-bit.

[wxyz]

How do you alter the black and white points to convert the zero point to 0.5?

hello,

whats the difference between vrayvelocity render element as 24 bit .png and the velocity embedded exr. file 32bit FF ? working in vray 2-4004
i read that the zero point is not 0 but 0,5 but this can be controlled in AE by editing the black- and whitepoint
are there differences in AE (with REELSMART MB) if i render out velocity included in the 32bit exr?

thanks
thomes

[thomes]

http://www.timsportfolio.co.uk/tutor...-pass-3ds-max/

[wxyz]

thank you sir

[stevesideas]

On the same topic, I'm still having issues with RSMB and vray velocity channels when using after effects.

I've attached an image of the velocity channel and the still. Then when I use RSMB with the velocity channel. I've followed the instructions on the link Thomes provided above by turning off linear light for the velocity. The result is odd and I'm not sure what to do now !

Both are screen snips and just for viewing. Can anyone help ?

The camera is quite low down and moving quite quickly across a water surface. It gradually pans up. At this stage it is low and moving quickly. Max displace in vray velocity showed to be around 175.

[stevesideas]

and this was the result when using RSMB.