Red Epic Motion blur

[shadevfx]

Hi all! Has anyone had any experience matching V-Ray's mb to red epic footage? Everything's shot at 180 degree shutter, as per the usual, but for some reason when we render with mb it's making our tracks look really off.

Haven't experienced this with other formats. Any thoughts?

thanks!

[joconnell]

Just as a quick thought is there any chance you've got your motion blur interval center at 0.5? If so your cg will be half a frame out of sync with your track. Otherwise it could be rolling shutter artifacts.

[shadevfx]

yes, that was a big part of the problem... set it to 0 and .5 and it started to feel better.... .4 seemed even a little closer.

Thanks!

[joconnell]

if you use the default interval center in vray, the movement of your object is centred around the movement between one frame and the next - it's kind of like instead of render frame 0,1 and 2, you're actually rendering the object's position at frame 0.5, 1.5 and 2.5. This is all well and fine for normal animated scenes since an object needs to come from somewhere and have somewhere to go to generate motion blur. The issue is when you start 3d tracking, your trackers are locked to the objects position dead on each frame with the motion blur centred around each full frame. If you use the default interval centre your objects will lag behind your track and appear to be chasing it, or on more gentle tracks appear to be a bit slippy / wobbly. Glad you're getting a better result though!

[shadevfx]

yes that seemed to be it.

Is there a way to adjust this when using the physical camera? Or will it grab the settings from the render globals?

thanks again!

[joconnell]

That's a very good point, I rarely use the physical camera for tracked stuff since most matchmove programs will output a standard camera. I can't say this for certain since I've never used it in production but setting the physicam to movie cam mode will enable both shutter angle and shutter offset - I'm not sure if -90 or +90 is the value to use in the shutter offset but I'm guessing that's where you should be looking.