Motion Blur Matte Preview Refresh/Update Issue

Hi, first time user here. Mocha is a great handy tool but I’ve been experiencing some issues when working with the viewer with Motion Blur turned on. Most of the time mocha can’t update the viewer correctly when I try to view the extracted plate (i.e. the original plate multiplied with the motion-blurred matte). Depending on situations, any of the following three might happen instead of correctly showing the extracted plate:

  1. Shows white-on-black matte
  2. Shows previously cached matted plate (i.e. fails to update to new splines)
  3. Blank (i.e. skip the entire frame)
    I’m running Mocha on Windows 7 32bit on a machine with 4G RAM. I try to clean the RAM by restarting the OS but no fix. Since motion blur is crucial to a successful roto, being able to see immediate update on a matte when tweaking the splines is a huge deal. If there is a way to force refresh the viewer, it’ll probably solve the issue.
    Thanks for your information.

Ah ok. It should refresh automatically. Are you in hardware rendering mode in preferences?

Motion blur can be seen by switching the matte in your clip drop down then turning on the matte and turning off colourise (the paint bucket).
Because motion blur is calculated per change however, drawing will be slow as mocha has to refresh the motion blur per frame. Manual feathering is not an issue since mocha doesn’t have to work out the relationship of motion in the frames to create the blur.

Which version of mocha are you running?
It’s possible that there’s a graphics card issue as well. Try updating your drivers to the latest stable release.
Where are you storing the results folder for your project? Locally?

Ah yes, some of the system preference changes require restart. I should have mentioned!
Since you’re in the middle of production you probably don’t want to change, but be aware there is a 2.6.1 update available if you want to be on the latest version.

—Quote (Originally by martinb)—
Motion blur can be seen by switching the matte in your clip drop down then turning on the matte and turning off colourise (the paint bucket).
Because motion blur is calculated per change however, drawing will be slow as mocha has to refresh the motion blur per frame. Manual feathering is not an issue since mocha doesn’t have to work out the relationship of motion in the frames to create the blur.
—End Quote—
Thanks for the info. But the problem I have is that this motion blur calculation fails most of the time in the viewer. Is there a way to force Mocha to re-calculate a give frame?

Yeah, I did. But it doesn’t seem to make a difference though. Any ideas?

I think I’ve got it. Enabling Hardware Rendering does fix the problem. For some reason, the change in preference didn’t register until I restart my machine. Thanks a lot for your help, Martin.
I’m using Pro 2.5.2 by the way.